- Abdulmunem Khudhair added an answer:What computing power do you use in your research? Does your group own computers, or do you use public resources?Research tasks require computing power, from PCs to supercomputers. What do you use in your work:
(a) my own PC/workstation is sufficient
(b) my group owns a computing facility (cluster, farm, pool etc)
(c) my group uses a facility provided by the lab/institute/university
(d) my group has an allocation at a national facility
(e) my group uses Grid or Cloud resources provided for free by other colleagues
(f) my group has funds to purchase time from commercial providers (Amazon etc)
(g) other (please elaborate)
Well I think most of us use option (a) my own PC/workstation is sufficient.Following
- Tolga Yarman added an answer:An old question that is still fresh: Is gravity a Newtonian force or Einstein space-time curvature?No gravitational wave was measured yet, no graviton was detected accordingly. On the other hand no space- time curvature was observable. There is no successful experiment to validate the current theories. What is the nature of the mysterious gravity? What is the velocity of this effect ?
This (http://vixra.org/abs/1409.0072) is a huge work you have achieved, Dear Setve, and Bravo to you... I have read it with great profit...
All the best to you, and to all of Colleagues present with us here......Following
- Vikram Zaveri added an answer:Can we use Kepler's third law to calculate orbital period of a star in a galaxy?
Kepler's third law yields correct orbital periods for the planets of the solar system
however, orbital period of the Sun in the Milky Way is computed with the relation P = 2*pi*r/v. Analysis given in the article "Supplement to periodic relativity" shows that we can obtain same result by introducing proper time in the form of deviation factor into Kepler's third law. This deviation to flat Minkowski metric satisfies Einstein's field equations and also provides solution to rotation curves of galaxies.
@Edgar. What do you mean by mutual repulsion of spiral arms?Following
- Ken Schatten added an answer:How can you get the temperature of a sunspot?
Hello, im working on a research regarding the correlation of the magnetic flux and different sunspot properties. And so far, there is no archive that has the data I need, is there an archive you could recommend that has the temperature for all sunspots which appeared from 2000-2005? or any equation that can give an approximation of a sunspot's temperature?
To me , the interesting thing is the Energy flux in sunspots, and how it radiates, and
the various energy transport mechanisms into and out of, the Sunspot..
I think the sigma T^4 formula is not bad for just trying to get some idea of a rough
temperature.. As Roger says, of course, there are complexitites involving the complex matter of light flowing into the sunspot, and all the "lines" in the atmosphere inside the spot, so , it is a very complex problem... To me, one can get totally overwhelmed by the complexity of nature, so perhaps some simple flat bottom to the sunspot, and a kind of chromospheric atmosphere above it, in a plane parallel approximation would do
well, to make some kind of associattion of temperature and radiated flux, etc...
There are many interesting variations, i think, in sunspots, as to whether they are growing, or shrinking too. as well as the various complexities as to whether one can view them as a bunch of field lines that inhibit the radiation into the spot, and that is why they are cold (Biermann), or that the convective energy transport and the downflows below the spot cool it, by taking neutral hydrogen from the photosphere to cool the energy transport into the spot... The dynamical approach is one that Gene Parker developed, and the equivalent "ion hurricane" approach one that i and my colleague Hans Mayr used in a simple analogy with our terrestrial atmospheric situation...
Anyway, they give us various questions to ponder that allow distractions from Earth.Following
- Igor Piskarev added an answer:Is there a reasonable alternative to the theory of the expanding universe?We know that our star, the Sun loses about 10^-14 of its mass per year as a result of electromagnetic radiation and particle emission. That reduction in mass should show up as a decreasing gravitational red shift. Same thing should happen to entire galaxies. But isn't it true that the galaxies we observe that are farther from Earth are also the younger we see (because light has taken millions of years more to come to us) and, as a consequence the more massive when we consider entire galaxies? (Because we cannot possibly see them as they are, but as they were millions of years ago.) Shouldn't we expect, correspondingly that the gravitational red shift of an observed galaxy will increase with its distance to Earth?
Red shift may be not Doppler's red shift at all, but absorbtion im matter, as vacuum is relict radiation (some kind of matter)Following
- R. Teixeira added an answer:What is currently the most accurate star catalogue to use for astrometric purposes?There are many star catalogues available, which star catalogue is currently the most accurate (maybe the USNO CCD Astrograph Catalog, UCAC4)?
