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Astrophysics - Science topic

Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior.
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Physics is one of the physical sciences. The two other physical sciences are chemistry and astronomy. Astrophysics is the branch of physics that deals with space and celestial bodies.
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Weitter Duckss "Astrophysics today (and before) is a fabrication of nonsense. "Scientists" (based on astronomical observations) fabricate their results without evidence (mostly)".
"When are lies and nonsense removed from the classrooms?"
You haven't posted a single thing to substantiate any of those wild allegations.
What is your problem with those lists you posted of exoplanets, brown dwarfs & stars?
What is your problem with the contents of the paragraph you quoted from Jim Kaler's http://stars.astro.illinois.edu/sow/star_intro.html ?
Please be specific.
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Carroll and Ostlie in An Introduction to Modern Astrophysics, second edition at page 1099 remark: “Cosmological redshifts are caused by the expansion of the space through which the light travels, so for extremely large distances the total elongation of the wavelength depends on how the expansion of the universe has changed with time.” The 4/3 laws are based on dimensional capacity and imply a distance in 3 dim space stretches by 4/3 compared to the same distance in 4 dim space-time. Is there a connection?
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  1. A. Chubykalo , A. Espinoza , V. Kuligin, M. Korneva. Once again about problem“4/3”. International Journal of Engineering Nechnologies and Management Research. Vol.6 (Iss.6): June 2019, ISSN: 2454-1907 DOI: 10.5281/zenodo.3271356
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It may be a binary black hole accretion disk or an AGN.
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Thank you very much Sriram for the paper link you shared. The reported value of 33 G for V404 Cygni is significantly low. The paper itself mentions that the for other sources such as Cyg X-1, the range of magnetic field is ~10^5 to 10^7 G (My theoretical paper also suggests that this range of magnetic field can be acheived in a magnetically supported disc around a black hole. Ref: Sarkar B., Das S., 2018, JApA, 39, 3)
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Can anybody please share the IDL source code for Hapke photometric modeling?
Thank you,
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Hi! I don't know if it would help but this article is about hapke modeling calculations with IDL.
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Dear Sirs,
I think many knows the ideas due to Jules Henri Poincaré that the physics laws can be formally rewriten as a space-time curvature or as new geometry solely without forces. It is because the physics laws and geometry laws only together are verified in the experiment. So we can arbitrary choose the one of them.
Do you know any works, researchers who realized this idea. I understand that it is just fantasy as it is not proved in the experiment for all forces excepting gravitation.
Do you know works where three Newtons laws are rewritten as just space-time curvature or 5D space curvature or the like without FORCES. Kaluzi-Klein theory is only about electricity.
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??Preston Guynn. added a reply on June 19, 2019:
Force, mass, and energy are a parallel set of descriptions of the effects of special relativistic Thomas Precession. All matter and space, and their interactions are described with distance in three dimensions, time, and their derivatives.
Newton's first law of motion is , "Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it."
Yet the concept of motion requires at least two objects, and if there are two objects, then there is always an external force, which is gravitation.
So the idea of rewriting Newton's laws without force (or mass or energy) is good, but it should be extended to incorporate the most basic non-linear effects of motion in space time, which are special relativity and Thomas Precession.
See my article describing the recent discovery of the effects of Thomas Precession the particle and galactic scales.
Article Thomas Precession is the Basis for the Structure of Matter and Space
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Dear Sirs,
I would like to find out more precisely whether the 2nd Newton law is valid or not in wide range of masses, accelerations, forces. Particulary I have a question whether the inertial property of body (inertial mass) is able to stop the body for small external forces or not. I have found in the Internet the fresh articles with tests of the 2nd Newton law for small accelerations (10^-10), small forces (10^-13) and SMALL masses (about 1 kg). The articles deal with the question of dark matter and MOND theory in astrophysics.
But I am interested in BIG masses. Could the test be carried out in planetary scale? Maybe for the Moon or asteroids? Or for masses like 1000 kg? Thank you very much for any references.
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As per the Newtonian inverse square law, it is applicable only for point objects;
This law, as an extreme case, is therefore applicable for objects of any geometric kinetic property
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astrophysicst
What is the role of anisotropy in the dynamic modeling of star. For realistic modeling of star what should be the trend of anisotropy from center to boundary.
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Following.
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Some petroleum and geophysics companies use controlled-source seismology for Mineral Inspection and cavity detection. These methods based on impulsive source controllers such as (dynamite, air gun seismic source, etc.). More efficient techniques use a Seismic vibrator for seismic wave generator such as chirp, sine or square seismic waves.
I wonder if recents detections of Gravitational Waves coming from earth or space using optical interferometry, and how to distinguish between each of them, especially when seismic wave have a same chirp form such as Gravitational Waves?
Example of Seismic Source: http://seismicsource.com/html/index.php
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Go to https://gracedb.ligo.org/superevents/public/O3/ You will see lots of candidates, 56 to be exact. Half of them have been rejected. The rejected ones, have shape of gravitational waves but turned out to be noise from other sources, such as cleaning equipment. Many "confirmed" ones were detected only by one detector, such as GW190425 (the only confirmed detection from the 3rd run) or GW170817 ( the only one supposedly with a visual). LIGO mistook different types of noise for grav waves before so nothing can be ruled out.
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If global warming cannot be resolved by controlling/minimising gas emissions, then extraordinary measures may be the only viable options, one of such ideas is placing a solar shield between the sun and earth at the L1 lagrangian point to obtain a reduction in solar insolation . It may sound crazy, more like science fiction to know that a disk of 2000km in diameter would be necessary to reduce solar radiation reaching earth by 1.7%. I wonder about the sort of stresses that would be experienced by such an enormous body. Also, what sort of materials' properties would be required to withstand the conditions at L1, for example solar radiation, other rays. While it is possible to calculate the disk's orbital velocity around the sun, its angular velocity (around its axis) is difficult to calculate. I would be grateful if those with relevant experience could share their thoughts about how such calculations could be achieved.
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The following article is relevant:
This paper presents a novel method of space-based geoengineering which uses the mass of a captured near Earth asteroid to gravitationally anchor a cloud of unprocessed dust in the vicinity of the L1 position to reduce the level of solar insolation at Earth. It has subsequently been shown that a cloud contained within the zero-velocity curve of the largest near Earth asteroid, Ganymed, can lead to an insolation reduction of 6.58% on Earth, which is significantly larger than the 1.7% required to offset a 2 °C increase in mean global temperature. The masses of the next largest near Earth asteroids are found to be too small to achieve the required level of insolation reduction, however, they are significant enough to be used as part of a portfolio of geoengineering schemes.
Cheers
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Hi everyone,
I am studying MSc Astrophysics and my supervisor informed me last year that I would need to know Python to create plots in order to analyse data.
So I had started watching Python videos but when it came to using it for Astrophysics it turned out I still had not learnt anything. Being new to Python I had been 'learning' it in the ways of building a website and not for Astrophysics.
It's not applicable to what I am working on.
Long story short, I have been given some code to work with for analyzing chemical abundances in dwarf galaxies in the MW Galaxy. I feel I am learning by trial and error and ideally I would like to replicate scatter plots that I have seen in research papers but using my own data.
Is it possible to 1.) Know what programming software/language a scientist has used in their paper and 2.) Is it possible to get the code (the structure/layout) more than anything else?
I'm teaching myself Python and whilst everyone says it's easy compared to other programming languages, this is my first and therefore no comparison: just a lot of libraries that do many different things. I am finding it rather frustrating and need a "all you need to know" book on Python for Astropysics.
Equally if anyone knows any helpful resources I would be very grateful. Thank you!
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I would advise you to use Matplotlib as Richard Epenoy suggested or even Seaborn which are both Python libraries for plotting data. Getting the very same Figures may not be straightforward but Matplotlib is very well documented and Stack Overflow has fixed me countless problems. Moreover, you may find the code for a given Figure in the supporting information related to the research paper (for instance we did so in 10.1002/jcc.26157).
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What we actually mean by "Dark Matter Energy" in layman language?
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Do you have any good abstract for this topic in your mind? Please feel free and share with us.
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Dear Colleagues,
I am a liaison (informal) at my university between science and the arts. I have family in planetary astronomy but this is far afield.
A question or two:
What does this newly-reported Radcliffe Wave of gaseous proto-stars tell us about how our galaxy originated?
Is there any chance that this wave will make some difference in our own sun's behavior?
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Dear Preston,
Intriguin view, thanks for sharing Vera Lima
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I was once told that stable isotopes of lighter elements such as H, N C , etc are found in stars, planets, etc. Can anyone suggest any literature which talks about the formation of these isotopes?
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The lightest elements (mainly hydrogen and helium and in trace amounts lithium and beryllium) were formed about 100 seconds after Big Bang through the Big Bang nucleosynthesis (this process lasted up to 20 minutes after Big Bang).
After the formation of stars new elements, from helium to iron, are produced in stellar nucleosynthesis (thermonuclear fusion: CNO cycle, proton–proton chain reaction and triple-alpha process) during stellar evolution.
Elements higher than iron are produced in supernovae through the r-process and s-process.
A very good book about this and generally about properties of stellar interiors and the structure and evolution of stars is: "The Physics of Stars" A. C. Phillips.
About the nuclear physics of stars, you can see also a book of Christian Iliadis "Nuclear Physics of Stars".
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Does the New Astronomy Journal charge fees for publishing accepted papers? Are there any page charges?
Or is it totally free like Research in Astronomy and Astrophysics Journal of IOP or Journal of Astrophysics and Astronomy of Springer?
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Hi, you don't need to pay to publish a paper in New Astronomy as it is the case for all Elsevier journals. Neverthess, if you need the paper to be available to everyone you need to pay (see attached document).
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There are some Computational fluid dynamic numerical simulations available like John Hopkins CFD numerical simulations database is available to use. Is that can be used for Astrophysics purposes?
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[I am not the right person to answer your question but this might help]
Two kind of CFD methods are more popular in Computational Astrophysics, compared to Mechanical/ Chemical/Civil engineering CFD, and there are solid reasons for that:
1) Smooth Particle Hydrodynamics (SPH) method. It is developed in first place for astrophysics and due to its Lagrangian nature it can tackle questions of astrophysics very nice.
2) Spectral Methods (I do not mean spectral FEM, I mean methods such as Chebyshev polynomials spectral method): Those methods are of very high order and they are computationally effective and suitable for "large" domains of astrophysics, on one hand; On the other hand, in astrophysics we are not dealing with odd and dynamic geometries of the domain and this fact eliminates one of the main limitation of spectral methods.
Hope it helps,
Kaveh
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What are the major unsolved theoretic problems on the astrophysical dust molecular clouds and their evolutionary dynamics?
