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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.
Questions related to Astrophysics
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I need some guidance to understand and properly use MESA.
My ultimate goal is to modify it such that I can use a variable G.
I saw a video using it to predict the evolution of a main-sequence star. I don't quite understand how it is used to predict observations (Stellar Population).
I am familiar with the Kennicutt-Schmidt Law, relating the rate of galaxy formation and gas surface density
The Tolman surface brightness test (surface brightness versus z), might be used together with wavelength information to determine star population as a function of z.
Then there is the initial mass function
It is not clear how this initial mass function would be changed in an epoch-dependent G.
IN SUMMARY
This is a very early stage of exploration of the issue of Stellar Population Modeling, Star Evolution under MESA.
Advice and comments are welcomed.
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My problem with MESA are:
a) I didn't know the existence of three mesa programs. I knew about the modules program and the SDK. There is at least one more related to Graphics. I tried to install the graphics program and after doing so, I had to reinstall my OS. Installing the requirements screw up my nvidia driver choices or something.
b) Now with the OS recovered, following the installation procedure doesn't lead to a working program. So, there is where I am - with the benefit that now I know about the MESA list-server and will be asking for help soon.
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In reference to the attached document, it seems that scientist with the helping hand of metaphysics have created several scientific versions of Turtle All the Way Down viewpoint.
The article criticizes two widely accepted models for the genesis of the universe which can be listed under two hypotheses:
  1. Nothing
  2. Something
Both theories have been discussed in enough detail, but this question/discussion is related to the second theory.
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Talk about ancient hoary tales... The cyclic universe theory was an alternative attempt to allow fro a Universe of infinite age, a la the Steady State Theory, despite the compelling evidence for an actual beginning. It relied on the idea that the Universal expansion wouldl eventually slow, reverse, and the Universe would then collapse to a singularity; but instead of just ending at that point, it "bounces" and repeats the process, over and over and over (ad infinitum) However, there are two insuperable problems with the idea. First, the Universe is not slowing down (it once was, but about 6 billion years ago the increasing amount of empty space created by the Universal expansion caused the tendency of more or less empty space to increase the rate of expansion to overcome the tendency of mass (via gravity) to decrease the rate of expansion, since although there is always more and more space, there is never any more mass, which was the idea behind the Steady State theory), but is instead expanding at a gradually increasing rate (probably asymptotically to some fixed value about half again the current rate), so it will NEVER stop expanding or collapse in the first place. The other problem was that it didn't take long to show that IF the Universe COULD have collapsed and then "bounced", there would be an inevitable increase in the entropy of the "new" Universe, and the current entropy of the Universe is so small that IF the cyclic Universe theory had been correct, our CURRENT expansion would be the VERY FIRST ONE, which means that the goal of making the Universe infinitely old was destroyed, thereby also destroying the original purpose of the theory. Because of this, this is the first time in close to 50 years that I've heard any reference to the theory other than as an example of good ideas gone stale and rotten; and I am sure that no matter what arguments have been made in its favor, they are, as one of my mentors, Lawrence Aller, used to say, "rubbish".
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I agree that Astrophysics is a multidisciplinary field and that students of Astrophysics are taught many subjects from diverse fields. For example Astrophysics curriculum covers mathematics, relativity, statistical mechanics, quantum mechanics, fluid mechanics, thermodynamics, radiation, lasers, electronics, optics etc. etc. But I am perplexed to find that neither Astrophysics text books nor the study curriculum of Astrophysicists cover theory of elasticity in general or working out stresses and strains in solid bodies in particular.
An obvious answer of most learned readers may be that Astrophysicists are not required to deal with solid bodies throughout their career and hence are not required to study theory of elasticity or to learn working out stresses and strains in solid bodies.
Actually however, the situation is other way around. Since Astrophysicists do not study theory of elasticity and do not know how to work out stresses and strains in very large spherical solid bodies under self-gravitation, they erroneously make them collapse under self-gravitation into black holes, thereby misleading the whole scientific community.
None of the current models of stellar core collapse make any attempt to compute the magnitude of STRESSES in the SOLID iron cores actually produced in massive stars at the end of their fusion burning stage.