In Ducourant et al. 2014 we have looked for the consensual proper motion and was just this that allows us to obtain a convergence in our trace back and so the kinematic age.Following
- Daniel Baldomir added an answer:Why are there no stable states with more than three or less than two quarks?
It is known that hadrons can be divided in baryons (fermions of three quarks) and mesons (bosons of two quarks). The sum of their electric charge is always an integer number, e.g. the proton is one and the neutron is zero. What is the reason that we have not found one particle with, say, five or seven quarks?
Thank you very much for your answer and sorry for my delay in responding. The application to cosmology is not obvious at all, but it seems that in the first moments previous to the hadron formation, around 10^(-35) seconds, i.e. in the inflationary age, it seems that the implications of having so massive particles could change the application of theorems as the of Borde-Vilenkin-Guth for singularities. I know that this far of my original question but it could help to understand a little better hypothesis as the dark matter, what do you think about?Following
- Cody Raskin added an answer:Proton- proton reaction in star center can anyone help?The proton-proton reaction in star center goes on for billions of years. But when the reaction starts on the surface as in the case of the nova, it only lasts for a few weeks. Can somebody explain this difference?
if you're having trouble understanding why convection turns on just when it has to, just consider that convection is an instability that occurs whenever the energy flux at the bottom of a zone exceeds that at the top. when that happens, energy builds up at the bottom and material rises through buoyancy until it deposits that energy somewhere else, and then it sinks again. the height it has to rise to before something else can take the energy away is the size of the convective zone essentially, and in stars, this happens whenever radiation can't do it at the bottom of the zone, but it can at the top, which can be because opacity is too high.Following
- Edgars Alksnis added an answer:How are the space and time related to biocentrism?Robert Lanza’s Biocentrism Theory
Space is as per Descartes/Newton; with time is a bit more complicated- but, believe, not in Your case.Following
- G. Bothun added an answer:How is the tagging of photons from astronomical sources, done?
How are the photons from different astronomical sources, which lie in the same solid angle from an observer, emitting in the same energy (i.e frequency or wavelength) region, tagged as coming from different sources? Does the Doppler shift play a vital role here? Or other techniques come in handy?
If you just have fluxes through bandpass filters, the separation is difficult and model dependent as discussed. If you can do integrated spectroscopy (often difficult) over the solid angle in question, you an do much better at resolving the individual components of the emission.Following
- Russell Jurek added an answer:What is the limiting magnitude for detecting a galaxy in the SDSS image?
It's complicated by the fact that SDSS uses "luptitudes", instead of standard Pogson magnitudes. SDSS Luptitudes are designed to asymptote to fixed magnitude values. This avoids the weird magnitudes that you would otherwise get when you integrate noise.Following
- Viacheslav Zgonnik added an answer:Looking for an advise on nebulae (molecular clouds, globules, protoplanetary disks)?
Our group of geochemists, geologists and chemists is looking for a astrophysicists or astronomer who will be interested to participate in our research. We discovered the correlation between ionization potential of elements and their abundance in planets and other bodies. This correlation could be explained by a simple termochemical equation. Predictions by this equation correlate impressively well with observed chemical composition of surface of planets. We propose a theoretical process which could explain observed facts. Details of our work are described in this document http://arxiv.org/abs/1208.2909
We are looking for a person who could help us (in collaboration way) to improve and connect our theoretical model with observations of nebulae.
It is correct. In our work we tested it on new data from space probes then interpreted the observed correlation as a Boltzmann distribution depending on the distance from the Sun. We tested our model on factual data for Moon, Mars, Venus and Meteorites. We find that predictions force of the model is excellent. Then, we made surface-to-volume analysis for elements. We find periodical trends, related with affinity of elements to hydrogen and with their mass. This suggests that radial differentiation of elements inside the planet was chemically- and gravity-driven. We have far more interesting results, which are out of scope of this paper.Following
- Louis Brassard added an answer:How significant is the discovery of Kepler-186f, an earth-sized habitable zone planet?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.