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Thanks a lot for positive feedback
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We can direct this question to astrophysics scientists, theologians, philosophers, scientists thought and civilizations! why?
Astronomy shows that the universe is very wide and the distances between the planets are very far away, especially those distances between solar groups or between galaxies. So, for now, humans can not get out of the earth and settle outside.
Nor have we found references in religious beliefs about the possibility of humans coming out of the earth.
As well as philosophy scholars did not deviate from the geographical framework of the Earth!
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Surely no
Best Regards Nasser Farhat
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It was amazing to see the very first image of a black hole. I'm not expert in the field of astrophysics, but in the interest of AI, I think the image is worth to be discussed more. I have made a blog to explain my point of view:
Agree? Disagree?
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Hi,
yes i agreed..
The Event Horizon Telescope (EHT), which uses a network of telescopes around the globe to turn all of Earth into an enormous radio telescope, has taken the first direct image of a black hole. There is general consensus that supermassive black holes exist in the centers of most galaxies. Despite its invisible interior, the presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation such as visible light. Hawking showed that quantum effects allow black holes to emit exact black-body radiation. ... This radiation does not come directly from the black hole itself, but rather is a result of virtual particles being "boosted" by the black hole's gravitation into becoming real particles.
Best Wishes..
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Astrophysical S-factors for thermonuclear reactions that produce electron neutrinos.
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Good morning Dr. Fontana.
Thank you for your information, I appreciate it. I have been reading the article you just shared and it is really helpful. I was wondering if you have some information about the Astrophysical S-factor when it is evaluated in the gamow peak (S(E_0)). I checked a couple of articles and they had the value for some neutrino reactions, but not all of them. I have e.g. p + p, but they do not have the rest of them. I'd appreciate it if you may give me a hand with this, because I've been stuck at this and also need an expression for events number in a solar neutrino detector.
Thank you very much.
Best regards.
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To publish a Unified Theory of Everything, which includes a series of papers describing and proving its Astrophysics, Electromagnetics & Optics, Gravitation, Weak Force, and Strong Force counterparts, what would be the best Scientific Journal to publish it altogether, or is it better to publish it as a book with chapters covering individual proofs in different physics disciplines? If submitting to a Journal, how can the intellectual rights be protected in the peer-review process? If published in a book, what would be the pros and cons in comparison to being published as an Academic Journal Paper?
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Dear all,
in accordance with Friedmann-Lemaitre-Equation there are three different possibilities of space curvature which can be described mathematically and imparted graphically or analogously (Closed, Openend or Flat Universe). In the attached poster a fourth graphic representation is shown, which is however only graphically derived.
Is this sketch describable within Friedmann-Lemaitre-Equations? How can we interpret this sketch? A Universe that is truly infinite, although it has a defined start and a defined end point?
What would be a 3-Dimensional mathematical object to describe the plot (closed hypertorus, while closed means without a connection in the center?). And what numbers for curvature parameter k and density Parameter Ω make sense for this sketch?
I have created this plot purely graphically and wonder whether a mathematical interpretation of such a shaped space-time is possible, or whether it inevitably leads to paradoxes and is thus a graphic that can be drawn abstractly, but ultimately makes no mathematical sense.
Thank you!
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I might add that my paper on a "Bipolar Model"...of hyperbolic space was rejected by Physics journals as being too mathematical and by Mathematics journals as being too physical. It primarily raises the question of what coordinates are "physical". This is not easy to answer. For example rotating coordinates are considered non-physical, but if you are in them, they are real and there is physics associated with them. As mentioned above, one needs to consider the matter distribution to make sense of them.
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the gravitational waves are travels through the universe with the speed of light and it is the disturbances/ ripples in the fabric of space-time. as observe in the electromagnetic radiation light is decays/redshift, similarly in the case of gravitational waves curvature of any massive astrophysical objects affects or deacay it???
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Gravitational waves decay like EM, so the power falls as r-2 in free space, but LIGO measures only the strain which is like just one part of the EM field so that falls as r-1. That
The waves couple very poorly to matter so it has no dissipative effect and is essentially transparent to them but they are affected by gravity in the same way as light so subject to gravitational bending and the Shapiro delay for example. Weber Bars were constructed in such a way that they resonated at a specific frequency but could only extract any energy over a very narrow frequency.
Keplerian orbits can be assumed when the bodies are far apart and the waves frequency from that period tells us basic properties like the chirp mass and luminosity distance. Non-linear effects are very important in the strong field region which occurs close to the final merger and decades of work on supercomputers was required to create the templates predicted by GR which can be used for comparisons and extraction of additional parameters like mass ratio and spins.
You can discount any criticism that LIGO didn't detect waves, they published the exact location and range of GW170817 some 12 hours before it was found and that was what allowed the successful highly targeted search by SWOPE. The range given meant they could examine just a handful of galaxies instead of thousands in the area of the sky and subsequent optical measurements confirmed their figure was accurate to within 5%.
There are a lot of people out there with "theories" that said waves couldn't exist who now have trouble dealing with reality.
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Kepler-186f is the first earth-sized planet located in the habitable zone of another star that has been discovered. With this discovery, the search for life on other planets has entered into a new zone of discovery.
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Nice discussion...
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This question relates to naturalistic explanations, because they can approach to the reality or retreat from it with time.
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Dear Thierry,
For me, it is surprisingly that nobody writes that the science destination is the improvement of the living conditions, life prolongation, and notices on the possible dangers from nature. Meanwhile, just such main pursues we have for an object when aspiring to reveal the mechanisms of natural phenomena. For example, the LOH-Theory is aimed at understanding of the causes of aging of organisms, optimal nutrition, and ways of life prolongation. It was written that, in ancient times, people could live for a long time, and we believe that the quality of life could be significantly improved and life could be prolonged, and we propose possible ways to do this:
From the same theory, it follows that not proteins but DNAs are determining for life and, therefore, when developing the artificial nutrition, it is necessary to remember that the nutrition should be chiral and should include P(+5 valent) and N(+5 valent) and C(-4 valent) (unfortunately, some designers of artificial nutrition don’t take these rules into account.
When developing the understandings in the fields of catalysis and related phenomena (for 60 years), we aspire to upgrading and reduction technologies in their costs through understanding of the phenomena rather than through formulation of arbitrary models.
Our theories have an important feature: all they have real observations or measurements rather than assumptions or so-called models in their ground. "Accurate" scientific conclusion should, in my opinion, have no model or assumption in its basis.
I think and even I can write that I am sure that people always will be mistaken in their extrapolation of the natural phenomena or processes outside the really measurable or observable fields, if the mean of the extrapolation has a model (an assumption) in its ground; the mistakes can be revealed not immediately but sooner or later they will be revealed. I am convinced that, in our time of the occurrence of a majority of available real measurements and observations, the models are the whip against science, although they so far remain to be useful in the area of engineering.
When developing the PFO-CFO Theory, we bear in mind to warn people well in advance about possible dangerous events from the Sun, because who is prevented, is armed.
The PFO-CFO theory doesn’t allow knowing when and by what way the natural laws were created, but we believe that, being once created, they can’t be violated; according to the PFO-CFO Theory, the Universe beginning was not infinitely long ago but the actual time of its beginning is unknowable for people.
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A three-dimensional (3-D, nonplanar) geometrical configuration of astrophysical fluids could be conveniently visualized.
What is a justified way to visualize one-dimensional (1-D, planar) geometrical configuration of dust molecular cloud fluids in astrophysics?
What is well represented by the single spatial variable, x, in this context?
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In continuation, it is well known that a spherical (3-D) problem (with total degree of freedom # 3) could be reduced into a radial (1-D) problem (with total degree of freedom # 1) at the backdrop of spherically symmetric geometry. In both the cases (3-D + 1-D), the radial coordinate, r, can be well visualized in a sphere.
The same problem for analytic simplicity can also be worked out in a planar cartesian geometry (1-D). In this case, what does the cartesian position coordinate, x, represent? Is it possible to draw a crystal clear pictorial visualization of the latter in reference with the former under the condition that r=x if and only if (1/r)~0?
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The constitutive dust grains in astrophysical environments are partially ionized. What should be the most appropriate (effective) form of dust-dust interaction in astrophysical environments? In a broader sense, how should we improve the existing models in the above light?
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The charged dust-dust interaction is electrostatic in origin. What is the expression of the interaction potential?
Reply and reference are welcome.
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Astrophysical fluids are nonthermal in nature. Could you please provide a list (preferably, tabular form) of various nothermal distribution laws for the constitutional particles relevant in large-scale astrophysical fluids?
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An appropriate answer to the above question is kindly requested for your needful action as early as possible.
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Can any body name some astrophysical fluid instabilities still lacking theoretical explanation?
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All are kindly requested to answer this question with full energy
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Paranomal Research should be considered research, we all understand that, but what kind of research? What branch?
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Paranormal research is by name a kind of research. But this does not imply it is scientific research that falls under any branch of science.
In fact, by definition it is not scientific because "paranormal" is something that "cannot" be explained by science. Science is the effort to explain things that "haven't" been explained yet.
Though, in principle, you could have branches of science studying "paranormal beliefs". For example, Psychology can study why a person holds such beliefs and how that affects its phyche: usually conspiracy-theorists and "paranormal researchers" are feeling that they hold a special place due to the fact they're "out of the norm." Sociology can study how these mechanisms manifest to groups of people, or History can record such behaviors.
Any definition of modern science and the practice of scientific method, rule out the notion that paranormal research can give testable scientific theories supporting that there are "paranormal" phenomena.
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At the dawn, of the 21st century during a reign governed by money and greed the buzz in the economic and technological race was to build an economy based on hydrogen. A couple years later with the financial internet crisis of 2001 all this buzz disappeared and we entered a reign of terror and war governed by a different type of ethics…
Now, we are facing a different challenge: the climate change due to the over consumerism and accumulation of pollution since the 19th century. After decades of foolish hard geo-engineering experiments scientists, engineers and technologists have to come up with all kind of ineffective “solutions” (some are doing worse than good) to master the astronomical forces involved in order to control the effects of climate change and continue business as usual…
Hydrogen is seen as a non-polluting way to store renewable energies and nuclear energy since its recombination with oxygen produce only pure water. It is a transportable fuel for vehicles and other tools and devices running on electricity.
Further, some scientists fascinated by the solar nuclear energy (“illimited source of free energy”) have convinced uneducated deciders that the ultimate goal was to master the nuclear fusion and build an experimental international power plant called ITER.
Please, justify your position by sound arguments.
Thank you in advance for your esteemed expert contributions and for your understanding.