As per current models when a solid iron core becomes degenerate, the degenerate electrons get freed from their parent iron atoms leaving behind 'positive ions' of iron. When the positive ions start falling towards the center of the core under gravity, the high energy degenerate electrons are SUPPOSED to push these ions outwards by their degeneracy pressure to counter the effect of gravity. However, to impart an outward push to the falling ions, the high energy degenerate electrons will have to exchange their momentum with the falling ions through elastic collisions. But the high energy electrons cannot exchange their momentum with positive ions through elastic collisions because of their electrostatic interactions and hence can never provide the so-called electron degeneracy pressure in stellar cores to counter the effect of gravity.
The main reason for ASSUMING the electron degeneracy pressure in solid iron stellar cores is the implied belief that a cooled down stellar core cannot maintain its Hydrostatic equilibrium in the absence of adequate thermal pressure and that nothing else can stop the gravitational collapse of such cores. Therefore, the constituents of a solid stellar core are first ASSUMED to be non-interacting for applying Hydrostatic equilibrium equations and then the electrons and ions are again ASSUMED to be non-interacting for invoking the electron degeneracy pressure to support the pull of gravity.
Hence, it turns out that all stellar cores which are said to be degenerate, where some sort of degeneracy pressure is invoked to prevent their gravitational collapse under Hydrostatic equilibrium conditions, are in fact SOLID stellar cores which acquire their stability through Equilibrium equations of elasticity. In current models, the stresses in a solid iron stellar core are never analyzed as a SOLID body under self-gravitation, by using the Equilibrium equations of elasticity. By taking into account the electromagnetic interactions among electrons, protons and ions we can show that the high density stellar cores transform into gravity induced solid state which can support the gravitational loading through development of radial and hoop stresses.
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Thanks for your response and I respect your opinion.
You wrote : "...The inner core of stars is not made from solid iron (iron-nickel)"
Stars of mass greater than ten solar masses, go through various stages of core and shell fusion of heavier elements finally ending with a core of iron. These iron stellar cores are normally surrounded by fusion shells of Si, O, C, He and H. The quasi-equilibrium Si shell fusion continues to grow the iron cores up to certain limit. Under high pressure and density environment prevailing in stellar cores, the mean separation between two adjacent iron atoms or ions will be much less than the normal free size of iron atoms. This leads to grid locking of these atoms or ions in a lattice structure.
In situations of very high core densities, atoms and ions will occupy relatively fixed positions and may experience thermal vibrations about their mean positions. When the mean separation distance between ions is less than the normal mean size of their parent atoms, of the order of Bohr radius or less, the electrostatic repulsion between the ions will force them into a lattice gridlock, leading to a solid state. In a solid state, particles maintain their normal separations through mutual interactions and cannot move past one another. It must however, be kept in mind that this is not a ‘naturally’ or freely occurring solid state but a ‘forced’ solid state brought about under extreme gravitational loading in a stellar core.
This has been explained in greater detail in section III. "Invalidity of Electron Degeneracy Pressure Model" and section IV. "Final Solid State of all High-density Stellar Cores" in my paper titled, "Stellar Core Collapse Models are Erroneous and Misleading".
In a solid state the mutually interacting constituent particles are mostly at rest, apart from some thermal vibrations about their mean positions. The mean positions of these solid-state particles constitute some sort of geometric pattern, a lattice structure. When some external force is applied to one or more of these lattice particles, the mutual separation distances between the adjacent particles in the vicinity will slightly change so as to produce additional reaction forces just to balance the externally applied force. This slight change in separation distances, which implies a slight change in the lattice structure, can be described as slight deformation of the lattice structure. If the externally applied force is now removed, the change or the deformation in the lattice structure will also get eliminated and this characteristic of the lattice structure can be described as elasticity of the solid ensemble of interacting particles. In fact, quantification of the magnitude and direction of the deformation by a displacement vector produces the best characterization of the elastic nature of the solid. Thus, central regions of all stellar cores will physically constitute a solid state. Stresses induced in such cores due to self-gravitation can only be analyzed by study of its displacement vector field through equilibrium equations of elasticity and not by hydrostatic equilibrium equations of the kinetic theory.