Three extremely large telescope project might be completed in the next 6 to 10 years:
The GMT, 22 m, 800 millions US$, 2020
The E-ELT, 39 m, the optical/near-infrared range, 1.2 billion US$, mid 2020s
The TMT , 30 m, near-ultraviolet to the mid-infrared, 1.2 billion US $, mid 2020s
These plan instrument are intended among other purposes to study the presence of water and life in exoplanets at different stages of formation, exoplanet atmospheric chemistry etc.
My question is how likely will the exolife existence question be answered in 10 years if we assume that one of these projects will succeed to be built?Following
- Joseph L Alvarez added an answer:Radiation can lose energy by collisions with other particles. Does all radiation tend to end up being infrared radiation?The loss of energy results in an increase in wavelength for radiation. If the time this progress takes is infinitely long, could all radiation (gamma, x, UV, etc.) finish with a larger wavelength.
Your question depends upon infinitely long. How and when we introduce infinity changes the results of a calculation. The result is a paradox if infinity is not properly introduced. A popular concept of entropy is that the entropy of a system increases. A closed, insulated system has constant entropy. When is it proper to introduce infinity in a closed system? Is the universe a closed system?
Suppose we begin with the most intense gamma ray burst attainable. The gamma rays will lose energy with each interaction with matter or other photons (except for some exceptions noted in other answers). Nevertheless, if this gamma ray burst occurred at the beginning of the universe, at the current age of the universe, we still have a probability that some of the initial gammas have not interacted. Is this a case of improper use of infinity, even if the probability is ridiculously small?
All the photons from the initial burst will have lost energy until some final gasp when that energy is absorbed in some process. We can say that the energy of the photons goes asymptotically to zero. So the answer to your question is that the photons degrade until they quietly absorb. That is the effect of carrying the equations to infinity.
If the universe is a closed system and the entropy does not increase, do we require continuous bursts of intense gamma rays? Will the universe finally degrade to the average with a small distribution in energy? I do not believe there is an equation that will answer these questions, but there is an equation that says a burst of gamma rays will asymptotically degrade to zero.Following
- Arnes Klisura asked a question:How does size of the objects in the Universe correlate to their characteristics?
What speed can be found in the microworld and what in the macro world and separately do smaller particles move faster or do smaller stars or galaxies or planets move faster? What color are smaller objects and what bigger object? Is there somewhere an interesting pattern? If there is an interesting pattern, what can we conclude from it?Following
- Loess King added an answer:How can I calculate the Earth's orbit, or what is the equation that enable us know its velocity vs. position at given time?
To Mitchell F. Struble:
Agree with the idea (really conservation of energy ), thanks.Following
- Josep M. Trigo-Rodríguez added an answer:What is the source of neutral sodium in comets?
Various authors have suggested sources in the dust tail, near the nucleus, in the plasma tail or some combination of all three (that might even turn off and on depending on what comet you are looking at at what time).
The two previous readings suggested are excellent as they review nicely our knowledge on Na in comets. Let me point out that if the general scenario of comet formation is correct we should expect the accretion of significant amounts of Na in these bodies, perhaps in neutral form forming part of the interstitial matrix (also in ices?). Its presence could fit our detected overabundance of Na in cometary meteoroids that could be consequence of extensive Na depletion of the inner disk during the early solar system stage. See e.g. our paper: http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004MNRAS.348..802T&db_key=AST&link_type=ARTICLEFollowing
- Victor Christianto added an answer:Can accelerated expansion of galaxies be explained as an expanding wave?
In PNAS, August 25, 2009 edition, Blake and Smoller argued that perhaps the standard terminologies of dark energy and cosmological constant are not required for explaining the accelerated expansion of galaxies. According to them, the key to solve that puzzle is to find expanding wave solutions of the Einstein's equations.
So do you think it is possible to use expanding wave solutions of the Einstein's equations to solve accelerated expansion of galaxies? Your comments are welcome.
Thanks Allan, for your answer. I will read your papers soon. Best wishesFollowing
- Victor Christianto added an answer:Do Einstein's equations correspond to solutions of Klein-Fock-Gordon equation?
I read somewhere that Einstein's equations may be expressed in terms of Klein-Fock-Gordon equation, but i am not sure yet how to do that.