Kind regards.
No personal attacks, insults, pollution of the answers with popular press clippings from other discussion will be accepted.
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I agree with Dr. Dariusz Prokopowicz
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The derivation of orbital velocity is presumably well understood. One method is to set the centripetal force equal to the gravitational force and solve for v.
Mv^2/r = GMm/r^2
for which orbital velocity becomes v = sqrt(GM/r)
Now let's assume we have a spacecraft in stable orbit around a body at some distance r(1) and want to move the craft to a higher orbit r(2), to do this it must fire it's engines, i.e. accelerate the craft (a) for some time (t), and presumably increase its velocity as ?v = at, however Newtonian theory tells us that the velocity has indeed decreased as r(2) is larger than r(1).
So I would like to know what kind of Hokus Pokus is normally applied to explain this problem.
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" The root of the problem, I believe, is that astronomers are using spectral doppler shift to measure rotation of the galactic disk, and then making a false assumption that this velocity is positive. "
I do not think that there is such an assumption - the velocity field can be measured across the plane of the viewed galaxy (if it is somewhat inclined to the line of sight).
Viz:
figure reproduced in:
Note figure 1 in that second link.
Half the plots (roughly) show negative-going plateaux, half positive.
As one might expect from viewing randomly arranged rotating bodies.
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For example:
In astrophysics, in the theory of black holes, when it is said that an in-falling body will appear to “freeze” (stop) at an event horizon of a black hole (originally by Oppenheimer & Snyder) there is a misconception: The radiation from such an object will have already fallen far below the visible spectrum of an observer stationed at a safe distance from the horizon, and the quantity of radiation emitted will approach zero as wavelengths approach infinity. What will be seen of a falling object still relatively high above the horizon is a fading and flickering – then nothing. And to be clear, so long as an object is visible, its acceleration will be observed to increase (it is falling in an intense gravitational field!) as its clock and emissions slow.
See my Black Hole Physics.pdf
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The mistake of James is to not grasp that GR equations are local, which translates to differential equations constraining locally space-time. The local constraints are the ones of special relativity including the local speed of light constancy, the differentiabiliy (smoothness) of space-time, and the principle of equivalence assuming that the local laws of physics are the same locally in any free-falling frame.
So tiny objects crossing the black-hole horizon are not subject to any other local rules than other free-falling objects. Tidal stress is a second order effect that vanishes in the limit of the object zero size.
When one solves the GR differential equations given boundary conditions, one finds the relationships between distant observers. All over the solved domain GR local constraints apply. It is then illogical to assume that the local rules of GR apply, and with given reasonable boundary conditions (flat asymptotic space-time, spherical geometry) that the non-local solutions are wrong.
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What are the observational and practical evidences to support the fact that there exist strongly correlated astrophysical fluids in galaxies?
Suggested reading materials are welcome.
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Look at any maps of the Milky Way in various wavelengths (radio, infrared, x-rays, ...) and you will see correlated structures, such as clumps, filaments, shells. All these structures can be understood as "fluids" in the sense that they follow conservation laws, and the mean free-paths of its ions, atoms, molecules, grains, ... is much shorter than the larger scale structure. In the extreme dense direction you find stars that are of course also fluid and correlated structures. In the large scale direction galaxies are composed of a special fluid where the particles are stars, where their mean-free path is much larger than the galaxy itself, but nonetheless form a so-called collisionless fluid. Some plasmas also are in this collisionless regime where ions are channelled by magnetic fields.
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This post, written by Thomas Boisson for the group Astrophysics, Astronomy, Quantum Physics on Facebook, summarizes all the major problems of quantum physics, nuclear physics, cosmology, particule physics and astrophysics that are still to be solved.
You can propose your solutions, ideas, for each of the mentioned problems. The goal is to make this discussion a rigorous scientific debate.
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Search to measure mental construct
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Hi All!! I have recently completed my PhD in theoretical astrophysics with work on accretion flow around black holes. Now I want to venture into some observational studies. I would like to know how I can make use of the VIRTUAL OBSERVATORIES to start some good quality research work in observations. I would be very glad if you could share some useful links or documents. Thanking you all...
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A Virtual observatory provides user a virtual platform to get access to astronomical large data base, user friendly softwares for processing and analyzing the data. The Virtual Observatory India project (http://voi.iucaa.in/voi/abouVOI.htm) is one such platform. Link to other virtual observatory sites can be found at http://voi.iucaa.in/voi/linkstosites.htm.
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Astrophysical objects stability in their own state.
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Neutron stars and white dwarfs are stable because of the Pauli exclusion principle that quantum-mechanically prevents further gravitational collapse. Black holes are not stable because they continually accrete infalling material while the event horizon keeps material, including light, effectively in orbit about the black hole's "center".
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Spherical waves are ubiquitous in astrophysical environments. Can someone provide some useful references on spherical wave analysis in spherical gravito-magnetized fluids?
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J. P. Cox, Theory of Stellar Oscillations, is a good place to start. It's a little old but thorough in theory and observations. Additional references are difficult to provide without knowing your application. Cox is good for stars, but other systems have different approaches.
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Normally, people apply plane-wave analyses even in a curved geometry, often irrespective of wavelengths. It is mostly encountered in the area of astrophysics and space sciences, even without considering any inter-dependency between the perturbation wavelength and the radius of curvature. What is the main justification?
Can I get some references on the planar-nonplanar wave connectivity and inter-transitional behaviour?
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I am grateful to you all for answers and references.
Hope this discussion to continue.
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I will be very grateful if anyone can give the examples for both in astrophysical and laboratory perspectives.
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Such a thing as a stable chargeless massive elementary particle does not exist in plasma or otherwise.
The lowest stable complex massive particle "that seems" to be chargeless is the neutron, but its internal structure is in reality made of 3 elementary charged particles whose sum of charges adds up to zero, which iswhat makes the neutron appear chargeless.
This is true from both astrophysical and laboratory perspectives.
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I wonder about the source of the formula at internet
[((z+1)2-1) / ((z+1)2+1)] c / H0
H0 – Hubble’s constant, c – speed of light.
Comparing Hubble calculated distances and brightnesses with Pan Theory calculations of distances and brightnesses."
I have checked the formula against 100 galaxies with [0<z<=1]. The correlation was ca. 99%. Somebody knows where the formula stems from? JM
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Once again, as JPG image
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It is well-known that the ground velocity of a plane or helicopter does not depend on relatively fast Earth rotation (~2000 km/h). But a rocket's ground velocity at the high enough altitudes does it increasing if the flying direction is close to the direction of rotation and vice versa.
What is the dependence of such a shifting on altitude?
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Thierry,
You are wrong. Coriolis and centrifugal forces are named fictitious because they don't exist in a proper inertial frame. If you need to check, look what happens in a rotating vacuum chamber, you will see air is not necessary
for Coriolis force to act.
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-Up to now we usually use the classical mathematics the origin of which is at the end of the 19th century and/or at the beginning of the 20th century. Even the contemporary quantum physics, astrophysics, and AI of the 21st century are still using that classical mathematics! In von Neumann's quantum mathematics there is no any anomaly whatsoever in Thomas Kuhn's 'The Structure of Scientific Revolutions': why?
-Thanks for your answers! Marc
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Dear Marc ~
When I think of the mathematics of “classical” physics (hydrodynamics, properties of materials, Maxwell’s electromagnetism, Einstein’s gravitational theory, etc) I see that it is predominantly based on the concept of continuity. Space and time are thought of as continuous variables and physical phenomena are desribed by continuous “fields”. The appropriate mathematical tools are differential equations. “Discreteness” rather than continuity entered physics with Planck’s “quantum” concept, which led to the “non-classical” physics of quantum theory. By analogy, I would identify “classical” mathematics as the mathematics of continuity; "non-classical" mathematics would then be the mathematical study of discrete structures. But those branches of mathematics already exist, so I admit to being rather puzzled by the question "Where is the 'non-classical mathematics'?"
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Hawking's Legacy
Black hole thermodynamics and the Zeroth Law [1,2].
(a) black hole temperature: TH = hc3/16π2GkM
The LHS is intensive but the RHS is not intensive; therefore a violation of thermodynamics [1,2].
(b) black hole entropy: S = πkc3A/2hG
The LHS is extensive but the RHS is neither intensive nor extensive; therefore a violation of thermodynamics [1,2].
(c) Black holes do not exist [1-3].
Hawking leaves nothing of value to science.
REFERENCES
[1] Robitaille, P.-M., Hawking Radiation: A Violation of the Zeroth Law of Thermodynamics, American Physical Society (ABSTRACT), March, 2018, http://meetings.aps.org/Meeting/NES18/Session/D01.3
[2] Robitaille, P.-M., Hawking Radiation: A Violation of the Zeroth Law of Thermodynamics, American Physical Society (SLIDE PRESENTATION), March, 2018, http://vixra.org/pdf/1803.0264v1.pdf
[3] Crothers, S.J., A Critical Analysis of LIGO's Recent Detection of Gravitational Waves Caused by Merging Black Holes, Hadronic Journal, n.3, Vol. 39, 2016, pp.271-302, http://vixra.org/pdf/1603.0127v5.pdf
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Well, to put it on a more concrete foundation, here's my view on his scientific achievement, not exhaustive, as I don't think I am entitled to judge on Hawking's scientific legacy.
His works on black hole theory are from about 50 years ago, and I would consider the singularity theorems he proved together with Roger Penrose quite the highlight of his scientific career. In a nutshell, what they say is that black hole creation takes place under very general conditions in space-time and is a necessary consequence of ART, and does not require very special, e.g. highly symmetric conditions.
With his work on Hawking radiation from teh mid-70s he applied semiclassical analysis to ART which paved the way to a more thorough treatment of quantum field theory on curved space/spacetime.
Although his scientific highlights might stem back from the 60s and 70s, I would nevertheless stress that his legacy surely comprises all that he did as an ambassador to science, as it seems. He surely was someone who gave inspiration to at least a complete generation of scientists many man years ago, his publicity starting to spread with the little booklet he wrote end of the 80s: "A Brief History of Time". I would never underestimate the importance of lighthouse figures like him with this regards, even though the hard-core scientific hightime had then already been past.
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Dear all,
In the framework of a special issue of a French magazine that I am co-directing, I am looking for researchers working on Africa in different research fields, for short interviews about the future of Africa.
Women and African researchers are highly welcomed to apply for a better representativity of genders and countries.