Best Regards
Gurcharn
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The available source https://ingenieria.uatx.mx/orionfrg/cry/ currently doesn't have the dataset. The existing artIcles also mentioned the link. However, unable to find the dataset.
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Good morning, Mr. Samrat!
Your welcome!!! Have a nice day !!!
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The offended paper is here:
This is a rhetorical question since, in my mind, that is utterly non-acceptable.
I say that while accepting the reality that it takes time to write a few paragraphs in a rejection letter.
That said, it might take years to polish the arguments contained in a paper.
In my case, it took 16 years.
My issue is that, on purpose, I chose to tackle the Big Bang Theory first. It is the weakest model in the whole Physics. There are "Crisis in Cosmology" articles written by everyone and their cats. There is Hubble Tension, S8 tension... Missing Dark Matter, Early Galaxy Formation Conundrum...
Not to mention the lack of any evidence of a False Vacuum, Inflaton Field or Inflaton Particle, etc, etc.
My theory starts with a new model for matter, where matter is made of shapeshifting deformations of the metric (so, it is not Mass Deforms Metric, but modulated metric is mass).
It cannot be simpler. It allows the Universe to have just space, deformed space and time - the simplest possible model.
Occam's Razor will tell you that this model should be part of the conversation.
The Universe starts from a Heisenberg-Dictated Metric Hyperspherical Fluctuation, which after partial recombination is left with an Inner Dilation Layer (IDL) and the Outermost Contraction Layer (OCL).
As one would expect OCL breaks apart when it starts to move, pushed by the IDL. This process has a physical analogy in the Prince Rupert Drop
SO, the model is disappointly simple. No metrics, nothing for you to polish... just a simple model that explains EVERYTHING.
It also debunks General Relativity (Einstein's equations do not describe the Universe expansion). And replicates all Einstein's successes, while providing simpler explanations (instead of time dilation, we have the weakening of forces with absolute velocity).
What about ABSOLUTE VELOCITY? Well, we all know we can define absolute velocity using the CMB. Period. So, absolute velocity (and the breakdown of Relativity) shouldn't be a surprise.
So, my theory also challenges the current Cosmic Distance Ladder and in doing so (using an epoch-dependent law of Gravitation), it parameterless predicts the distances using just the redshifts. The predictions are attached.
So, in doing so, it attacks Dark Matter and Dark Energy and all the sordid interests behind them. I say sordid in the sense that I believe that all these entrenched interests are at play in this summary rejection of my work.
Why would I say that? There is a simple reason. If an editor (and all the other editors) don't bother to justify their actions, one is left with nothing to do other than speculate on the WHY.
Why is it ok for preprint repositories to block my already published work?? That is happening (and happened during the last 16 years) at the Los Alamos Archives.
Why would it be ethical for an editor not to write a single paragraph pointing to an specific scientific reason for yanking a paper out of the review process?
How calous these people can be with respect to Science and Mankind's Future? Science is the key to the Future. It shouldn't be at the mercy of unconfessable motivations.
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Prof. Marco Pereira: Do you support the preprint solution when you said "In addition, preprint repositories (Los Alamos, preprint.com) should always allow already published work to be posted."?
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Recent numerical simulations show that the inner part of the disk seems to oscillate in presence of a Large scale magnetic field or when the disk is in MAD state. So, can we correlate this sort of behaviour with the variability of the source?
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Strong Magnetic field inside the compact object plays the crucial role for understanding the variable x-ray burst. Change in internal structure due to the presence of superfluidity, superconductivity and external accretion also are responsible for this variable x-ray burst. What I understand that we have to consider these three first and then to compare with the simulation where the effect is changing, finally we will be able to understand what is actually going on.
Simulation can help us to know the magnitude of possible change and its location to find out inside the compact object.
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I would like to publish my Scientific Preprint Paper free-of-charge in an international Astrophysics journal with a satisfactory Impact Factor. Can you please suggest such a journal?
I have published my Research Results on a New Orbital Model for Moving Bodies in the Universe that I am asserting as a result of my scientific analysis, which can be found below:
"Everything Is A Circle: A New Model For Orbits Of Bodies In The Universe"
I will be presenting this work to the general scientific community at #COSPAR in Sydney, Australia, which will be broadcast Live according to Congress schedule on February 2, 2021
and will be available as Video-On-Demand in more detail.
