The universe refers to the cosmos; all of space-time and that which exists as part of it. Alternatively, it can refer to the observable universe, which only contains the part we can see. Questions tagged with this should ask about physics at scales the size of the universe or specific properties of ...

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1answer
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Curvature of the Universe imaginary?

If the curvature of the universe is zero, then $$Ω = 1$$ and the Pythagorean Theorem is correct. If instead $$Ω> 1$$ there will be a positive curvature, and if $$Ω <1$$ there will be a negative ...
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1answer
391 views

Are We Living in a Simulated Universe? [closed]

If the universe is just a Matrix- like simulation, how could we ever know? Physicist Silas Beane of the University of Bonn, Germany, thinks he has the answer!. His paper “Constraints on the Universe ...
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2answers
2k views

The meaning of multiverse

A) I am intrigued by the multiverse theory as mentioned in Stephen Hawking's new book, "The Grand Design". According to his theory, one can have different 'universes' in one ultimate existence, a ...
4
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0answers
239 views

Conservation of Energy in the Universe [duplicate]

Possible Duplicate: Is energy really conserved? Why can’t energy be created or destroyed? One of the laws of the universe that dazzles me the most is the law of conservation of energy. I ...
4
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1answer
449 views

Does the universe obey the holographic principle due to Stokes' theorem?

Does the universe obey the holographic principle due to Stokes' theorem? \begin{equation} \int\limits_{\partial\Omega}\omega = \int\limits_{\Omega}\mathrm{d}\omega. \end{equation} Can this ...
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1answer
94 views

All significant objects in the universe?

Taking it to the bottom of layman's terms, what would be the shortlist of significant things in the universe? A list I could think of myself would put Energy (at whatever wavelength travelling ...
16
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2answers
3k views

Why is oxygen the third most abundant element?

I was reading the article Oxygen finally spotted in space today in which it stated Oxygen is the third most abundant element in the cosmos, after hydrogen and helium. Why would oxygen take ...
0
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1answer
1k views

How does an inflationary universe solve the Flatness Problem, Horizon Problem and Monopole Problem? [duplicate]

Possible Duplicate: What is the evidence for Inflation of the early universe? I am reading some public science books on inflationary universe, e.g. The Inflationary Universe by A. Guth. ...
1
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1answer
351 views

Crucial Misconceptions about The Universe [closed]

So I am piecing together a school project on the numerous misconceptions of the universe, which I plan to "provide proof against them" with information from various sources (one of the main ones will ...
3
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2answers
360 views

(Co)homology of the universe

In this post let $U$ be the universe considered as a manifold. From what I gather we don't really have any firm evidence whether the universe is closed or open. The evidence seems to point towards it ...
11
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2answers
610 views

Is spacetime simply connected?

As I've stated in a prior question of mine, I am a mathematician with very little knowledge of Physics, and I ask here things I'm curious about/things that will help me learn. This falls into the ...
0
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4answers
1k views

Atoms pop out of nothing/vacuum/pre-big-bang?

I saw a great documentary last night about 'nothing'. It's about vacuums, and how if you have a total vacuum atoms will pop out of nowhere! Pretty crazy stuff. Atoms literally coming out of ...
2
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1answer
172 views

Fractal Cosmology and Misner's Chaotic Cosmology

I have a question pertaining to the ideas behind the considered homogeneity and isotropic nature of the universe (at a grand scale) versus the theory of a chaotic and anisotropy structure of the ...
18
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5answers
4k views

Does red shift evidence necessarily imply that the universe started from a singularity?

We are taught that the universe began as a singularity - an infinitely small and infinitely dense point. At the beginning of time there was a 'Big Bang' or, more accurately, 'Inflation'. The main ...
2
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2answers
283 views
2
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2answers
1k views

If randomness doesn't exist, how come the universe isn't a perfect sphere with predictable distribution of matter?