Targeted fields, about Africa only (this list in non exhaustive):
- literature/linguistics
- physics/astrophysics
- terrestrial/marine biology
Thank you for your suggestions and applications,
Julie Morin-Rivat, PhD
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Hi Leonor. How are you doing. I want to recommend Dr. Joana Bezerra, she is doing a very interesting work in South Africa with land use and tradicional populations bezerra.joana@gmail.com
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This project aims to determine laser frequency on-board a Spacecraft. The Spacecraft will be launched with a Space Qualified Stabilized laser device as a payload. When the Spacecraft goes beyond the ‘Sphere of Gravitational influence’ of the Earth (having approximately a radius of 1,500,000 ?km), the laser device will be operated remotely, so as to determine its frequency during the later part of its journey.
We would like to get some advice about recommended type/model of a miniaturized/ compact Space Qualified Stabilized laser device that will be a good choice as cost and weight are the limiting factors for a cost-effective Space experiment.
The miniaturized/ compact Space Qualified Stabilized laser device will be like those developed by Prof. Robert L. Byer of Stanford University. What will be the most suitable type/model among those presently available from manufacturers, and that are at present being utilized by Principal investigators (PI) for similar Space experiments.
The recent findings in terrestrial laboratories (viz., the PTB Lab. at Braunschweig, Germany, the European Laboratory for Nonlinear Spectroscopy {LENS}, in Firenze, the Italian standards Lab. in Torino, the NIST Lab. at Boulder, Colorado, USA, and the Quantum Metrology Lab., RIKEN, Japan), indicate that the differences of the frequency shifts of a particular type of clock/ laser between labs are in ~10's of Hz, while the current laser/ clock measurement precisions are in the milliHz domain; whereas, the frequency shifts due to the strong solar gravitational potential are of the order of MHz.
Takano T., et al, (Referenced below) have reported measurements (having precisions in the milliHz domain) of fractional frequency shifts between two laser (87Sr) clocks located at two terrestrial laboratories.
Whereas, the proposed Space experiment can be conducted utilizing any Space Qualified Stabilized laser/ clock having even lower measurement precisions than the ones belonging to milliHz domain.
However, the final choice of chosen model of the Laser device will depend on the availability of such Space Qualified Stabilized laser devices and also on cost considerations.
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Some answers to this question, obtained so far, has been and will be presented in the “Project Updates” section (Update 3 and beyond).
K.R.S. Mani
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Why does the emission wavelength directly proportional to its duration?
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Solar flares and type II radio bursts have different origins and thus their durations should not be similar. It is believed that solar flares are caused by release of energy and plasma heating/acceleration due to sudden disruption of magnetic structures of parent active regions. Type II bursts are related to shock waves which can be generated in the low corona and can propagate far away in the interplanetary medium that can lasts dozens of hours. Life time of shock waves is, in general, independent of duration of an accompanying flare, even in the case when a flare is a driver of a shock wave (the case of a blast wave). In such case, a flare just generate a blast shock impulsively, and the shock is propagating freely after that. There is another case, when a shock is driven by a coronal mass ejection (the case of a piston shock). In such case, the shock wave and an associated type II burst is not dependant on an accompanying flare at all.
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I would like to change the preference of my research interests. How do I achieve that?
I am interested in astrophysics and astronomy
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If you go to your profile page (click your photo at the top right) then "Research Interests" is right hand tab on the list just under the main heading.
It seems to be created automatically from threads you follow or where you have clicked the "recommend" button so I don't think you can change it. There's an (i) pop-up that says:
  • "This is where you can see all the work you have followed or recommended. Simply click follow on a publication, question, or project and it'll be added here for you to come back to later."
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Dear All,
not only in our university, but almost in all well known to me lectures about Dark Matter, MACHOs (Massive Astrophysical Compact Halo Objects) are rather incidentally discussed while candidates as WIMPs, Axions or Sterile Neutrinos dominate the talks.
Is this - with nowadays knowledge and theoretical assumptions - justified?
With the description of a great abundance of primordial black holes MACHOs do serve a hypothetical answer for almost any questions like rotation curves, radial velocitiy, intermediate black holes, missing-satellite-problem, too-big-to-fail-problem, ...
Of course it is a highly speculative topic. BUT the WIMPs are too (if not even more). So shouldn't we - in accordance with the Principle of Occam's razor - favor MACHOs instead, because they are able to solve a lot of problems at once and at the same time we don't need to extend the Standard Model for introducing them?
Why do WIMPs and particle-like entities dominate? Did i miss a hint (for example some fundamental advantages of this models?). Or is it a general problem ultimately based on ignorance to a great extent?
Thank you
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The best way to assess the possibility would be to start by surveying the observational evidence for dark matter and consider what fits all the resulting constraints. For example how would MACHOs as dark matter explain the evidence from primordial deuterium abundance?
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May be, just this problem is the central problem for cosmology and cosmologists.
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I would not say that this is "the central problem for cosmology and cosmologists". Cosmology does not deal with events on the level of a single planet.
Mason's answer addresses human-induced extinctions, which are certainly already happening. Such repercussions of our behaviour could be termed "the central problem for humanity".
"Extinctions aren't one hit and over with" - well, sometimes they are. Natural events can cause both slow and fast mass extinctions. The Permo-Triassic was an example of "slow" - it took around 60,000 years and is firmly attributed to prolonged volcanic emissions at the Siberian Traps. On an intermediate timescale, the approx 10 km wide asteroid strike which led to the extinction of the dinosaurs (and much else) was a sudden event, but the full ecological impact took time to work out - probably a few hundred to a few thousand years.
However, hit a planet with a large enough asteroid and you get a "fast" extinction: a 1000 km wide impactor causes almost instant global sterilization. Earth suffered a few such hits in the Hadean Eon. But it is unknown whether life managed to become established prior to or in between these events.
Which brings us back to the original questions: "When might the next natural extinction be expected, what events testify its approach, and what measures should humanity take to minimize its harm?" As far as asteroid strikes go, all the large "sterilization level/planet-killer" ones are accounted for, at safe orbital distances from Earth. Once you know the existence of an asteroid and have tracked its orbit, you can determine whether it is on a collision course at some future date, or even whether a future dynamical interaction with another substantial body might divert it towards us. We are increasingly taking measures to survey the night sky for smaller, as yet undiscovered near-Earth objects (NEOs). So it would not be possible for a "dinosaur-killer" sized body to sneak up on us.? "City-killer" sized objects (10 - 100 m) are a real threat, due to their number and difficulty of detection; the 2014 Chelyabinsk object hit us without warning on the sun-facing side of Earth, as did the 1908 Tunguska event. But thankfully such things are much smaller than an extinction-inducing event.
There are other candidates for astronomical mechanisms which could be responsible for mass extinctions. The ionizing blast of gamma rays and cosmic rays from a sufficiently proximate Gamma Ray Burst (GRB) or supernova could do it, although none are conclusively identified with historical extinctions. There are no progenitors for such an event close to us now or in the coming few million years.
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Suppose there is a spherical mass that is *almost* a black hole. It should be possible to measure the distance from the center of the sphere out to an imaginary spherical surface a long distance R away from the center. If we measured the surface area of that imaginary sphere, would it equal 4*pi*R^2?
I have a follow-up question, based on the answer.
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The proper distance d(r) up to the the radial coordinate r and the proper surface area A(r) of the surface at fixed r around a spherically symmetric mass (like a small spherical star) are obtained using the Schwarzschild metric. While d(r) is given by the integral of ?1/sqrt(1-2GM/c^2 r) over the limits ?0 to r, the area A(r) is simply 4 pi r^2. Physically the relation between d(r) and A(r) can be measured by estimating how the bolometric flux of the radiation from the star falls off with the physical distance d(r) given a fixed bolometric luminosity of the star.?
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Cosmologist are puzzled by the small value of the cosmological constant. Why don't they accept my non-singular model of the universe based on the back-reaction of quantum fields.?
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Dark matter is still a mystery. It can have unknown type of self interaction apart from gravity. Such interactions influence shape of dark matter halo. Conversely, by studying shape of dark matter halo one can try to guess a form of self interaction.
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For example, our sun being at close proximity the separation of photons (separation of colours) is too small to detect, but distant systems such as the recently discovered self-lensing binary system KOI-3278, which was discovered by Ethan Kruse and Eric Agol of Washington University, may provide an opportunity to test QGD’s prediction of gravitational colour separation. By the time the light from such a distant system arrives to Earth, the effect should be magnified so as to make the colour separation measurable using high resolution detectors.
Could this explain the spectral lag observed below:
Would it look like this:
See the section on "bending of light" in the attach document.
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Concerning the frequency dependence of light deflection: we have (rather rough) measurements at light frequencies, which show that GRT is valid, maybe to 5-10% error (the classical light deflection in eclipses). On the other hand, we also have radio frequency measurements, which show that the same theory, GRT, is valid at a precision of 10^(-5). So the deflections at optical and radio frequencies are within 5-10% of each other. Since the radio frequencies were at some tens of GHz, and since optical frequencies are at some hundreds of THz, one sees that changing the frequency by a factor of 10'000 has only a marginal effect, if at all, on deflection.
So QGD seems to have a slight problem. Not, I suppose, that that will stop its proponents from ignoring mere facts.
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hallo,
lets assume, intelligent life on exoplanets is connected with a variety of factors which must be given on this planet:
- right Star Class (e.g. G)
- planet formation
- right rotation speed (to?minimize thermal stress?on biology)
- planet with magnetic field to protect the planet
- occurance of water (origin: e.g. comets)
- temperature zone, comparable to the earth (e.g. water is liquid...)
- oxygen
- biological cell development
- formation of "higher" living organism
- formation of intelligent organisms
- formation if creative organisms
- lots of others imaginable.
I consider 10 independent factors and each factor has a probability of 10^-3 to occur. Then the result is 1 out of 10^30 planets has human-life.
The visible mass of the universe ia 10^53 kg. The mass of the earth is 6*10^24 kg.? The total visible mass of the universe matches 10^29 times the mass of the earth.
Conclusion: if the entire mass of the Universe would be planets, then statistically another earth would be present (unfortunately there is no mass left over to form suns).
Is this reasonable?
Regards
Lothar
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LS: Is this reasonable?
I'm sorry but I don't think so, let me explain why.
A number of missions have looked for exo-planets, notably Kepler, and to date we know of several thousand. Of those, a few are of the right mass and in or close to the "habitable zone". From observation then, a rough guide would be that the fraction of star systems with habitable-zone planets is 10-4 to 10-3.
Based on the frequency with planets are seen in transit and the probability of transits based on random inclination of the plane of the orbits, it appears that almost every star system (excluding most binaries) has a system of planets.
There are approximately 300 billion stars in the Milky Way. That implies approximately 108 habitable planets in our galaxy alone.
Though less well proven, current opinion on life getting started are that it is probably ubiquitous, where it is possible, it will occur.