To provide an introductory idea for readers and scientific community in general, here is a short video giving an overview description of the main and most significant findings:
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Also a good suggestion would be Astronomy&Astrophysics with impact factor of ~ 5.8 as of 2020. There are no page charges for authors from sponsoring countries (find the list below):
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We all know that accretion disks around BHs are presumably be magnetized in nature. If we consider ideal MHD, we know magnetic fields are frozen within the plasmas. Now, magnetic fields are turbulent, so can they help in raising the temperature of the disk? And is it significant?
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The Boltzmann interpretation of temperature is that it is related to particle velocity. Considering that many of the particles in an accretion disk are expected to be electrically charged the magnetic field would be expected to cause a geometrically anisotropic distribution of temperature and associated thermal effects. This obviously complicates analysis of the thermal profile.
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Dear Researchers in the field :
Does anyone know what the KAGRA Gravitational Waves Observatory it's been up to ?
KAGRA announced at the end of last year (2019) that they were ready for the kick off. And that in February this year (2020) they were turn to the sky for the first (real) observations and be ready to joing the efforts of the LIGO-Virgo collaboration.
But I haven't hear anything about KAGRA since that time.
I'm sure they had to close due to the COVID-19 pandemic, probably since March.
But, now in December, almost the end of the year, I would have expected to hear news about Observatory.
Does anyone know what is it status nowadays ? Maybe the explanation is that the facilities kept shut down almost the whole year since the pandemic.
If someone know fresh news, I'll appreciate the sharing.
Best Regards all ! :)
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Discovered the following publications which i shall be reviewing and highly recommend the members here to as well. From KAGRA.
[2201.01397] Inferring Astrophysical Parameters of Core-Collapse Supernovae from their Gravitational-Wave Emission (arxiv.org)
Phys. Rev. D 105, 023004 (2022) - Merger rate density of stellar-mass binary black holes from young massive clusters, open clusters, and isolated binaries: Comparisons with LIGO-Virgo-KAGRA results (aps.org)
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Do such measurements make sense? Do they exist?
Comparing redshift and luminosity distances, if that is a sensible question, may bear on the 4/3 scaling hypothesis as it relates to dark energy.
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Cepheid and RR Lyrae variables are well known standard candles, and important tools in the cosmological distance ladder. For example, Cepheid variables, which were discovered by Henrietta Swan Leavitt, have the property that their luminosities can be directly inferred by observing their pulsation period, which then allows one to calculate their luminosity distance, given that the observing instrument (telescope) also measures their flux.
However, although nothing stops you from making redshift measurements of relatively nearby objects, this will induce an error in any cosmological parameters inferred from these measurements (such as the luminosity distance), because the peculiar velocities of these objects would be comparable to their Hubble flow, giving you highly inconsistent results. Luminosity distances calculated by interpreting the measured redshifts as cosmological redshifts, become more reliable at larger distances, where the Hubble flow dominates over the peculiar velocities.
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I want to create preprint of a research article via arXiv. Do you recommend any specific latex template?
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I conducted a experiment whose conclusions were opposite as that of Big Bang. So, based on the conclusions of my experiment I concluded that some points in Big Bang Theory are wrong...
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I am in agreement that the Big Bang theory is not correct:
Furthermore I think that the current ideas about the formation of the solar system need revision:
I hope this helps.
Richard
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The existence of turbulence in astrophysical fluids has been living as a well-known unsolved problem for a couple of decades. The range transitions among three distinct scales of the micro-fluidic kinetics are still lying obscure. In this context, is there any equation of state to describe turbulent fluid media in the fabric of the modified (by turbulence) macroscopic Navier-Stokes equation?
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Dear Professor Karmakar
Can you please explain which conventional equations are you talking about for turbulent fluids?. Is there any equation available for turbulent fluids?
