Astronomy and Cosmology

If the stars of the constellations are stationary, then is the Sun also stationary. How can the Sun be in motion, if the stars of the constellations are fixed ("fixed stars").

does our galaxy have a dark matter component that has been estimated as to amount and distribution as of yet?

I don't think General Relativity predicted either ,did it? So ,when thinking about them is GR of any import? For example ,with inflation it occured to me that with the enormous activity occurring it might be represented as space stretching and time stretching less(or contracting?) But then I thought "Maybe GR has nothing to do with this?"

If I went for an afternoon stroll on Titan, will I be able to see Saturn through the clouds and do the clouds ever clear sufficiently to give sunny days?

From what I know, dark energy is the posited energy driving cosmic expansion. This seems to imply cosmic expansion is work (requiring energy), but then I was told cosmic expansion is the space stretching and space has no mass. How is work being done in cosmic expansion when no mass in involved, a work that requires dark energy?

According to my calculations Mars having a Scale Height of 11.1km means that we are only 30km away from reaching 0.7 bars of air pressure from the Northern Basin or Hellas Planitia. Can we deflect a comet or more to the same spot on such an elevation on Mars to excavate 30km? Then the water from the comet can produce a liquid water lake for us since it will be within the Armstrong Limit now and we can introduce algae and plant life in cheap greenhouses to slowly terraform Mars as a micro climate via photosynthesis to convert the CO2 to O2 slowly. The comet the size of Hailey’s would also contribute 1% to the Martian atmosphere with gas. While negilgible on it’s own if thi…

As seen through the other end of the telescope. Any offers ?

I've not seen this question posed before, and I've approached the question from different perspectives yielding different answers. What is the difference in gravitational potential from here on Earth to zero potential (the hypothetical potential of an empty universe)? From a mathematical standpoint, it seems to be infinitely negative. The escape velocity from a 1D infinite length rod drops off at 1/r, and so if gravity is X at the rod, it is 1/2x at twice the radius of the rod. The series ∑ 1/n does not converge. With a 2D infinite sheet, gravity does not fall off at all with distance, and the series ∑ n certainly does not converge. All these abstract cases ha…

How does the light from distant stars get to our eyes? Maybe it's just my misunderstanding, but the odds of seeing a distant star seem astronomically low. Here's my understanding of how it works. Please let me know if I've got anything wrong. The light emitted from stars are photons. Photons travel through space as waves. These waves are no different than the waves of any other particle described by the wave function of quantum mechanics. That is to say, they describe the locations where the particle is most likely to be if one attempted to measure their location. By the time a photon from a distant star reaches my eye, the wave spans a vast amount of space…

I don't understand in what sense there is an issue here.

Hello! The most of the living population of our planet can observe light and colors, right? But what was light before there was life in the universe? How can we look on the earlier universe when you couldnt feel, look or hear anything. Is it just like it was waiting till life would be created, or is it more complex than that and like the infinity just inconceivable for us?

My interest in Cosmology started back in the late 70's. However in the early 80's when Alllen Guth's first published his false vacuum inflation model accelerated that interest even further. That interest has been a primary focus of my studies ever since. Back then inflation often involved quantum tunnelling from a false vacuum state to a true vacuum state. These models typically had the energy density graph transitions as in a similar fashion to https://www.wolframalpha.com/input?i2d=true&i=plot+Power[x%2C2] thoough they would often include a higher potential of the same curve to represent the stable region of the higher potential false vacuum state. Those …

Hello everybody, Here I have some constructive research on my project which I have through my experiments on my YouTube channel, explaining how a near copper coin from 2010 gained a obvious visible appearance of carbon from my last experiment, supporting that my project works this is a lot to explain so please feel free to click the link and watch, how I did this process of turning a clean near copper coin into a apparent coat of accumulated carbon. YT link removed

I was reading some articles about dark energy and its possible equation of state. I stumbled upon this article https://arxiv.org/abs/1804.02987 which stated that "a dark energy field with w < -1 is a viable option", "phantom dark energy does not categorically have negative kinetic energy" and "kinetic energy is positive for w≳−1.22, which includes virtually all values of constant w allowed by cosmological data constraints". I'm a bit confused with negative and positive kinetic energy of dark energy, but all sources I've read have stated that Big Rip can happen due to a phantom dark energy field with a negative kinetic energy. Does it not happen if the field has w &gt…

According to the current model, an almost infinite amount of mass was compressed to a small dot, but inflation is granted the special privilege to separate mass that is more compressed than a black hole with a much stronger gravity in order to create galaxies with similar characteristics than the milky way in less than 300 million years (while the Milky Way makes 1-2 spins)? According to the Friedmann-Lemaitre-Robertson-Walker metric, the model is valid only on large scales (roughly the scale of galaxy clusters and above), so why are we making this huge exception for the tiny big bang? Why would inflation separate a huge black hole back then and not now, if dila…

