Astrophysics - Science topic

You can find free and good impact factor journals related to your field in the master journal list of Web of Science.

Wonderful question and interesting discussions.🌷🌷🌷

Fondest regards

I hope my disproof of Gravitational Waves is not discouraging anyone from making the experimental results maximally water-tight.

For it is only the truth that everyone is interested in in science.

The mass associated to kinetic energy is negligible in a galaxy, or in galaxy cluster, in regard of the rest mass at the source of Newtonian or Einsteinian gravity. The relative additional mass caused by kinetic energy is of order (v/c)^2, where v is the average (virial) velocity and c the speed of light. Most galaxies have a v in the interval 50-350 km/s and in galaxy clusters 200-1500 km/s, in regard of 300'000 km/s for c. For galaxies those with most dark matter fraction have a low v, so dark matter anticorrelates with v.

Horst Stöcker has a patent for converting mass into energy with mini black holes. The idea is to collide normal matter, e.g. from the garbage bin, with a mini black hole. The Hawking radiation that comes out can be used as a heat source.

Mini black holes can be manipulated (fixed, accelerated) with electric fields, if charged.

Regards,

Joachim

No. Chaos is not because of Hubble's Law.

The chaos is because of 'General Relativity'.

Weitter Duckss "Astrophysics today (and before) is a fabrication of nonsense. "Scientists" (based on astronomical observations) fabricate their results without evidence (mostly)".

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.

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)

Hi! I don't know if it would help but this article is about hapke modeling calculations with IDL.

📷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

Recommended / Share

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

Following.

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.

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

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).

Do you have any good abstract for this topic in your mind? Please feel free and share with us.

Dear Preston,

Intriguin view, thanks for sharing Vera Lima

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".

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).

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

Thanks a lot for positive feedback

Surely no

Best Regards Nasser Farhat

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..

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.

Regards,

Emad

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.

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.

Nice discussion...

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:

https://www.researchgate.net/publication/266393167_OPTIMAL_NUTRITION_AND_CELLULAR_LIFE_PROLONGATION_IN_THE_LOH-THEORY_CONTEXT

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.

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?

The charged dust-dust interaction is electrostatic in origin. What is the expression of the interaction potential?

Reply and reference are welcome.

An appropriate answer to the above question is kindly requested for your needful action as early as possible.

All are kindly requested to answer this question with full energy

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.

I agree with Dr. Dariusz Prokopowicz

Steven Sesselmann

" 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.

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.

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.

Search to measure mental construct

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.

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".

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.

I am grateful to you all for answers and references.

Hope this discussion to continue.

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.

Once again, as JPG image

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.

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'?"

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.

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

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

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.

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:

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?

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.

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. 

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.

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 ;-)

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.

It depends.

 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

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 

“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

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

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%).

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.

Maybe you can simulate the relationship between sun, moon and earth with two ball and a light

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

Fluids don't propagate transverse wave modes but light is polarised hence must be transverse.

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.

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.

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".

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

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.)

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.

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

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.  

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.

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.

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:

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

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.

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