The history of our planet showed a long phase limited to single-celled organisms followed by millions of years and millions of species, none of which developed the type of intelligence. It therefore would be fair to guess that there are tens or hundreds of millions of "pond slime planets" and a similar order of magnitude of "jurassic park planets".
The great unknown is what proportion of species evolve intelligence and I don't see that we have any way of estimating that at all. We don't even understand the origin of our own abilities.
Regarding your specific points:
- right Star Class (e.g. G)
Not required, a planet close to a red dwarf may be in the habitable zone and the star would have a much greater stable lifetime increasing the chances of life developing.
- planet formation
Observed to be ~100%
- right rotation speed (to?minimize thermal stress?on biology)
Not required, even a tidally locked planet would have a hot side and a cold side with a "temperate" zone close to the terminator. Flows between the sides would guarantee circulation of energy and nutrients.
- planet with magnetic field to protect the planet
Not required for deep ocean life.
- occurance of water (origin: e.g. comets)
Probably ubiquitous but methane lake life may not be ruled out.
- temperature zone, comparable to the earth (e.g. water is liquid...)
See the current estimates above.
- oxygen
Not required. Life on Earth initially thrived in a reducing atmosphere, oxygen was a poison.
- biological cell development
"Life" need not follow Earth parallels. Forms of viral life may exist that aren't in cellular form.
- formation of "higher" living organism
That is not required for "life" to exist, perhaps you should clarify your question, and that also applies to the subsequent aspects you list.
JG: Clearly, the evidence (or the absence of evidence) points to the smaller numbers.
"Absence of evidence is not evidence of absence." Consider the Prime Directive from the Star Trek series ;-)
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The goal of this question was for e to provide a proof that the Absolute Peak Luminosity of type 1A Supernovae have a G^(-3) dependence.
The argument is correct but it seems to be too?complex.
There is a simpler argument that people can understand better. ?Just follow these links.
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Supernovae distances are mapped to the Absolute Peak Luminosity of their light profiles. This means the the only two measured values are luminosity at the peak and and 15 days later (to measure width).
Supernova explodes through a nuclear chain reaction:
1) C+C->Mg
2) Mg+O->Ca
3) Ca+O->Ni
4) Ni->Co->Fe?
Luminosity is equal to the number of Ni atoms decay per second or dNidt.
So the peak Luminosity is the Peak dNidt.?
There are TWO considerations that together?support my approximation:
a) The detonation process accelerates 2-3 reactions (in comparison with equilibrium rates prior to detonation).
b) The detonation process adds a delay to photon diffusion. The shock wave originated in the core will travel to the surface. When the shock wave arrives at the surface, reaction 1-3 should (in principle) stop. Ejecta (non burned residues) are then eject and the photons resulting from the Ni decay have to diffuse through the thick ejecta cloud.
If you look into the Light/[C]^2 curve, you will realize that is has a small delay with respect to Light curve. ?The constraint of having a finite star size forces the maximum absolute peak luminosity to synchronize itself with the maximum peak Magnesium rate dMgdt, which happens at the maximum radius. So, the Physics of a finite star and a shockwave nuclear chemistry process forces the Peak Absolute Luminosity (dNidt) to match the maximum rate of Magnesium formation (dMgdt). Implicit in this conclusion is the idea that the pressure and temperature jump expedites intermediate fusions.
My contention is:
a) Light has to go through a diffusion process while traveling from the core. The motion of the detonation curve might synchronize light and [C]^2
b) The model in the python script?contains a parameter associated with the light diffusional process leading to the peak luminosity.
I would love to hear about the chosen rate values (I used arbitrary values that would provide a time profile in the order of the observed ones). I would appreciate if you had better values or a model for rewriting the equations for the nuclear chain reaction.
I see the detonation process as a Mg shock wave propagating?through the star. Light would follow that layer and thus be automatically synchronized with [C]^2
Under these circumstances, volumetric nuclear chemistry depicted in the python script would have to be replaced by shockwave chemistry. ?That would certainly be only dependent upon the Mg content on the shockwave and thus make light be directly proportional to [C]^2!!!
In Summary:
HU see the Supernova Light process to be proportional to [C]^2. ?This assertion has support on two mechanisms:
  1. Detonation temperature increase will increase the rate of equations 2-3
  2. Detonation process should be modeled as a nuclear chemistry shockwave where Mg is being consumed as fast as it is being created. Light is following this shockwave and will peak by the time the shockwave reaches the surface of the Star. ?So, the shockwave mechanism ties together light diffusion and Carbon nuclear chemistry.
Since I wrote this, I followed up on my own suggestion and considered the shockwave nuclear chemistry approach. You can download all my scripts at the github below.
The shockwave model considers that the amount of light on a cell along the shockwave is is the integrated light created through its?evolution. It is developed as a unidimensional process since the observation (billions of years away from the supernova) can be construed as having only contributions from all the cells along the radial line connecting us to the Supernova.
So, the model is unidimensional. That said, it contains all the physics of a tri-dimensional simple model. All rates are effective rates since during the Supernova explosion nuclear reactions are abundant (one can have tremendous variations on neutron content).
The physics is the following:
a) White Dwarf reaches epoch-dependent Chandrasekhar mass. Compression triggers Carbon detonation A shockwave starts at the center of the White Dwarf
b) That shockwave induces 2C->Mg step. The energy released increases local temperature and drive second and third equation to the formation of Ni. ?Ni decay releases photons.
c) Photons follow the shockwave and diffuse to the surface where we can detect them. The shockwave takes tc to reach the Chandrasekhar radius (surface of the White Dwarf).
d) Luminosity comes from the Ni decay from the element of volume plus the aggregate photons traveling with the shockwave. They diffuse to the surface
e) Two diffusion rates are considered. One for light diffusion within the Star and another for diffusion in the ejecta.
# Diffusion process with two rates 0.3 for radiation created before the shockwave
# reaches surface and 0.03 for radiation diffusion across ejecta
kdiff=0.3*(t<tc)-0.03*(t>tc)
f) I considered tc to be 15 days, that is, it takes 15 days for peak luminosity. Changing this value doesn't change the picture.
g) The peak luminosity is matched to the peak Magnesium formation at t=tc or when the shockwave reaches the Star surface.
This means that Physics makes the Absolute Luminosity Peak to be also the peak of Magnesium formation and that takes place at the Star surface.
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Researchgate doesn't allow for deletion of a question, so I will just replicate a derivation of Luminosity proportional to G^(-3).
Dr. David Arnett was generous to point out that he didn't agree with my argument using the thermonuclear chain reactions. ?It is not clear that he disagreed with the final conclusion.
In any event, Dr. Arnett made an imprint on me. ?Like a duckling recently hashed, Dr. Arnett's work was the first one I found modeling Luminosity. ?So, he is like a (duckling) mother to me...:)
If, my idea were to be correct, it would probably have to be correct within the logical framework created by Dr Arnett's oeuvre.
So, I searched his work for equations of Luminosity of Supernovae. ?Found one from 1980. I started with equation (40) and revied what influence a variable G would have on it. Since the radius of this Supernova varies according to Chandrasekhar radius or G^(-1/2), and since epoch-dependent Supernovae are scaled down Supernovae, their thermal energy (a volumetric integral) would scaled with G^(-3/2)... Left was the calculation of the mass of the Sun within that context.
I understood as Mass of the Sun, not as the mass of our current Star Sun, but as a unit of mass (currently matching the Sun's mass) but in the context of a Supernova.
The context of a Supernova means that radiative pressure outweighs?gas pressure. ?In that regimen, all the Gravitational dependence of the Sun's mass is included in its mass.
L (Sun) is proportional to Sun's mass.
The Luminosity of the star is also directly proportional to its surface area. That bring about another G(-1). The last G(-1/2) comes directly from a R factor. ?So:
Thermal energy scales with G(-3/2)
Sun Mass has a dependence ?of G^(-1)
Radius scales with G^(-1/2).
The total dependence of the Supernova Luminosity is the product of all these dependences or G^(-3).
So, I obtained the same result from my simple-minded physical reasoning using the infinitely more sophisticated work of Dr. David Arnett.
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what are measured Stark broadening parameters for Mn I = 460.53 nm and Fe I 413.46 nm?
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It depends.
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I have observed rotation curve data of a galaxy, and I?want to know what is the best and simplest mathematical model to find the galactic rotation curve and dynamical mass of such galaxy.?
Your help will be appreciated
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?Dear Thierry De Mees,
I have downloaded your book "Gravitomagnetism/Coriolis Gravity Theory" and will spend my winter break reading through it. As I recall, in the past, Voyager images lead researchers towards the Coriolis effect as an explanation for the Great Red Spot on Jupiter. Thank you.
Sincerely,?
Terry R. Fisher
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Pioneer-V was 5.2 x 10^6 km (or 863Re) on Sun-Earth line on March 31, 1960, when first engulfed by solar plasma, but the peak of the interplanetary magnetic field (IMF) was only measured six hours later, after it was measured by Honolulu station. This study shows the IMF was produced 12.5 RE from the earth, but the question is where the IMF was produced? (Given by one page of section “2.1 Re-Visiting the Historical Experiment” with related Fig.1 at: http://www.exmfpropulsions.com/New_Physics/SpacePhysics/Solar_or_Interplanetary_External_Magnetic_Field.pdf)
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Thanks Ram.?
In our article “The Source of the Interplanetary Magnetic Field (IMF) Measured by Pioneer V,” we showed several contraventions between the extra wonderful experiment carried at 5.2 million kilometers on sunwards, on March 30, 1960. During the first 55 minuets, while engulfed with the solar plasma, the probe didn’t measured any increase in magnetic field, and if it’s embedded within Solar wind, this should have been measured right from the first arrival of the protons.
That failure forced the experimenters to endorsed the only know option, as they stated: “The only known way by which these transient fields could be established, or existing fields manipulated is by moving, conducting plasma of solar flare origin,” but arguments given in the paper Showed a great mistake was done, and upon which the current hydromagnetic is based. This paper explain what took place on?
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The Interplanetary Magnetic Field (IMF) as of solar origin was endorsed mainly due to the final report of the Pioneer V experiment on March 30-31, 1960. After reading point 3 in the poster you can decide for yourself (3. Weak Points in Pioneer-V Results Interpretation).
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In our article “The Source of the Interplanetary Magnetic Field (IMF) Measured by Pioneer V,” we showed several contraventions between the extra wonderful experiment carried at 5.2 million kilometers on sunwards. During the first 55 minuets, while engulfed with the solar plasma, the probe didn’t measured any increase in magnetic field, and if it’s embedded within Solar wind, this should have been measured right from the first arrival of the protons.