In a paper, Fiziev and Shirkov discuss solutions of Klein-Fock-Gordon equation and its implications to Einstein's equations. In effect, this may imply that Einstein's equations have wave-type solutions.
What do you think? Your comments are welcome.
Thank you Stam, for your answer. Best wishesFollowing
- Michael Peck added an answer:Can Popperian falsifiability be applied to cosmology science?
While scientific cosmology rarely occurs in the work Karl Popper, nevertheless it is a subject that interested him. The problem now is whether falsifiability criterion can be used for cosmology theories.
For instance, there are certain issues in cosmology which have never been refuted, but instead the same methods are used over and over despite their lack of observational support, for instance mutliverse idea (often used in string theory) and also Wheeler DeWitt equation (often used in quantum cosmology).
So do you think that Popperian falsifiability can be applied to cosmology science too? Your comments are welcome.
Yes, I suppose if we view the discussion in terms of how things actually progress there are many additional aspects. I take a rather different approach compared to most in regards to forming hypothesis. Instead of taking a single observation and trying to propose a hypothesis or framework that will support it, I take ALL available observations into consideration. Then I begin to brute force the problem by thinking of every possibility that would support such observations. The best way to do this would be by starting with confirmed existence statements and only when the initial ensemble of classical explanations fails does one go to non-classical frameworks. In regards to where to look for a better theory, this would be it.
I will give an example of my own research in cosmology. I built the framework of my model on the grounds of a cosmological-scale gravitational potential, where the local deflection of geodesics into it provides the illusion of accelerated metric expansion; i.e. distant objects are accelerating back into the potential with respect to local observers (local redshift is actually more complicated than one might initially assume on this basis). Here I have a single hypothesis that is built upon facts, i.e. it requires the experimentally confirmed existence statements of geodesic deflection, gravitational/Doppler redshift and gravitational potential. Therefore, there exist no auxiliary hypothesis relative to the primary, which is the existence of a global gravitational potential.
From this I can derive redshift versus distance modulus, redshift versus angular diameter distances, redshift versus volume element, redshift versus time-dependence, large-scale B-mode polarization in the cosmic background radiation and several other predictions including local redshift anisotropy. Of course, for other predictions auxiliary hypotheses are required. Nonetheless, I have proven that one can have a theory with no auxiliary hypothesis that not only makes at least five precise and independent predictions, but in fact substantially out performs competing models that require a plethora of auxiliary hypothesis. Each prediction can further be applied to multiple tests, which you will find in my recently published article "Evidence of a Global Gravitational Potential".
In realistic cases, I would agree that one form of verification can be trumped by a stronger or more precise form later on. However, the 2nd form of verification will not necessarily contradict the first. A community may also choose to ignore observations that do not support their hypothesis, which is why one should actively seek to falsify their own model.Following
- Issam Sinjab added an answer:What is the origin of the magnetic field of a neutron star?After surpassing electron degeneracy and supported by quantum degeneracy pressure, these kind of stars are composed mainly by neutrons, particles without electic charge. They posses nevertheless very strong magnetic fields. So, if they are composed mainly from electrically neutral particles, what is the origin of their strong magnetic fields?
Dear Marek Wojciech Gutowski
Sorry for my late reply as I am on holiday and I should explain better my earlier post and point out some of the difficulties that come with the conservation of magnetic flux assumption especially in connection with magnetars.
"Where from did you get "the conservation of magnetic flux"? "
Well, it was first suggested by Manchester & Taylor (1977) and by Smith (1977). See for example:
Manchester, R. N., & Taylor, J. H. 1997, Pulsars (San Francisco: Freeman, W.H. & Company).
Also, please refer to Jeremy Heyl's post dated Dec 4 2012:
"The electrical conductivity is very high so that over the timescale of the collapse of the star the magnetic field lines cannot move far relative to the collapsing plasma, so the magnetic flux threading the core is conserved Flux ~ B R^2 so as R decreases the field increases."
There are however serious problems with this assumption as we shall see below.