I'm presuming that the scientific community pretty much agrees that randomness doesn't exits, and that everything has a cause. Please correct me if I'm wrong, I've heard of quantum mechanics, but as ...
5
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2answers
295 views

What really is Spacetime?

What is a good definition on Space, Time and the most specific topic "Spacetime"? Because someone told me that spacetime is the foundation of the entire universe? And also, Is it possible to create ...
0
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0answers
59 views

Energy can't be created or destoryed? [duplicate]

Possible Duplicate: Conservation law of energy and Big Bang? If energy can't be created or destroyed then how did the big bang create energy? and if energy can't be created then does that ...
6
votes
3answers
653 views

Is the cosmic horizon related to the Big Bang event?

The Universe expands according to the Hubble's law: velocity is proportional to distance. There must be some distance, therefore, at which the velocity reaches the speed of light. This defines the ...
3
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1answer
146 views

What would happen in the final days of the universe?

I would like to know the stages of how the universe would end and what would happen and what the possible scenarios are. I understand that eventually all the stars would burn out and that would ...
2
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1answer
89 views

Why is that the space-time associated with the Earth is not shrinking?

If we apply the Friedmann Lemaître equation to the Universe, we find a critical density $\rho_c$ : if the actual density $\rho$ is under it, the Universe will continue to expand, if it is higher than ...
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2answers
111 views

Causal reconnection

Can causally disconnected regions join up again? For example the universe is expanding faster than light creating cosmological horizon, but what if something causes the expansion to slow down and ...
1
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1answer
1k views

is gravity always the weakest force [duplicate]

Possible Duplicate: What does it mean to say “Gravity is the weakest of the forces”? Strongest force in nature It is usually taught that the gravitational force is the weakest ...
3
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1answer
304 views

Total momentum of the Universe

What is the total momentum of the whole Universe in reference to the point in space where the Big Bang took place? According to my reasoning (and a bit elementary knowledge) it should be exactly ...
2
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2answers
853 views

Maximum Possible Information in the universe?

I remember hearing about this in one of the programs in discovery science. The physicist claimed that the maximum possible information in the universe is (10)^(10^123) whereas the maximum possible ...
2
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2answers
2k views

What is the difference between parallel universe and multiverse?

What is the difference between parallel universe and multiverse? Is it parallel universe or universes?
3
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4answers
969 views

As the universe expands, why do some things stretch but not others?

I got into watching a video on Olbers' Paradox a few days ago, and from there read about the origins of the universe, its expansion, and so on... it's always fascinated me, but now something about it ...
3
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1answer
891 views

Is the universe linear? If so, why?

Simple question, I'm trying to build a quantum memory system that utilizes the superposition principle to model specific phenomenon I am trying to predict, anyways, my question is this. Is the ...
3
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1answer
127 views

Does cosmic expansion imply the possibility of the universe splitting in half; multiple big-crunches?

There is an event horizon where cosmic expansion leads to superluminal recession speeds for sufficiently distant objects -- the Hubble Volume. 1) Does matter beyond the event horizon affect us ...
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6answers
1k views

What are the most realistic ways of high speed space propulsion?

Liquid and solid chemical fuels in rockets are very expensive and inefficient. I have heard of solar sails but what are the most realistic space travel fuels that will be used in the future to get ...
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1answer
565 views

parallel universe- are there an infinite amount of universes?

Parallel universe: in every universe, you are presented with a different decision. Does that mean there are an infinite amount of parallel universes? I.e., if in one universe I choose to go left, I am ...
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1answer
167 views

Do wormhole exits require matter? If not, would they change the edge of the universe?

As a layperson who watches way too many theoretical physics and astronomy documentaries, I've seen the folded-piece-of-paper analogy of wormholes a bajillion times. Usually they explain that black ...
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1answer
369 views

How fast was the universe expanding during the inflationary period?

Compared to how fast it is expanding in the post-inflationary period (now)
2
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1answer
232 views

How early can scientists detect that a deadly asteroid will hit planet earth?

