Universe Definition and 1000 Threads

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Summary:: I would like clarification about universe expansion. Hello I would first like to see if my entry level understanding of how the expansion of the universe is obtained or measured. (In a very basic model or example) First: My current understanding is that one way the distance to...

When we say the universe is "flat," do we mean: 1) If you could hypothetically "zoom" out to the edge of the universe it would appear roughly as a flat like a sheet of paper with local fluctuations / bumps to indicate the presence of matter. 2) If we draw 2 parallel lines from 1 location they...

I was discussing a problem related to Einstein's universe model. As we all know its an unstable equilibrium. So a small fluctuation in the density would result in an either expanding or contracting universe. However, I read that "There are static and stable solutions in Newtonian gravity...

The expansion of space is about 68 km/s/Mpc, or 0.00002 km/s/light year. The radius of the sun is about 700000 km. Thus, initially ignoring additional forces, the change in radius of the sun due to the expansion of space is about 1.5*10^-9 m/sec, or 5 cm/year. I assume that this expansion is...

https://www.google.ca/amp/s/phys.org/news/2020-02-astronomers-biggest-explosion-history-universe.amp

I’ve read many Legends and Canon Star Wars books and I always take away stuff on their limits of technology and science. Over the years; here are some things they said science can’t do. 1.) Cybernetic liver- In Lost Stars, it was said Ciena’s liver could not be replaced as it was one of the...

I am trying to derive the equation for a case, where we have a dust(zero-pressure) in an expanding universe. There are 4 equations but I think exercising on one of them would be helpful for me. I am trying to derive the equation for a case, where we have a dust(zero-pressure) in an expanding...

I'm quoting from Wikipedia the article about GN-z11 (the oldest and most distant known galaxy): "At first glance, the distance of 32 billion light-years (9.8 billion parsecs) might seem impossibly far away in a Universe that is only 13.8 billion (short scale) years old, where a light-year is the...

If early galaxies are already dead and we see them then we seem to be in an age where we are heading for a dead Universe, in my opinion what do you all think? https://m.phys.org/news/2020-02-astronomers-unusual-monster-galaxy-early.html [Post edited slightly by a Mentor]

http://astronomy.swin.edu.au/cosmos/B/Big+Bang D (density) = m/V At t = 10^-47, D = 10^93 kg/cm ^3, r = 10^-57 meters, V = 4pi(r^3)/3 which is about (4/3)pi(10^-171)(meters^3) t = 10^-47 precedes the inflationary epoch at t = 10^-35, this is important since this implies all matter at the big...

I got a phrase from a book that Stephen Hawking and his daughter Lucy Hawking published in 2011. The book is "George and the Big Bang" which is a science fiction book prepared for children. I read a phrase on that book that interested me. It was: "Perhaps there are many universes, each with...

All the accounts which I have read (and which are accessible to my limited knowledge of General Relativity and its mathematics) on the holographic principle says vaguely that the AdS/CFT correspondence is very enlightening, but with the caveat that, well, we don't happen to live in an AdS space...

As object separate with a receding velocity proportional to the distance, it would seem appropriate to think that objects and space itself, which are located at a distance sufficiently far away (and beyond) to were recession velocities are large enough that Lorentz length contraction effects...

Okay, just for kicks, I was wondering how do you calculate the the rate of cooling of the universe? All I could think of is using the Ideal Gas Law from Thermodynamics: Ideal Gas Law: P V = n R T | V | volume P | pressure n | amount T | temperature R | molar gas constant (≈ 8.314 J/(mol K)) I...

do physicists and cosmologists really know how the universe will die?could there be a new Big Bang?

Hi, I'm only trying to understand the basic concept. Did the big bang give rise to both observable and non-observable universe? I have been through quite a few source and it seems like that the big bang was the cause of only observable universe and not of unobservable universe. Below I have...

Since acceleration due to Newton's law decreases as the inverse of distance, it becomes very weak at large distances. Our Sun was unable to pull in matter in the Oort cloud in over 4 billion years. Above about 0.11 light years, using modified Newtonian dynamics equations, gravity decreases by...

How did the universe come into being? Where did quantum fluctuations come from? How did it come out of nothing? Is there something that always exists?

I know this question doesn’t really make sense but the absurd enormity of the universe always made my head hurt. A single galaxy alone has more then enough stars to satisfy the curiosity of any sentient being. Why 2 trillion? It’s just insane. Why did nature have to create so many? The spaces...

is everything lawrence krauss said about the universe true?what does he think of parallel universes?

I hope that I am conveying what I see in my head clearly. I guess that I am visually imagining the 3 spatial dimensions projected on the 2d surface of a sphere and as that sphere expands that the increased distance between 2 points would happen what seems like at an accelerating rate because of...

My first question. I was taught in school about Big Bang as a theory of physics, so then if the entire content of our universe came out from one tiny point boundary over a finite span of time, would that mean the content was finite?

Does the CMBR contain the imprint of the entire expansion history of the universe or only of the last scattering ?

I read a news article about a recent study into the cmb which suggests that the universe is now been discovered to be closed and curved. Not seen anything here so am assuming it’s just another misinterpreted pop science piece. Anyone know what the article is talking about please? please see...

As a newbie, I'd welcome your input into this summary of mine. I want to establish some firm foundations (or as firm as possible). Seems like a good way of learning the basics... Our universe consists of fields and nothing else, i.e. quantum fields and the spacetime field (gravity). All fields...