A large value of the magnetic field near the neutron star's surface is customarily assumed to be associated with magnetic flux conservation during gravitational collapse, also called fossil field hypothesis. The simplest and most popular hypothesis, magnetic flux conservation, is that neutron stars magnetic fields are simple remnants of their main sequence (MS) progenitors. For a star of radius R and surface magnetic field strength B, Conservation of magnetic flux in gravitational collapse require the magnetic flux BR^2=constant. Consider a star of B=100G and R=7x 10^8 m. If a star of this surface magnetic field strength and radius collapsed to a neutron star of radius R(ns)=10 km, it would have a surface magnetic field of B(ns) equal to about 10^11 G. Admittedly, this is unrealistically optimistic estimate because the neutron star contains only some 15% of the progenitor's mass! The other major problem of course, as you rightly indicated, is that the magnetic field strength 10^11 G is at least 1-4 orders of magnitude weaker to explain magnetars with magnetic field strengths 10^12-10^15 G. The fossil hypothesis is therefore not an attractive one, at least not for magnetars.
One could argue that some MS stars have much higher fields, the strongest fields known in MS stars are around 10^4 G. Magnetic flux conservation during gravitational collapse of these stars would imply B(ns) equal to about 10^13. Not only is this still insufficient for magnetar but there is also a problem of statistics. Only a very small fraction of progenitors has magnetic fields as large as 10^4 G. Magnetars, on the other hand, are born frequently. Their birth rate is probably comparable to that of normal neutron stars-Woods(2008).
One other serious problem of the magnetic flux conservation is that not only the neutron star contains only some 15% of the progenitor's mass but also the core of a typical progenitor MS star occupy only some 2-3% of the star's cross section!
Here's a research paper that attempts to explain the phenomena using an approach for induced magnetic moments in neutron superfluids:
The Physics of Strong Magnetic Fields in Neutron Stars:http://arxiv.org/ftp/arxiv/papers/0706/0706.0060.pdfFollowing
- Milan Krkoska added an answer:Can fracture mechanics predict when the whole Universe will fracture?This question is open for chemists, metallurgists, physicists and astrophysicists:
Check out this diagram which has been released today on Universe inflation. It describes how the universe has been expanding with time. It says that the Universe, around 2 billion years after the Big Bang inflated at a rate of 1% every 44 million years. The expansion decelerated under the influence of dark matter before the expansion continued under the influence of dark energy.
Now Let's look at another [quite similar] diagram, called creep diagram:
The diagram describes the elongation of a structure under a static load with time, across three stages before fracture.
It happens that a certain concept in a scientific field can be used to describe (and predict) a phenomenon in a seemingly (and sometimes totally) different scientific field.
Can these two diagrams help make the case, one day?
are you elaborating on your idea? just out of curiosity ...
- Manikandan B added an answer:Whether light travels through Pure Vacuum or Not?
I need to know whether light particles travels through pure vacuum? Also I need to know what is pure vacuum? (or) what is vacuum ?
Hi James Garry
Thanks for great answer if possible can you send me some references regarding this Q&A ? that will help me to understand this clear way....Following
- László-Attila Horváth added an answer:Could some of the fundamental constants be functions of the gravitational potential?
Based on several assumptions to deduce a cosmological model with three fundamental constants including the speed of light in vacuum, the Planck constant, and the gravitational constant, along with the dimensionless electroweak coupling constant turned into functions of the gravitational potential. Initial research of this model has indicated solutions to avoid the singularity in both special relativity and general relativity.
IAs geologist engineer considering the Earth like object of research, the physical laws are onto planetogical scale… Newton interpretation was made such of scale… We know well that in time of Newton’s life, the geology like an independent science did not exist… From this and from the new data obtained (geological scale, solar system scale) exist lot of phenomena which cannot explained even if we are using universal constant of physics… My explanations are so simple that I do not need universal constant…Following
- Jesús Varela López added an answer:Is anyone interested in the full data release of the ALHAMBRA data?The ALHAMBRA survey (http://alhambrasurvey.com/) has just published its 1st full data release.
You can find the the data (catalogs with photo-z and synthetic F814W images) through the following links:
* web server: http://cloud.iaa.es/alhambra/
* FTP server: ftp://ftp.iaa.es/alhambra
* Spanish Virtual Observatory: http://svo2.cab.inta-csic.es/vocats/alhambra/index.php
the description of the data in the catalogues can be found in Molino et al.(2014) paper:
If you have doubts about the content of the catalogues, I would suggest to contact directly the first author (Dr. Alberto Molino).