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There are several papers which are using following formula (as shown in the picture) to calculate the dust mass (Md) of the dusty environments such as Nebula, loops etc in the ISM. The expression for dust mass shows that it depends on grain size, grain density and grain emissivity, here, for IRAS Survey, grain size = 0.1 micron, density = 1000 kg/m3 and emissivity = 0.0010 for 100 micron, respectively, are used. Are these constants same for AKARI and WISE survey too? OR, are there any other methods for the dust mass calculation using AKARI and WISE data? I would be very much happy to get your valuable suggestions. Thank you :)
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The grain size, density and emissivity are not properties of the data/telescope (IRAS, WISE or AKARI), but of the physical objects you want to study. Hence, deciding which parameters to use is complex and must come from your knowledge of these objects. Have a look on how these parameters were derived from IRAS data - what kind of objects, assumptions, conditions? If they roughly can be applied to the objects you want to study with AKARI, then you can justify using the same parameters. If your objects are completely different then you need to somehow derive or find a different set of parameters (or at least a range of possible values).
Good luck,
Michał
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..
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Because we always wonder;
- where we came from,
- how we were created,
- who we are...
And questions like that...
I think we realized that we can't answer these questions just looking our home(earth).
Universe tells us the past, present and future. And it makes me really very excited. 🤩
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Dr. Hans-Otto Carmesin is a prolific theoretician who wrote among other things, these two books:
Modeling SN1a data:
That said, he leads a field where a lot of unsupported claims are tossed around without anything to support it. That is why they are unsupported..:)
As Dr. Carmesin professed, scientists should follow the teachings of Aristotle and always use the simplest possible model that is consistent with Reality.
Dr. Carmesin's model has nonlocality, dimensional transitions, the usual suspects (Dark Matter and Dark Energy), and an epoch-dependent Dark Energy (figure 8.15 on the first book above).
It is a fantastic work and from my point of view, unnecessary and incorrect.
Unnecessary because there is HU which is capable to explain everything Dr. Carmesin explained without the need for a Big Bang, Dark Energy, Dark Matter, epoch-dependent Dark Matter, Polychromatic Vacuum. Because of that, Aristotle and Occam's Razor would support HU and rebut Dr. Carmesin's work.
Attached is my summary of the problems I found on Dr. Carmesin's claims that SN1a distances support his work.
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This is an ongoing discussion.
Dr. Carmesin provided a reply to my objections and confirmed that he is not sure if his model can predict the SN1a distances.
In fact, he said: "My theory does not fail to predict these distances. I just did not calculate these distances yet for a good reason: I tested my full theory by calculating the measured Hubble constants of the Hubble tension."
First, that is not a good reason. Second, I calculated the distances according to his model and the model failed. See the plot and the attached python script.
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My plot of his model showcases that the model fails to predict the observed distances.
I also drive home the fact that Dr. Carmesin's model modifies the meaning of H0 (the Hubble Constant). Because of that comparison of results are not straightforward and seems to not have been considered before.
The plots also show that HU model predicts the observed distances without any parameters.
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Dear Hans-Otto,
I thank you, in the name of all the readers, for your books and wisdom.
I also derived Quantum Gravity and offered everyone these articles.
I remind you that my work has no parameters and that my prediction for the G-dependence of the Absolute Luminosity yielded a G-factor that was off just by 11% from the observed.
My Quantum Gravity theory predicts the maximum density inside a Black Hole and creates Matter directly from deformed space.
Here is the maximum density inside a Black Hole:
I also predicted the position of Earth in the Hyperspherical Universe and replicated the CMB observations (together with the spherical harmonic spectral decomposition). I did that using interdimensional hyperspherical harmonic spectral decomposition, after a grid search for the best location. Here is the grid search:
Here is Planck's CMB observation:
and here is the hyperspherical harmonic acoustic spectral simulation of the same:
at Earth's position:
χ= 339.46 degrees
θ = 341.1 degrees
ϕ= 104.08 degrees
More details here:
Here is the Equation of State of the Universe:
Here is the 3D Map of the Observable Universe:
CENSORSHIP
My theory has been published since 2007 and it has been censored at Los Alamos archives and mainstream journals (including the one where Dr. Amendola is the editor)!
You have your voice. You are allowed to publish your work. I am not.
I have a story to tell, one that is distinct from the story you tell and that everyone wants to hear.
Can Scientists handle that? Science should be able to do so.