Do we know? Do we have any idea? There seems to be 2 schools of thought. 1. The initial conditions can be almost any value with universes inflating with different laws of physics. This is the multiverse and string theory 10^500 false vacua view. 2. The initial conditions are more restrained...

Summary: Is it possible to tell the current average universe expansion rate i.e. acceleration of expansion in m/s^2 ? Is it possible to tell the current average universe expansion rate i.e. acceleration of expansion in m/s^2 ? If i say in relation to earth, does this make it easier to answer...

do parralel timelines have to run concurrently to our time? what I mean by this is basically if there is a version of me or you out there in a parralel universe right now in 1963 for example just living like normal or do all parralel timelines have to be in the same timeframe as us?

arXiv:1910.10739 [pdf, other] New Early Dark Energy Florian Niedermann, Martin S. Sloth Comments: 6 pages, 2 figures Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th) New measurements of the...

I am trying to prove that for a single component flat universe $$\frac{dz}{dt_0} = H_0(1 + z) - H_0(1 + z)^{\frac{3 + 3w}{2}}$$ For a single component flat universe, ##q = \frac{2}{3 + 3w}## ##a(t) = (t/t_0)^q## ##t_0 = qH_0^{-1}## ##1 + z = (t_0/t_e)^q## Now here is my approach...

Summary: Since L = T - V, and T equals the kinetic energy (KE) of a particle whose trajectory is to be calculated, how is KE defined since some of its motion will be due to the expanding universe? My understanding may well be wrong, but it is the following. if a particle is stationary at...

It has been reported [http://www.astro.yale.edu/larson/papers/SciAm04.pdf, https://www.scientificamerican.com/article/the-first-stars-in-the-un/] that scientists have observed spectra of radiation emitted by quasars that date from about 900 million years after the big bang. Others have observed...

If in the early Universe the matter density was density so large causing an intense gravity field, was the time at that epoch running much more slowly compared to the actual time according to the GR? If so then, would any reference frame in the early Universe see the light apparently traveling...

Hello. Wannabe sci-fi writer here with what may be a simpleton's question. From Google et al: "It took 380,000 years for electrons to be trapped in orbits around nuclei, forming the first atoms. These were mainly helium and hydrogen, which are still by far the most abundant elements in the...

Paul Dirac proposed a hypothesis called "Large Numbers Hypothesis" (https://en.wikipedia.org/wiki/Dirac_large_numbers_hypothesis), where he basically stated that, if he was correct, laws of physics would change with time. But what about fundamental laws and constants? (Not only 'effective'...

Quantum theory shows that every and all posibile states exist. As we get better at measuring our visible and detectable universe, it becomes ever clearer that we are missing so much. My question is: If infinity is infinite, then that must apply to scale, could you have infinite multiverses in...

So first of all ,we all agree that Universe exists and it is not totally chaotic , it seems to have some laws that govern its behavior. Would we ever be able to fully discover and understand the true laws of the universe. Or human intelligence is limited (the way the human brain is constructed...

Summary: The universe is expanding, so at one point in the past it must have been all concentrated into a single point. But is this really an accurate observation? Hi, This is my second probably naive question that's been on my mind as a lay-scientist for a long time (the other will hopefully...

suppose the universe started shrinking. because the density vs mass is a 1/M^2 factor, density can be made arbitrarily small given high enough mass. so it's not hard for all the mass in the universe to quickly reach black hole density. when critical density of the universal is reached, what...

If so, do we have estimates of what that is. Also, if we have estimates of that, what will the final entropy of the universe be, in J/K?

According to physicist John Wheeler, the universe is part of a sequence of cycles of Big Bangs and Big Crunches, called cyclic or oscillatory universe model (https://en.m.wikipedia.org/wiki/Multiverse (Mentioned in "Classification schemes") According to this author, in each cycle, the laws of...

The rates I've come across are 67, 71 and 74. Obviously it's not 74 as it was just announced. Is it one of these other numbers, something else? I'm only asking out of curiosity.

A basic question... The further a galaxy is from ours, the more redshift, the faster it is moving away from us. This is taken as a sign the universe is expanding at ever increasing rate. Yet... As we look farther out into space, we are also looking back in time. If the farther we look back in...

The Friedman Equations is based on the cosmological principle, which states that the universe at sufficiently large scale is homogeneous and isotropic. But what if, as an hypothesis, the universe was anisotropic and the clustering of masses are aligned to an arbitrary axis (axial pole), how...

Disclaimer: I am parroting the information in this from articles that I've read. This post is to try to get a better understanding of what they are talking about and if any of it is relevant. I came across an article regarding the Big Bang while looking into the current rate of universe...

I pick up half information on some things, so please straighten me out on this. My understanding is that gravity is an emergent property of expanding space time. So presumably if space time shrinks in the very distant future then, if that were to happen, gravity would become a repulsive force...

Summary: Was our universe once connected to another universe many billions of years ago? I read about a theory which states that our universe used to be connected to another universe which somehow split off from it many billions of years ago. Is there any corroborating evidence to support this?

Does any parallel universe theory include the concept that in at least one of the parallel universes, there is no option for there being parallel universes? If so, how could that unique universe not kill the entire theory?

Recently a news article stated objects found in the universe have different ages, could it be that our universe is inside an already existing universe and that is why it is able to expand so easily.