Regarding the public images, you are right, they are indeed the synthetic F814W images reconstructed from the narrow band images. The way in which they have been constructed is also explained in Molino et al.(2014).
Finally, with respect to the NIR images, I'll try to find out whether they will be made public.
- Michael Clark added an answer:Does anyone know of any commercial high-reflectance (>98% in 300-400 nm) mirror film (thin flexible film)?I am looking for reflective mirror film (specular flexible film) which has high reflectance (>98%) in the UV region (300 - 400 nm) in order to use it in our astrophysics project. There are some products in the market (e.g. ESR by 3M), but all of them do not have high reflectance for wavelengths below 400 nm. It is technically possible to make such film if multi-layer coating is used, but a custom order will be very expensive.
I would very appreciate it if you could tell me any nice products.
I always wanted to try to make a mirror using two sheets of glass where
there would be an evacuated air space between the two sheets of glass.
One thin would curve down , while the other one would be thicker and more
resistant to changing shape. They would be separated by a ring of
uniform height at the perimeter and glued to both the upper and lower
circular cut glass slabs. I suspect the mirror could only be used in
a horizontal plane because tilting would warp the mirror and the image
due to Earth's Gravity. I also though of injecting a hot plastic between the
two layers, and seal it while hot, so upon cooling it would pull down the
thinner glass sheet using the thermal coefficient of contraction
of the plastic ( contraction on cooling creating a near circular or parabolic
mirror ) minimal grinding required. Since the mirror is the most expensive
part of a telescope, keeping its cost low, will aid in keeping the cost low
for the telescope.Following
- A. V. Uryson added an answer:What is the structure of black holes?In some books popularizing science (e.g. “Astronomy for dummies” by S.P. Maran) it is written that black holes have the following structure: falling matter, event horizon, singularity. This structure does not coincide with the classification used in special literature where the accretion disk forming by falling matter is included. Is the black hole structure in the book above an adequate explanation for non-specialists?
Dear Nainan, many thanks for the reference.Following
- R.C. Gupta added an answer:If one can invent a theory in which matter and antimatter repel one another, what does it predict for things which are neither matter nor antimatter?Do matter and anti-matter really react or bombard with each other?
- Gravity is a real physical force, not an 'artifact' of curvature (general relativity). My gravity-theory (see the paper/link mentioned below), based only on special-relativity, predicts that though particle & antiparticle attract, but "matter & antimatter would repel each-other". R.C. Gupta, ‘Gravity as Second-order Relativistic-Manifestation of Electrostatic-Force between Atoms of Two Bodies’, www.arxiv.org/abs/physics/0505194, May 2005.
- Even 'general-relativity-tests' could be explained 'without general-relativity'; (see the paper/link below). R. C. Gupta, Anirudh Pradhan, Sushant Gupta, ‘Refraction-Based Alternative Explanation for: Bending of Light Near a Star, Gravitational Red/Blue Shift and Black-Hole’, www.arxiv.org/pdf/1004.1467 , April 2010. Dr.R.C.Gupta, Visiting Professor, I.E.T. Lucknow. email@example.com
- Stephen Warren added an answer:If it's confirmed that there has been something before the "Big Bang", what do you think about that "something"?Is anybody able to Imagine "Nothing" before the big bang? Does it mean no time and no space. Well, I cannot imagine there were nothing before the big bang. I think it might be something. But what about "something"? For me, this is the main question?
In "The Life of the Cosmos" Lee Smolin argues (or perhaps conjectures) that every black hole is the source of anew big bang and a new universe. If it is assumed that the daughter universes each have physical laws similar to those of their mother then the multiverse should be dominated by those with the highest rate of black hole formation. Smolin admits that he hasn't done a real analysis but that some back-of-an-envelope calculations suggest that any significant change to our physical laws would tend to reduce the number of black holes formed. So ... maybe we are a typical member of the multiverse.
What happens when the universe ages to the point when black holes evaporate? I guess we all go together (more or less) when we go.... unless you believe in block time, where past present and future already exist and time is not a turbulent river but a frozen lake.Following
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