I would like you to offer to be my endorser at Los Alamos Archives.
Best Regards,
Marco Pereira
PS- Please confirm that your theory failed to predict the SN1a distances and please provide me with its E(z).
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This is to understand how the concepts of statistical mechanics is applied in astrophysics.
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Hi,
I learned a lot of that relationship in:
there are several chapters where the it is clean and well explained.. so enjoy,
regards,
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A Cosmology based on a Chaos-borne Hubble Law
Otto E. Rossler
Division of Theoretical Chemistry, University of Tubingen, Auf der Morgenstelle 8, 72076 Tübingen, F.R.G.
Abstract
A recent classical-mechanical finding, Fermi deceleration, implies a classical Hubble-like law. While its exact size is still open, it is bound to co-determine empirical reality. Some old and new questions concerning the size and the age of the cosmos arise. The current enigma of early old galaxies supports the prediction of a potentially much larger and older cosmos. So does Riccardo Giacconi's finding of ultra-high-redshift x-ray point sources.
(October 8, 2004)
Recently, a classical-mechanics based Hubble-like law was described [1,2]: Light rays
negotiating galactic clusters that are in random motion with up to 1 percent the speed of light (as is realistic) suffer a distance-proportional redshift through "Fermi deceleration." The latter phenomenon was discovered by Loskutov et al. [3] on a chaotic billiard: A fast-moving, low-mass billiard that is subject to random grazing-type collisions with slowly moving high­mass boundaries suffers a distance-proportional loss of momentum called Fermi deceleration [3]. The repelling grazing-type boundaries of Loskutov et al. can be replaced by attracting high-mass point centers - with the same grazing-type interactional effect. The slow attracting centers may be galaxies or clusters of galaxies and the billiard may be a light ray. The size of the effect depends on the density, mass and speed of the attracting centers.
The size of the effect appears to be neither too large nor too small to accomodate the empirical Hubble law [1]. If this preliminary result is taken as a cue, the implied lack of cosmic expansion re-opens the age-old question of the size of the cosmos. Fortunately, perhaps, a general-relativistic size limitation remains in charge if the mass density in the cosmos is uniform. In this case, not too much is changed compared to the standard paradigm: The cosmos can still be a pulsatile cosmos, for example, albeit so on a longer time scale.
If the assumption of a uniform mass density is dropped, on the other hand, the general­
relativistic bound is no longer finite. This stationary solution to the original Einstein equations was discovered by Benoit Mandelbrot [4], a fact which is not very well known. If the fractal dimensionality of the mass distribution is assumed to be unity (so that twice as large a radius contains not eight times but only twice as much mass - as in an ultra-light hole­ ridden Swiss cheese), the Schwarzschild radius which limits the size of the cosmos becomes infinite. For twice as much mass by definition has twice-as-large a Schwarzschild radius (and so on), so that no finite limit is reached in the present case. An exactly 1-D Mandelbrot cosmos is both stationary and unbounded. Peebles almost immediately found that the empirical fractal dimensionality of galaxies is about 1.2 up to large distances [5]. This and subsequent data can be re-evaluated by dropping the original assumption of a progressive lack of volume as the remaining distance to the primordial fireball shrinks toward zero. The validity of Peebles' near-unity result will thereby be extended to covering the greater part of the visible universe.
If this prediction is correct, a "Brunian cosmos" (in honor of Giordano Bruno) of potentially unbounded extension in both space and time becomes an option again- But would not the other "pillars of the big bang" automatically preclude so far-reaching a conclusion? Surprisingly, this is not the case. The cosmic background radiation -- the strongest ally -- would assume the role of "mean cosmic temperature" in the sense of Assis [6]. The also observed large-scale fluctuations in the WMAP would reflect a giant honeycomb structure that lies beyond the range of current telescopes (although some infrared and x-ray sources may already be pointing the way). The three other major pillars - primordial nucleosynthesis, inflation and accelerated expansion - would have to wait in line until the gross features have been straightened out. The third (large-distance dimming) may, by the way, prove reducible to Peebles' little-known (1+z)--4 formula [7], cf. [8].