That failure forced the experimenters to endorsed the only know option, as they stated: “The only known way by which these transient fields could be established, or existing fields manipulated is by moving, conducting plasma of solar flare origin,” but arguments given in the paper Showed a great mistake was done, and upon which the current hydromagnetic is based.?More at:? “The Source of the Interplanetary Magnetic Field (IMF) Measured by Pioneer V,”at: http://www.omicsgroup.org/journals/the-source-of-the-interplanetary-magnetic-field-imf-measured-by-pioneer-v-2329-6542.1000108.php?aid=29838
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Hi, dear American cowboys! Has anyone tested the secondary aberration effect (i.e. v^2/c^2) at the conventional group delay model with geodetic VLBI?
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The term v^2/c^2 also?causes the length contraction, and in the case of VLBI this term?contracts the VLBI scaling factor (the Earth radius). My quick test shows that the actual contraction is a bit larger than predicted by the theory (~5%).
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Is there a chance for cryo-pycnonuclear reactions to take place in the degenerate core of a white dwarf, affecting this way its stability?
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degenerate matter cannot quench nuclear reactions with pressure responses the way normal matter can since degeneracy pressure doesn't depend on temperature (not strongly anyway). so if any reactions were to occur inside a WD, they?would rapidly lead to a runaway nuclear catastrophe. and as william pointed out, that would no longer be a WD.
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How can answer my kid 5 years old who asked me (who is On/Off the moon night and morning?
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Maybe you can simulate the relationship between sun, moon and earth with two ball and a light
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Observations of spectral lines of metal, helium and hydrogen in solar flares and prominences show that their profiles contain narrow emission component which corresponds to the very strong magnetic fields (10 3 - 10 4 G) and very low temperatures, approximately an order of magnitude lower than that outside the regions of strong fields (see. eg. Lozitsky V.G. Advances in Space Research, 2015, 55, 958; Lozitsky V.G. et al., Kinematics and Physics of Celestial Bodies., Suppl., 2000, No 3, 449). Because of the limited spectral resolution of observations, the exact value of the lower limit of temperature and the turbulent velocity remains unknown. And what says about this the theory?
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please have a look at
Magnetohydrodynamics — Historical Evolution and Trends
S. Molokov, R. Moreau and H. K. Moffatt, Eds.
(Berlin: Springer 2007) pp. 85–115 [E-print: astro-ph/0507686]
for more details
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If we imagine the Universe as a 3D space-like surface of curved sphere in 4D space, how big is then the radius of this 4D sphere?
The Visible Universe can be in such a picture imagined as just (3D) circle on the surface of this 4D sphere of said above radius. Its diameter is assess on: "An approximate diameter (in metres) of the visible universe (93 billion light years): 8.8 × 10^26." http://www.physicsoftheuniverse.com/numbers.html
despite of the fact that it accounts ca. 14 billion years... ?All that due to rapid expansion of this 4D sphere. Are there any guesses on this sphere radius?
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ZM: If we imagine the Universe as a 3D space-like surface of curved sphere in 4D space, how big is then the radius of this 4D sphere? ... Are there any guesses on this sphere radius?
There are limitations to what we can compute for this, some of which I'm looking in to, so this is not so much a guess as a pointer to what needs to be considered to make a guess.
As Louis said, the universe may be spatially infinite so the question only makes sense if we first assume that it is finite. In that case we could estimate the minimum size based on the measured curvature of the observable portion.
[edit] The radius is R=c/(H0√ΩK). The Planck mission 2015 results set says ΩK is 0.0±0.005 so a rough guess might be that the circumference of 2πR is at least 88 times the Hubble length so about 1300 billion light years. [\edit]
Incidentally, I'm not sure that considering the radius is valid as it would be orthogonal to all the 3 dimensions of our space, circumference is more meaningful as it would be the proper distance in the 3D to get back to your starting point.
However, there is a fundamental problem, the curvature of the observable universe may not be representative of the whole, it is a small volume sampled for the much larger total and we might expect that to give a Gaussian distribution of measurements if we could measure multiple sufficiently separated samples.
I wonder whether it might be possible to estimate the width of that distribution from the Harrison-Zel'dovich spectrum with Planck's measured spectral index of 0.96, but that's where my maths reaches its limit.
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If spacetime is like a liquid—a concept some physicists say could help resolve a confounding disagreement between two dominant theories in physics—it must be a very special liquid indeed. A recent study compared astrophysical observations with predictions based on the notion of fluid spacetime, and found the idea only works if spacetime is incredibly smooth and freely flowing—in other words, a superfluid.
If it is true that spacetime is a superfluid and that photons of different energies travel at different speeds or dissipate over time, that means relativity does not hold in all situations. One of the main tenets of relativity, the Lorentz invariance, states that the speed of light is unchanging, regardless of an observer’s frame of reference. “The possibility that spacetime as we know it emerges from something that violates relativity is a fairly radical one,” Jacobson says. It does, however, clear a potential pathway toward rectifying some of the problems that arise when trying to combine relativity and quantum mechanics. “Violating relativity would open up the possibility of eliminating infinite quantities that arise in present theory and which seem to some unlikely to be physically correct.”
If spacetime is a superfluid, then what is the role of gravitons?
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Fluids don't propagate transverse wave modes but light is polarised hence must be transverse.
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In my opinion, x-ray photometry works but I'm looking for the best method and other methods.?
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Good find by Eric.
1.64 microns is in?the middle of?the?H band, which has the added advantage of being where most adaptive optics systems are optimised. This would help to pick out smaller, more distant, or?more crowded?SNRs.
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There are several material which light in weight and transparent also they won't allow cosmic radiation to penetrate to it. I'm looking for that kind of material.
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In fact there are hardly any neutrons or gamma rays in primary cosmic rays incident on the top of the atmosphere. However they are produced within the atmosphere in a cascade of secondary particles that include everything known to man and probably many that are not. Primary cosmic rays are mainly energetic protons plus all heavier ions. For these, hydrogen is definitely the best shielding material. Use of fuel and water is proposed for interplanetary travel while polythene is used on the ISS.. If you are considering secondary particles near the earth's surface, these are mainly neutrons and mu-mesons. Hydrogen is again optimum buit in practice concrete and soil are used.
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Hubble's law says that the universe expands.
But the fact that we see other galaxies moving away from us does not imply that we are the center of the universe. In any point of it the picture will be quite similar: The galaxies will have radial velocity of ca.70 km/s/Mpc or 20 km/s/Mly. It does mean that at the distance of 15 Milliard light years (15 Billion in the American system) they reach the speed of light and still will be accelerated with a distance. The latter means also that they will vanish behind the events horizon and, nota bene, their true relative velocities with respect to us will be greater than c.
When it happens many people think that they vanish from our space without a trace, just as ships vanish after curved horizon of a sea.
Let us consider this more closely:
Let us take 0<epsilon<D, where D critical distance in light years (from Solar System) of such "tranzition" behind the events horizon.
In the moment just before "tranzition", at a distance (D - epsilon), they emit light which arrives to us after (D - epsilon) light years.
But after that critical moment of "tranzition", at a distance (D+epsilon), they still emit light (each star emits the same amount of energy as before in a continuous manner).
That light approach us 2epsilon years latter.
Epsilon may be any number of years.
This could mean the following conclusion: We can see? the distant galaxies, even those of them which just "vanished" after the events horizon with velocity c. Moreover, each year we could see more (and not less) of them.
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Well, you already have answered your question. The most distant galaxies which we observe today are "at present" receding much faster than light?emitted by them could catch up. The galaxies beyond the event horizon will remain untraced unless?the Hubble law reverses!
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According to Darwinian Evolution it is accepted that all life on earth has derived from a single source of DNA from which all life has evolved. If extra-terrestrial life has a completely separate source, and unimaginably different attributes, would we be able recognize it as life if we found it.
Dr Carol Cleland from NASA's Astrobiology Institute has pointed out that all 'life on Earth has a common origin,' and all 'terrestrial life represents only a single case'. (Astrobiology Magazine Staffwriter, 2003)
Professor Gerald F. Joyce is widely reported as having formulated NASA's working definition of life, and has stated the definition depends upon life being 'maintained by Darwinian evolution.' However, he has also suggested there may be 'another way,' and that it 'would be a huge breakthrough, if there was some paradigm other than Darwinian evolution that gets you what Darwinian evolution gets you.' (Leslie, 2013)
References:
Astrobiology Magazine Staffwriter (2003) ‘Life’s Working Definition: Does it Work’, Astrobiology Magazine. Available at: http://www.astrobio.net/news-exclusive/lifes-working-definition/ (Accessed: 13 July 2016).
Leslie, M. (2013) Forming a Definition for Life?: Interview with Gerald Joyce, Astrobiology Magazine. Available at: http://www.astrobio.net/interview/forming-a-definition-for-life-interview-with-gerald-joyce/ (Accessed: 23 March 2016).
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This question "Would we recognize extra-terrestrial life if we found it", is seeking (and has had) some very helpful qualitative answers.
On the same subject of 'defining life' I have also asked a question seeking more qualitative answers. It provides a list of things and asks for an intuitive 'yes' or 'no' answers as to whether you intuitively believe they are living.
That question can be found at "Is intuition enough to define living things".
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There is a chance that since the moon's gravity is strongest at that point this will minimize the orbital decay. The satellite could also be placed to periodically pass through the high tide to reduce on orbital decay.
Can my idea work?
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Imtiyaz,
The satellite is very firmly experiencing the pull of Earth's gravity - otherwise it would not travel in a closed path!
Objects aboard the satellite may be weightless, but the whole craft is quite definitely affected by gravity.
If you really were a launch director at NASA in 2013 (as your ResearchGate biography says) you would know this.
Or is that a strange joke that I do not understand?
In our current understanding of atomic physics an electron's behaviour in an atom is not similar in any meaningful way to that of a body in a gravitationally bound orbit around another mass
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When considering general relativity and special relativity, the time for an observer dilates when falling into a black hole. The closer the observer reaches the event horizon, the times dilates more. This means that 1 hour for the observer will be 100000000 years for a person on earth. This should continue and beyond the event horizon, the observer should see the universe without the phenomenon called time (the phenomenon that prevents different?events from happening at once). This means that, for an observer living inside the black hole, the universe doesn't have any beginning or end. Every event in the universe happened simultaneously. The big bang and the possible big crunch occured simultaneously. Aren't?me right?
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If you're going by the maths: that does not follow at all.
