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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What proof do we have that space is expanding? [duplicate]

how can we really say that space is expanding when we cannot see the distant galaxies forming nor are the planets nearby newly formed, nor is anything expanding in size nor are we going far away? ...
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31 views

if gravity travelled faster than light, what would the implications be? [on hold]

I know that some weird stuff might take effect in the long term outside of the observable universe affecting us and I do have a lot of ambitious, intuitive guesses based on my qualitative ...
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41 views

What is the status of the Church Turing Deutsch principle? [on hold]

The Church Turing Deutsch principle states that: every finitely realizable physical system can be perfectly simulated by a universal model computing machine operating by finite means. According ...
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30 views

How can we make use of wormholes? [closed]

Some people say blackholes are wormholes which could be a shortcut through spacetime. This is great, because if its true we can travel deep into the universe. However, everyone knows the gravity in a ...
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2answers
41 views

Why is the ratio dark matter / normal matter bigger today than in the past? Is it the dark matter that increased or the normal matter that decreased?

These two pie charts clearly show that the ratio dark matter / normal matter is bigger today than it was in the past. But why? How is it possible? And does it mean that the amount of dark matter ...
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1answer
71 views

Traveling faster than the universe is expanding?

I was thinking, if the universe is space and time expanding, lets say in 3D (like a sphere). And it is doing that in a constant or not constant speed, there is a debate about that, never mind that but ...
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1answer
45 views

How can gravitational energy cancel out the rest energy of mass in the universe [duplicate]

I've heard that some physicists think that the net energy of the universe is zero. For this to happen, I would assume that the negative gravitational energy of a body ought to cancel out its rest ...
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65 views

Is there evidence that the universe truly is the entirety of “everything”? [closed]

This is a question that has popped in my head recently. Do we have any verifiable proof that the "known" universe truly is everything that is out there? I'm not talking about the multiverse theory ...
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3answers
308 views

What does the accelerating expansion of the universe mean about its end?

So we know that the expansion of the universe is accelerating.When we thought that the expansion of the universe was slowing down,we predicted that it would reach a plateaux and maybe reverse the ...
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2answers
61 views

We stretch as the universe does [duplicate]

Here's an idea I thought about; more of a thought experiment than anything: The universe is essentially the same as the universe 14 billion years ago, just stretched. However, all matter stretches ...
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4answers
757 views

Can a perfectly mathematically describable universe exist in a multiverse?

Assuming inter-universal (see here) travel is possible, can a perfectly mathematically describable universe exist inside a multiverse? If it could, would that mean that the multiverse is ...
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1answer
75 views

Is it impossible to practically predict the future?

For the sake of curiosity, let us postulate a universe that can be completely described by mathematics. Let us further postulate, that humankind has fully discovered all the fundamental laws of ...
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21 views

Relation between black hole mass and size applied to observable universe [duplicate]

If I apply the relations given in http://xaonon.dyndns.org/hawking/hrcalc.js and http://www0.arch.cuhk.edu.hk/~hall/ag/sw/SpinCalc/SpinCalc.htm to the values for the mass of the observable universe ...
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1answer
61 views

Test to determine if universe is infinite or not

Currently it is not known whether the universe is finite or infinite. Is there any test that can be performed (theoretically) to know whether the universe is infinite or not? I'm still in high ...
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2answers
96 views

Where did energy come from?

So it is my understanding that before the big bang there was a very small point that held all of the matter in the universe. My question is what form did energy of the universe take on when it was in ...
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2answers
37 views

Is every aspect (fundamental forces, periodic table) of an antimatter universe exactly the same, except the fact that it's all antimatter?

Are all the constants (Boltzmann's, gravitational, $c$) the same? Would elements react differently? Would it look the same?
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1answer
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Why haven't we seen the big bang?

The Andromeda galaxy is 2,538,000 light years away, so if we view Andromeda from a telescope, we see Andromeda how it was 2,538,000 years ago. Now the diameter of the visible universe is 92 billion ...
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1answer
77 views

When they say the universe was the size of a baseball about a billion billion billion billionth of a second

after the big bang. Does that means the observable universe was the size of a baseball, or does it mean the entire universe? I'm guessing it means the observable universe - as we really don't ...
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1answer
25 views

cosmological red shift significance in terms of success of gr

So from a killing tensor the FRW metric is known to possess, for a massless particle we find the well known result that as the universe expands the frequency of the photons decreases . But , what ...
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2answers
59 views

Why should I believe that matter does not expand along with the space between it [duplicate]

This question has been asked before under other guises. I am not a scientific profesional however i have some schooling in pyhsics and mathematics and have a keen interest in these subjects. It seems ...
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3answers
335 views

Where is all the Dark Matter? Theoretical Question

In my Physics Class we had to look into possible areas where Dark Matter could be "hiding." Such as Black Holes and so on. Dark matter really can be "seen" through its gravitational effects, and we ...
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1answer
20 views

Single fundamental force at Planck epoch?