But how about the riddles newly imported by a modern Brunian cosmos? First, in the absence of a far-from-equilibrium big bang, the persistent far-from-equilibrium state of the observable universe becomes incomprehensible. A gravitational effect partially anticipated by Einstein in 1912 [9] may possibly solve the mystery: Any particle in rectilinear motion inside a Newtonian (or Einsteinian) void enjoys a forward acceleration [10], cf. [11]. If this is so, gravitational energy gets "recycled" into kinetic energy in a Carnot-like manner. The same mechanism, by the way, could explain - jointly with Hawking radiation [12] - the second major new riddle that arises: the empirical "non-devouredness" of almost all matter by age-old black holes.
The main asset of a classical explanation of cosmological redshift, when held against the backdrop of the standard model, seems to lie in the fact that it introduces no hypotheses. lt only uses facts that are implicit in classical (post-Newtonian) mechanics and special and general relativity anyhow. lts predictions are irrefutable once their size has been correctly determined. What is surprising is only how many accepted hypotheses suddenly lose their hard-won plausibility.
Nevertheless it would be nice to have direct evidence as well. Very faint distant x-ray point sources appear to possess redshifts in excess of 30. This is because, on the one hand, the sensitivity ofx-ray telescopes is presently 1000 times greater than that of light telescopes [13]
- so that they can look 30 times (squareroot of 1000) deeper into space in principle - and, on the other, x-ray point sources continue to pop up at the lowest brightnesses [13]. This empirically suggested, two-tiered conclusion is incompatible with the big bang scenario (which leaves no room for redshifts beyond about 10 for massive objects). lt is about tobe decided by direct redshi:ft measurements in progress [13]. A hard - if weaker - fact is the recent optical discovery of strongly redshifted old galaxies 12 billion light years away, which has put cosmology into a full-fledged crisis [14,15]. While almost any way out appears acceptable at the time being, the above explanatory scenario was arrived at independently.
To conclude, the classical-mechanical finding of Fermi deceleration has upset the decades­ old belief that only a relativistic mechanism can account for the Rubble law. By coincidence, an empirical crisis holds cosmology in its grip in which fiddling with the usual culprits (like the star formation rate in young galaxies) seems insufficient to rescue the big bang model. In
,.:;uch a situation, even an at first sight alien, chaos-borne ray of light can acquire a warm glow.
Acknowledgments
I thank Christophe Letellier, Heinrich Kuypers, Dieter Fröhlich, Normann Kleiner, Peter Weibel, Erwin Wendling, Hans Diebner and Florian Grond for discussions. For J.O.R.
References
[1] O.E. Rossler, D. Fröhlich and N. Kleiner, Time-symmetric Hubble-like law: Light rays grazing randomly moving galaxies show distance-proportional redshift. Z. Naturforsch. 58 . 807-809 (2003).
[2] O.E. Rossler, Cosmic shear's temporal fluctuations generate a distance-proportional redshift in both time directions: Minibang theory. Chaos, Solitons & Fractals 12, 1335- 1338 (2004).
[3] A. Loskutov, A.B. Ryabov and L.G Akinshin, Analysis of billiards with time-dependent boundaries. Facta Universitatis Series Mechanics, Automatic Control and Robotics 11, 99- 116 (2001).
[4] B.B. Mandelbrot, CR. Acad. Sci. Paris A 280, 618 (1975).
[5] M. Seldner and P.J.E. Peebles, Astrophysical J 215, 703 (1977).
[6] A.K.T. Assis, "Relational Mechamics." Montreal: Apeiron 1999.
[7] P.J.E. Peebles, Principles of Physical Cosmology. Princeton University Press 1993, p. 226.
[8] O.E. Rossler, "Darkness intensified: Existence of a nonlinear threshold in redshift­ induced dimming." Z. Naturforsch. 54, 453-454 (1999).
[9] A. Einstein, Does there exist a gravitational effect analogous to electrodynamic induction?
"Collected Papers," English Translation edition, Vol. 4, pp. 126-129. Princeton University
Press 1996.
[10] O.E. Rossler, A morphogenetic instability in gravitation. Physica D 2004 (invited paper submitted).