The interior of a black hole does not behave at all like the exterior, even very close to the event horizon. It is true that in the interior of a black hole time and space would switch character - this is in fact a mathematical way of explaining how we always end up at the singularity: as time always goes towards the future outside a black hole, space goes towards the singularity inside one. This does mean something weird about time - perhaps one is 'free' in it to a certain extent; but reason:
a) once in the interior of a black hole, you cannot escape, and all you will see is any light that happens falls into it;
b) you will fall into the singularity in finite *proper* time anyway, so your experience of being crushed into a singularity will occur in finite time to you, leaving you unable to see anything in the universe at all (even if you could survive the experience, it is unlikely that any constructed or organic object could), and
c) you may be 'free' in space right now in that you can move in any direction, but it doesn't mean you can go to the far reaches of the universe just because you want to; similarly there is no reason to believe that just because time and space switch character inside a black hole, and you become unstuck in time, it does not follow that you are suddenly free to explore all the reaches of time from within it.
Without exploring the maths closely, I suspect the mistake in your thinking is a classic mistake of relativity: comparing my first paragraph with point 2, it's possible your mistake is confusing *co-ordinate* time (that measured from a particular frame of reference stationary with respect to the 'traveller') with *proper time* (that measured by the 'traveller' themselves.)
(Possibly you have heard of the effect whereby if you observe someone falling into a black hole you would never see them even enter the horizon but from their perspective they would enter the black hole in a finite amount of time? This is due to the same difference, between co-ordinate time and proper time. Near black hole, these things become very different measures!)
(PS - you may hypothesise about black holes, but some advice: I urge you to read the vast amounts of information that is already known about them and learn the mathematical background before making hypotheses - there are scarcely any more counter-intuitive objects in the known universe, but they certainly are not objects about which little is known.)
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This question is directed to observational astrophysicists. I am working on the radiation problem associated with massive star formation. I want to know if the opacity of the gas in molecular does vary with distance from the center of a molecular clouds. I see that in the literature this opacity is assumed to be a constant taking a value of about 20 m^2/kg. I will be happy to get an answer from you!
See attachment!
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opacity is a function of three fundamental physical parameters; density, pressure and chemical composition.
since all these quantities vary along the radial distance then the answer should be yes.
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It was suggested many years ago by Jacob Bekenstein that the rotation parameter of a black hole should be quantized as in usual quantum mechanics: J=n * hbar.
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This would make sense only if this angular momentum, defined at the boundary, where the Kerr metric is asymptotically flat, can be identified with the angular momentum of a quantum system. This system, however, is a quantum system in flat spacetime, so the fact that its angular momentum is that of a Kerr black hole doesn't seem relevant. In fact it's the other way around, cf.?http://arxiv.org/abs/gr-qc/9710076
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Assume that the inner event horizon r_ = m - Sqrt[m^2-a^2] is greater than the Ring singularity radius a. That is, a^2 < (m -?Sqrt[m^2-a^2])^2 which for positive mass leads to imaginary?a. We therefore must have the event horizon inside the Ring, and a < m or J < m^2.?
Note that if we further consider the inner ergosphere radius with respect to the Ring and upon demanding cos^2[theta] positive definite we get at the boundary a restriction on the angular momentum: J =?m Sqrt[2m-cos^2]
This?defines a band for J and M : m Sqrt[2m-1] < J < m Sqrt[2m].
See attached plot?
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I guess the kerr solution reveals a naked singularity in case of a>m. In this case the radius of the inner and outer event horizon r=m-sqrt(m^2-a^2) and r=m+sqrt(m^2-a^2) are imaginary. Thus there will be no event horizons for a>m and one gets the problem with a naked singularity. ?
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The energy-momentum tensor of a black hole, or what curves the Schwarzschild geometry?
H Balasin and H Nachbagauer
Using distributional techniques we calculate the energy-momentum tensor of the Schwarzschild geometry. It turns out to be a well defined tensor distribution concentrated on the r=0 region which is usually excluded from spacetime. This provides a physical interpretation for the curvature of this geometry.
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If it's a question of interpretation, or opinion, ?it doesn't matter. What does matter is that energy and momentum can be consistently defined on the boundary of a spacetime only. Now r=0 is a sort of boundary of the spacetime in question-though the fact that it's a singularity mitigates its convenience for the definition of any quantity, ?since it requires additional conditions, that must be shown to be consistent with the conditions usually imposed. That's what a singularity means.?
Incidentally, this is a link to a version of the paper that is accessible:?http://arxiv.org/abs/gr-qc/9305009 Indeed what the authors do show is how to deal with singular geometries. Opinions don't matter, however, in scientific matters. Content does.
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Red planet: blue sunset
Blue planet:?red sunset
Rayleigh scattering, Mie scattering or other effects, which one is dominant effect?
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In the case of Mars, its more of a local phenomenon; dust particles and not atmospheric composition which dominate scattering in Mars.
Compared to Mars, Earth has a relatively thick atmosphere, so most of the atmospheric scattering occurs when light is incident on?an air molecule, known as Rayleigh scattering. Rayleigh scattering occurs when the object a photon scatters off (the air molecule) is much smaller than the wavelength of the photon. The closer the wavelength is to the size of the molecule, the more likely it is to scatter. This means that red wavelengths (which are the longest in visible spectrum) don’t scatter with air molecules much, while blue wavelengths (which are the shortest) tend to scatter a lot. This is why the sky appears blue, since so much of the blue light is scattered.
When the Sun is low in the sky, it’s light has to travel a long path through the atmosphere to reach you. As the light travels through the atmosphere some of the photons are scattered off the air molecules. When the photons scatter off air molecules, they scatter randomly in all directions, so usually when a photon scatters, most of it?scatters away from your line of sight. Since blue photons scatter much more often than red ones (blue wavelength is shorter and more comparable to the size of atmospheric gas molecules on earth), much of the blue light is scattered away. This leaves red photons to reach your eye. Hence the Sun looks red when low in the sky. When the Sun is overhead, the path it takes to reach you is much shorter, so only a bit of the blue light is scattered. So the Sun looks yellow.
Now,?Mars has a much thinner atmosphere (1% of Earth's), so the amount of Rayleigh scattering is much less. But Mars also has a dry, dusty surface, and a weaker surface gravity, so the atmosphere of Mars is often filled with fine dust particles (if you watched the movie Martian, you can recall it). These particles are larger in size than the main atmospheric gases of Mars's atmosphere, also more comparable in size to the larger wavelengths of visible light, so most of the light is scattered by Mie scattering. On the contrary, Rayleigh scattering due to atmospheric composition dominates in the case of earth. While, for Mars, it is the larger dust particles which play the major role and push the scattering characteristics to the Mie region. One of the main differences between Rayleigh and Mie scattering is that Rayleigh scattering tends to occur in all directions, but Mie scattering varies with scattering angle. Also, good to know that the scattering cross-section in Mie scattering region has oscillatory characteristics. Effectively, what this means is that longer wavelengths (reds) tend to scatter more uniformly, while shorter wavelengths (blues) tend to scatter?at slight angles. This further means that the blue light tends to be deflected less than red light which implies Mars can have a dusty red daytime sky, and a blue sunset.
Mie scattering does occur on Earth as well, but since Mie scattering is less efficient than Rayleigh scattering it’s never strong enough to give us a blue sunset.?It can (rarely) produce a blue moon. It happened more than 100 years ago though; due to the volcanic eruption of Krakatoa in 1883, which sent so much ash into the atmosphere it produced brilliantly red sunsets and visibly blue moons all across the globe for nearly two years. https://en.wikipedia.org/wiki/Blue_moon#Visibly_blue_moon
As a result, the phrase “once in a blue moon” came to mean a rare occurrence.
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Some astrophysicians say that gravitational waves (GW) were created during the inflation?phase of the universe, when the universe was 10-36 second old and expanded billions of billions of billions times.?
I understand this phenomenon was really explosive and created very violent effects, maybe including GW, but thinking that the GW would then propagate somewhere else would suppose that there was a "somewhere". But the universe just expanded, increased in size, but did not grow inside something else. So these GW had nothing to propagate in, and could not reach us now.
Furthermore, if the GW propagate at the speed of light in vacuum, they should be far away from us because our speed is much less that theirs. The only GW we can catch from earth should have been created much earlier than the inflation.
Is this correct?
If yes, one could then infer that the GW were the source of the inflation mechanism and somehow pushed the limits of the universe to make it grow.
Can anyone explain this? Thank you.
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This is a very standard material, available in a number of text books.
Inflationary cosmological model was proposed by Particle Physicist Alan Guth and others in early 1980s. Essentially, at high energies, as particles behave as quantum fields, contribution of a quantum field to the energy density and pressure need not be zero. In the Planck era the lowest energy state of this quantum field might have corresponded to a false vacuum, generating a cosmological constant which is? 10100 times larger than what it is today, and resulting in a super-large repulsive force. Such a repulsive force stretches 3-D space which doubles in volume in every 10-43 seconds. After 85 such doubling (in volume) temperature drops from 1032 K to near absolute zero.?
Ref:
  1. The Inflationary Universe: The Quest for a New Theory of Cosmic Origins, by Alan H. Guth, Perseus Books, 1997?
  2. A. H. Guth, Phys. Rev. D 23, 347 (1981)
  3. A. H. Guth, S.Y. Pi, Phys. Rev. Lett. 49, 1110 (1982)
  4. A. H. Guth, E. J. Weinberg, Nucl. Phys. B212, 321 (1983)
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I wanna fill the missing values in the radiation belt electron flux, but i am stucked by which method I should adapt. So can anyone give me some advice? I tried the Singular Spectrum Analysis method, but the window length parameter M and the grouping factor K are diffcult to set. How to determine the optimal parameters then?
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I suggest the following reading:
Quantitative Prediction of Radiation Belt Electrons at Geostationary Orbit Based on Solar Wind Measurements
Xinlin Li, M. Temerin, D. N. Baker, G. D. Reeves and D. Larson
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In the source frame, the initial black hole masses are 36M and 29M, and the final black hole mass is 62M,with 3M radiated in gravitational wave.
There was no EMF, Electron, Positron, Neutrino and Hardrons ejected at old and new emerging Radial Poles?
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Sandip,
Before Wheeler came up with the term black hole in the late 60s people understood the outcome of gravitational collapse to be a frozen star lacking an event horizon. Such objects are often, though not always, observationally indistingishable as far as astronomers are concerned/ By now black holes have been foisted upon mainstream science, exploiting a gullible public and gullible new generations of scientists. That Einstein, Eddington and Dirac regarded the Schwarzschild metric as physically unattainable has been swept under the carpet - but they were quite right to dismiss black holes on account of infinite time dilation. The more you compress an object, the slower time advances for its constituent matter. If you try to create a black hole in this way, time will halt completely to thwart you, saving the universe from a host of absurd outcomes and paradoxes.