With the advancements in science and technology, how early can scientists of the world detect that a certain asteroid will hit planet earth and cause damage? Are there any impact avoidance strategies ...
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1answer
73 views

Does the movement of things in the universe will cease one day?

To start or change the movement, we need a force. This force, according to Newton's second law, is variation of quantity of motion from the object per unit of time.Therefore, if the variation does not ...
0
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0answers
34 views

What is the support for the suggestion that reality is a computer simulation? [duplicate]

Possible Duplicate: Does Quantum Physics really suggests this universe as a computer simulation? I know the title sounds far-fetched, but the idea was first brought to my attention by a ...
2
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1answer
226 views

Why is Hawking's No Boundary condition described in terms of an instanton if there's no tunneling?

Regarding his take about combining No Boundary proposal with inflation theory (Hawking and Turok), he talks about the "pea instanton". To my very limited understanding I thought instantons were only ...
1
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1answer
240 views

Are there any theories or suggestions for how the multiverse came into existence?

I've just seen a documentary about the multiverse. This provides an explanation for where the big bang came from. But it leaves me wondering: how did the multiverse come into existence? Because this ...
4
votes
2answers
311 views

How does the critical density decide the fate of the Universe?

Trying to teach myself cosmology. Given the Friedmann equation $$\left[\frac{1}{R}\frac{dR}{dt}\right]^{2}=\frac{8\pi G}{3}\rho-\frac{kc^{2}}{R^{2}}$$ and the critical density ...
4
votes
1answer
199 views

Very basic question about empty universe

I'm trying to understand the empty universe model. My first textbook (which doesn't cover the empty universe) gives the Friedmann equation as $$\left[\frac{1}{R}\frac{dR}{dt}\right]^{2}=\frac{8\pi ...
6
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3answers
731 views

Can we prove that the universe is finite or infinite? [duplicate]

If I say that the universe is finite, how can you say with certain that I am wrong?
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1answer
350 views

Does the universe follow a general physical and computational principle of evolution?

Evolution is a principle in biology, whereby organisms evolve their ability to replicate and multiply in numbers over successive generations. From a computational point of view, the organisms employ a ...
5
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1answer
1k views

Is the universe finite and discrete?

Is the universe finite, both in the sense of being a closed spacetime manifold, as viewed from the macro level, but also in the sense of being fully discrete and finite in all of its intricate quantum ...
14
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2answers
140 views

Is there evidence of a larger universe?

While mapping out the position, distance and movement of galaxies and quasars at the limits of the observable universe, have astronomers ever observed the motion of these object due to gravitational ...
4
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2answers
587 views

What is the inertial frame that explains the Foucault Pendulum?

I know that the Foucault pendulum rotation in relation to Earth is a proof that the object is inertial in relation to the distant stars. But what makes them more important than the Earth? Are they an ...
1
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1answer
168 views

What about the other side of the Black Hole

I was wondering if on the recieving end of a black hole can you see the photons being sucked in
3
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1answer
621 views

Universe Expansion as an absolute time reference

Why we call "constant" to the Hubble constant?, if the universe were really expanding then the Hubble "constant" should change, being variable, smaller and smaller..with "time". Other example/view ...
0
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1answer
199 views

Is it possible that portions of the universe are made of antimatter? [duplicate]

Possible Duplicate: Experimental observation of matter/antimatter in the universe I've heard a bit about the antimatter, matter inbalance. But I don't understand how it has been decided ...
10
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2answers
847 views

Do we have an idea about the amount of matter in the universe?

Do we consider the amount of matter in the universe to be "infinite"? Or do we have an idea about "how much" there is?
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0answers
217 views

Presence Of an Another Universe [duplicate]

Possible Duplicate: Experimental evidence for parallel universes Is there an universe similar to ours somewhere else, I mean I had heard from Einsteins theories that,actually when I am ...