[11] The term "Fermi acceleration" was already reserved by Loskutov et al. [3] for a different mechanism (the heating-up of billiards subject to repetitive head-on collisions with moving boundaries). Thus, a new term (“Einstein acceleration”?) will be needed for the present mechanism which has nothing to do with billiards and, by the way, does not extend to light, provided it is going to be confirmed.
[12] S.W. Hawking, Particle creation by black holes. Commun. Math. Phys. 33, 323 (1973).
[13] R. Giacconi, Kepler lecture, held at the University of Tübingen, July 2003.
[14] J.-M. Bonnet-Bidaud, Le big bang face à ses contradictions, Ciel&espace No. 412, 42- 44, September 2004.
[15] Editorial: Mature galaxies in young universe at odds with theory, Scientific American online, September 2004.
Remark added in 2020: Since this paper was written in 2004, Cryodynamics – explaining cosmology causally for good – got discovered; so this text remains just a step on the road.
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Is that has an effect on the biological life
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Wonderful question and interesting discussions.🌷🌷🌷
Fondest regards
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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 you just attacked the logical fallacy of "appeal to autority" and cite your own book in the same comment? It's not funny, but you make me laugh XD
"Astrophysics is a fabbrication of non-sense" is not satire, it's just you offending the work of hundreds of men and women; also satire is not a way of comunication in science.
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If the Earth going through space would be close to a black hole, it would be gone to the center of it. Perhaps it is surrounded by low-density air
My questions are:
1. Could exist a black hole there without eating Earth surrounded perhaps by vacuum?
2. If it is possible that the black hole generates a lot of energy in the out border of the event horizon that could explain that the Earth heating is about twice the received sun power?
3. If it could explain the Earth magnetic field
4. It's mass
5. How to detect it
6. If it is true, perhaps earth temperature is higher than several million years before. It is known what was the Earth temperature then?
I make these questions because I am worried about the danger of generating a stable black hole in a scientific test. If one of them were created, it would go to the center of the Earth eating earth generating a thin tunnel.
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I agree with dear Joachim Pimiskern
If we recall the TOKOMAK project, then a black hole can be artificially created. Skeptics see this end of the world.
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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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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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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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- When calculating ephemeris in the most accurate models of EPM and in some DE models, only miserable corrections are obtained from the PPN formalism. The Newtonian gravitation remains in the basement of celestial mechanics and of the GR. To my point of view, and stem from the fact, that geodetic lines in the presence of masses get bent, the Newton’s gravitation law suffers from a fundamental flaw due to violation of the inverse square law, underlying it. Let's try to go down from generalizations to specifics.
For example, discussing the modification of the law of Newton, I will argue that the mass is not an invariant, and the APPARENT gravitational mass depends on the distance to the observer Ma = M (1+ KR), where, for particular body, K = const. To verify the validity of the modified law, one will have to a) recalculate the masses of all celestial bodies in accordance with modified law, and b) get the Shapiro amendment, which will also depend on the (apparent) mass. As a result, using appropriate Shapiro delay values, we may get confirmation of the modified law.
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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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To ensure prosperity without destroying ourselves.
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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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There is much in your reply that starts ' The simple case would be ...' which is wrong and I recommend Feynman's lectures as a good starting point.
a) The electrical potential of an object in a system is not the same as the gravitational potential in a system.
b) ' Redshift is therefore caused by our potential falling. '
No. That is empirically not true. If I charge a lamp, its spectrum does not change one iota.
I can generate quite large Doppler shifts in a laboratory from a *neutral* gas by simply warming it.
I think that I'll step away from this conversation. Thanks for the replies.
<Feynman, or any similar introductory physics text: Kip for Electrostatics served me well, with Flowers and Mendoza for basic properties of matter>
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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,
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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No
According to the Criteria for scientific method and Occam's razor:
Criteria for scientific method:
(i). The model must fit the data and agree with observations.
(ii). The model must make predictions that allow it to be tested (falsifiable).
(iii). The model should be aesthetically pleasing
(Occam's razor: "If you have two theories that both explain the observed facts, then you should use the simplest with the fewest assumptions).
Dark Matter is an additional assumption. It would be better if we explained the flat rotation curve without invoking Dark Matter.
See: The Hyperbolic Universe Does Not Need Dark Matter
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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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