Interesting in the following article it describes the reaction rate of Hydrogen as it drops out of thermal equilibrium. Using the temperature to redshift relation T=T0(1+z) or alternateIy the inverse of the scale factor a. I calculated the temperature of 4000 kelvin to z= 1492. The article evidently rounded this to z=5000, this corresponds to universe age 218,000 years old for the universe. The table also shows the reaction rate for higher and lower temperature values. https://iopscience.iop.org/article/10.3847/1538-4357/ab2d2f/pdf. This additionally tested the mathematics I was examining using a method by Juan Garcıa-Bellido. Details are in the…

Hello! Each [latex]m^2[/latex] of surface of Earth is receiving 1367 W (ignoring atmosphere influence). We know inverse-square law: [latex]P = \frac{P_0}{4*\pi*r^2}[/latex] After reversing it, we're receiving: [latex]P_0 = P*4*\pi*r^2[/latex] Distance to the Sun is approximately [latex]r = 150*10^9[/latex] meters. After plugging numbers we get: [latex]P_0 = 1367*4*\pi*(150*10^9)^2=3.8651*10^{26} W[/latex] As you can see this pretty much agree with wikipedia Sun page http://en.wikipedia.org/wiki/Sun (Luminosity on the right table) It's energy Sun is emitting every single second. One of possible fusion path is: …

Any fans of Anton Petrov? In his Youtube he says he found a study critical of the Kardashev Scale. I cannot find the paper. Anyone heard of this? This is about a qualitative approach to understanding levels of ETIs rather than the quantitative Kardashev Scale. Below is what I paraphrased from Anton's excellent video. "According to this study, advanced civilizations could be anywhere in the universe, our galaxy, even close to us. They would be indistinguishable from their natural environment, so we would not detect them. Super-intelligent alien life would look to us like ordinary matter. We would not know what to look for. We cannot imagine what we can discove…

Hello! So i have a question: The universe is expanding, meaning objects not close to eachother are moving away (making more space). Gravitivity of objects like the sun, never disappear in the universe. But at some space their attraction is barely perceptible. So if some time, every galaxy is so much away from each other, nothing pulls eachother anymore (there are only objects standing around in space). Would that mean the universe had no stability anymore? So will the universe colapse at some point? I´m not very educated in physics yet, so could somebody correct this assumption?

As a means of creating artificial gravity sci-fi authors and movies have often suggested using a centrifugal force in a rotating space station or spacecraft, as in 2001 A Space Odyssey However the idea apparrently fails to take note of the "Coriolis effect" which would cause immediate nausea and loss of balance, like motion sickness, unless the rotating radius were very large eg 1 mile+ Yet even Lord Nelson was seasick for several days after putting to sea, but would then gain his sea legs and be unaffected. Is it possible that the bodies of individuals like the crew of 2001's spacecraft Discovery One may adapt after a few days and get their "space legs" le…

Tell me, please, what are these space objects. I have an idea that these are black holes, but this answer seems pretty simple. Please also indicate the common feature of these objects.

Richard Dawkins is especially scathing of astrology, along with most scientists. But I wonder what scientists here think of this idea from the Hitch-Hikers Guide To The Galaxy about the Total Perspective Vortex; "The idea is that, if every atom of the universe is affected by every other atom of the universe, it is in theory possible to extrapolate the whole of creation—every Galaxy, every sun, every planet, their orbits, their composition, and their economic and social history from, say, one small piece of fairy cake." So if every atom of matter attracts every other particle of matter in the universe, it follows that there's a relationship between the attr…

hello i would like to ask if astrophotography can image through walls similar to terahertz and millimeter wave imaging. thanks very much.

Just a fun question: what state of energy/matter, could it be argued, that a gravitational singularity is in? I would say that, it broke down to the most fundamental form of energy. Could it be said that, it is an extremely exotic form of atom?

Looks like the NASA Dart mission test was a success. A couple of questions from this https://www.nasa.gov/planetarydefense/dart/dart-news If an asteroid was heading towards the Earth and we used a similar method to the above to change the trajectory is there a danger that this could cause any asteroid to hit the moon ? (Similar method, as if this can happen anytime, even 100 years from now we will have moved on technically but still need to do this. ) In which case, would we need to consider any impacts on Moon bases Is there a danger that any impact on the moon could cause debris from the Moon to hi the Earth, or any satellites in orbit ? …