I could list a dozen severe problems that the existence of black holes would create for physics and cosmology but your strongest counter-argument would be that we possess metrics describing stationary black holes, objects that would necessarily have to pre-date the big bang. Appeals to a belief in them by celebrity scientists or the sheer number of papers published on the topic in recent decades are really just a symptom, but they attest to the gigantic scale of the disease.
You may be right that the main reason for the 5 month publishing delay could have been political machinations involving India and China but I think this overlooks the more worrying underlying issue. Alternative models were not considered in that paper (despite curious features in the signals) because black hole research has been driven by the politics of the academic establishment, much more so than by genuine science, for the last 50 years. But I think Einstein will once again triumph, even if his warning concerning black holes is currently being marginalised.
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Astro and Geophyscists
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Consider the orbital dynamics. If you want to make a permanent change to the orbit, you need to apply a short force for some time to put the planet onto an elliptical orbit with perihelion at its current radius and aphelion 1km farther out, then wait about 6 months, then apply a similar force to accelerate the planet into your desired orbit. The change in energy will be half the change in gravitational potential (because of the Virial Theorem).
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The 'standard model' of theoretical physics says the basic forces are transmitted between bodies and detectors by particles or fields, as speeds up to the velocity of light. ?The LIGO gravitational signal is found to be of short duration (light crossing time of the emitter, perhaps) and very close to light speed. .Very likely to be waves on the gravitational field (Einstein) but could still be 'gravitons'.?Black holes can't emit light waves, likewise?they can't emit gravity waves and cannot exert gravitational force on matter outside.? So how do the proponents explain?two black holes pulling on each other, orbiting in the gradually closing binary system?
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Philadelphia, PA
Dear Wallis,
Its seems to me that your question concerns how black holes could radiate. You ask:
Black holes can't emit light waves, likewise they can't emit gravity waves and cannot exert gravitational force on matter outside. So how do the proponents explain two black holes pulling on each other, orbiting in the gradually closing binary system?
---end quotation
The key to the production of gravitational waves is not that massive objects emit gravity waves, but that the acceleration of massive objects does. Black holes, since they constitute massive objects, do curve space-time in their vicinity, however, and other objects follow the lines of curvature. In the LIGO discovery, it is the mutual acceleration of two black holes toward each other, and the consequent loss of angular momentum which is responsible for the emission of gravitational waves.
The oscillation of a charge produces electromagnetic radiation, and? the concept of gravitational radiation is analogous: accelerating masses emit gravitational radiation, though in most cases, and with small masses, this is negligible. Its takes the acceleration of gigantic masses to produce detectable gravitational radiation.
The hypothesis of gravitons does not really belong to the standard model of particle physics --which does not include gravity. Instead it belongs to proposals to extend the standard model to include gravitation. These proposals are much more speculative than the standard model. While gravitational waves were strongly and confidently predicted as a large-scale implication of Einstein's theory of general relativity, the concept of the graviton, as the supposed carrier of the gravitational force, is much more problematic, since this concerns extremely small scale phenomena, at or near the Planck length, and falls into the domain of proposals for theories of quantum gravity. Gravitational waves are an implication of GR, gravitons not.
In any case, if one follows the proposals for gravitons (Freeman Dyson, e.g., has expressed strong doubts that they could ever be detected), then they would arise as the quantum of the gravitational field in correspondence with gravitational waves. It is not that black holes, un-accelerated, or other massive bodies would be though to emit gravitons, instead, like the gravitational waves, they would be emitted by accelerating masses.
The two black holes are supposed to "pull on" each other, simply by following the curved space-time in their mutual vicinity. This is in accord with GR. But as they approach each other and there is a loss of angular momentum, the local curvature is repeatedly perturbed so as to produce the expanding gravitational radiation.
H.G. Callaway
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No, the two statements don't imply any such suggestion.?
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Quasars are believed to be objects ejected from the centers of the Galaxies (or Black holes). Do all of them blow outwards in opposite direction to us in order to agree all of them with such high redshifts ? Note that the motion of galaxies is random! While, even no one Quasar exhibits a blueshift !. Moreover, according to their high redshift all of the Quasars are very distant away. But the universe is isotropic, so our position is not preferred. Hence why we didn`t obsreve any Quasar nearby? According to the isotropy, a distant observer should ?observe the Quasars very distant with respect to him, that is they should be nearby to us!. Contradiction. According to Hubble`s law, if the object is bright then its near by and the distant objects are faint. The Quasars are very bright, why shouldn`t they nearby? Why we just accept one part from Hubble`s law, that is: the high redshift of the Quasar indicates that its distant and ignored the other part, that is: the brightness of the Quasar indicates they are nearby?!!1. Finally, Why our Galaxy and many other nearby Galaxies didn`t eject Quasars from their centers? Why this jop is exclusive for distant Galaxies? Because our Galaxy?and many other nearby Galaxies are inactive, said astronomers. Why they are the inactiv among the active distant Galaxies? False justificatioin.It is clear such Paradigm is not satisfactory and insufficient, it depends on many unjustified reasons , many contradictions and inconsistent. The paradigm must be reconsidered and readjusted
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Quasars occurred throughout the early universe but only while there was a lot of gas around to fall into the central black holes. Most of it has been used up so that's why we don't see them nearby, you have to look far away to see earlier times.
They are complex structures and send jets of material out from the poles of the rotating accretion disc but look different if we are not in that direction.
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I am interested in parametric resonance. An introduction to this phenomenon can be found in Landau's book on classical mechanics. Can anyone point out some good reviews on the phenomenon beyond the textbook level? I am looking for some applications of this phenomenon in astrophysical systems. Any suggestions in this direction are welcome
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References Beyond Text Book Level but may not be in astrophysical systems:
(i)E. Kh. Akhmedov ,hep-ph/9903302
(ii)E. Kh. Akhmedov et al ,Nucl. Phys. B542 (1999)3-30; hep-ph/9808270
(iv)V. Gudkov et al, Phys. Rev.? C83 (2011) 025501
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Estimate the ratio between the temperature scale height h = T(dT/dr)-1 and the mean free path of a hydrogen atom in the atmosphere of a star. Is local thermodynamic equilibrium a valid assumption in the stellar atmosphere? Where does it break down?
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From your question it seems you are asking about the validity of describing the hydrogen in terms of its collisional relaxation.? The first answer is about the radiation field which usually is described in terms ofthe language of? "LTE", but you are asking about the description only of the particles in terms of the mean density rho, momentum density rho v, and the energy density of which the molecular motions are described by temperature T.? You ask if the mfp is < temperature scale height.? RIght?? If so then the mfp is about? 1/(N_H sigma) where sigma is a? bit more than? pi a_o^2, a_0 = Bohr radius.? In nearly all cases? mfp is << scale height so single temperatures are a good description.? For example in the Sun, N_H is maybe 10^17 /cm3, sigma is 10^-16 cm2, and so mfp is 0.1 cm.? The scale height in T is enormous, about 10^8 cm order of magnitude.
If you want to see an example of a breakdown of this for helium,? see C. Jordan (1975) paper in MNRAS or Proc. R. Soc. - I cannot remember which.? There she shows that the mfp of some helium atoms can exceed the very small temperature scale height (a few km) in the low density solar transition region.? This is where number densities N are small which increases mfp a lot.? See also Pietarila & Judge 2004 APJ for a more general discussion of helium in the sun and the solar transition region.
hope this helps.
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Its basic ingredients are fields :?The Standard Model includes a field for each
type of elementary particle;?These particles exhibit a wide variety of masses
that follow no recognizable pattern;?The Standard?Model has no mechanism that would account?for any of these masses, unless we supplement it?by adding additional fields, of a type known as?scalar fields. The word “scalar” means that these?fields do not carry a sense of direction, unlike the?electric and magnetic fields and the other fields?of the Standard Model.
To complete the Standard Model, we need to?confirm the existence of these scalar fields?and find out how many types there are? This is a?matter of discovering new elementary particles,?often called Higgs particles(why ?), that can be recognized as the quanta of these fields.
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Standard model is an SU(3) x SU2)Lx U(1)em invariant gauge theory. This theory is renormalizable and not anomalous. Anomaly free condition means that after quantization of classical fields, the quantized field theory can maintain symmetries of its classical counterpart.
Gauge couplings?αs g and g' are universal, ie they do not differentiate between generations and also they are same for multiplets within each generation. Yukawa part of the standard model Lagrangian has a number of free complex parameters, which are the Yukawa couplings. At present the theory does not have enough predictive power to fix them. They are fixed by experiments. In this sense, the standard model is a phenomenological model.
The Higgs boson used to be a theoretical idea (within standard model) until a few years ago. But now its existence is experimentally established. This discovery has put standard model into a firm theoretical footing.
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A massive O star has a typical luminosity of 3 x 1039?ergs s-1, a lifetime of 3 x 106 yr, a stellar-wind velocity of 5000 km s-1, and a mass- loss rate of 10-5 Ms yr-1. When it ends up as a supernova, ~5 Ms?is ejected with a velocity of 5000 km s-1. How can estimate the contribution of these processes to the energy and the momentum of the ISM?
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There is a large body of literature on this. ?There are basically two kinds of feedback from Stars to the ISM:
--Chemical evolution of the ISM
-Kinematic Feedback - which can involve shocks in terms of SN explosions but just massive star formation in spiral arms will do this. ? In some 2D velocity fields ?there is evidence for such kinematic star formation.
If all you want is an estimate, then make a model - how many SN events or O-Star formation events are there in the lifetime of a galaxy?
Note, in practice this is difficult, acretion disks or dense places in the ISM are likely the main inhibiting factors. ?The ISM is not a smooth environment at all.
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I am specifically looking for mass distribution and observed angular velocity of as many galaxies as possible.
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See the section "The Rotation Curves of Low Surface Brightness Galaxies" in attached first link. And also the last link. That has loads of data you looking for.
Other option is to look for articles and wikipedia and extract the data points manually or use some online available tools. I have attached multiple links below.
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(I already solved the problem by setting the keyboard to US English, I explain a message below)
I'm trying to use SpekCalc to simulate a X ray tube, but apprently it's not showing the bremsstrahlung radiation. I′m using a peak energy of 100keV, a theta of 16 degrees, and 5 milimeters of aluminium. But I obtain the same results whatever I have tried. I'm runing release 1.1 light for macOS, and I obtained the same results for windows.
Note: I'm using the values Nf=2 and p=1, instead of those ?suggested by Poludniowski because apparently the GUI is not accepting any value minor than 1.0. I have been trying other values with similar results.