It is hypothese that after big bang when universe is a Planck time old, the 4 known fundamental forces used to be equal in strength or perhaps there existed single fundamental force before splitting ...
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4answers
2k views

Why is the singularity of the Big Bang not considered to be the center of the Universe? [duplicate]

If the universe is expanding, then at some time in the past, it must have started from a single point but why this point is not the center of the Universe. Just like the singularity of black holes is ...
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1answer
65 views

Does universe calculate? [closed]

This is probably totally naive (philosophical?) question. I am not mathematician nor physicist so maybe it is quite dumb question too. IF universe does calculate, how does it cope with numbers like ...
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1answer
72 views

Are we really sure that the whole universe is expanding?

Haven't we thought about the possibility of only a region of the universe is expanding? What about space is expanding in this region and space is compressed in another region, that satisfies the ...
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1answer
66 views

The actual space curvature

What is the curvature of our physical space, according to the latest experimental data? I've found it somewhat difficult to find a definitive answer to the question, because the spacetime curvature ...
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67 views

How many electrons are there in the universe?

Someone on io9 estimated there were about 10^80 electrons in the universe, but I want to ask the Stack Exchange physics community.
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3answers
144 views

Can universe or anything be simulated with absolute accuracy? [duplicate]

In a simulation everything is known which makes any apparent random event a pre-calculated event. Taking that into account is it possible to simulate the universe with absolute accuracy in a way that ...
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1answer
110 views

How can the Schwarzschild radius of the universe be 13.7 billion light years?

So i was reading about Schwarzschild radius on Wiki and I found a interesting thing written there link. It says that the S. radius of the universe is as big as the size of the universe? How is this ...
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0answers
22 views

Why is the total energy of current universe conserved? [duplicate]

I began to think about this problem a long time ago and also asked some classmates as well, but none of them can give me a creative solution. I actually developed an original theory that our ...
3
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1answer
55 views

Where else is there fire?

Apart from on Earth, where else does fire occur in the universe? I'd hazard a guess that it is quite rare for oxidation to occur naturally, could someone elaborate on this?
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21 views

Calculate Total Energy Of Universe [duplicate]

Physicist using $mc^2$ to calculate positive energy and $-MmG/R$ to calculate negative energy to calculate total nergy of the universe but I heard that one of them is relativly invariant and other ...
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2answers
73 views

Allowable spacetime deformations [closed]

What deformations are possible with spacetime? By 'deformation' I am referring to the kind of change in spacetime caused by the presence of a mass which deforms spacetime sufficiently to deflect ...
2
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2answers
101 views

How does a particular galaxy's apparent recessional velocity CHANGE as the universe expands?

By this I mean will the light from distant galaxies continue to show red shift (i.e. if you look at light from a particular galaxy now and in 10000 years time, the spectra will have been shifted ...
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1answer
60 views

Is the center of the universe in another dimension?

If we live in a four dimensional world and when we try to find the center of the universe (where the big bang occured) we found that there is no apparent center, could that means that the big bang ...
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0answers
41 views

Total Mass in Universe [duplicate]

Currently (2015), what is the total mass of the universe? How can we say with mathematical certainty that 69% is dark energy; 25% is dark matter; 5% is atomic matter; and 1% is neutrino, photon, and ...
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2answers
71 views

What would happen after the big crunch?

What is the aftermath of the big crunch?
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0answers
20 views

Higher dimension world possibility [duplicate]

Could it be possible that all of the unexplained phenomena (like uncertainty) in our 4D world might be originated from a higher dimension universe? If so, then of course we'll never observe the ...
2
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2answers
156 views

Is the universe 5 dimensional space-time or 4?

we've been told that in General Relativity (GR), matter tells space how to curve and space tells matter how to move. But my question is, if 3 dimensional space was curved by matter then it should be ...
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1answer
27 views

Will all the mass collapse in one place?

Will the stars, planets and everything in the universe collapse due to the gravity? Or does the constant expansion of the universe break that idea ? What will happen with the energy?
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62 views

Looking for more information about these two hypotheses

Big Lurch - This was one I read about in a special issue of Scientific American from 2014. It was explained as The Big Lurch is a theoretical scientific model suggested as one of the ...
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1answer
51 views

Are all galaxies we see really our Milky Way? Any possibility?

There is a possibility for our universe to be the surface volume of a (higher-dimensional) hyperspace. So if this possibility is true,then is there also a possibility that the other galaxies we see ...
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1answer
53 views

Given an initial push, is work done on an object infinite in a hypothetical empty universe?

Consider a hypothetical empty universe containing a single object. Given an initial push, will the work done by the forever moving object be infinite?
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28 views

Is not the idea of a continuous universe and finite information density mutually exclusive?

As far as I understand, the universe is not divided into discrete units, but rather its continuous. This seems backed up by a quick search: Does the Planck scale imply that spacetime is discrete? ...
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0answers
126 views

What evidence is there of a universe older than 13.8 billion years

I've read an analogy that finding iron-rich galaxies just 900 years after the Big Bang is like finding an old man in a crib in a nursery. We just recently found a supermassive black hole 12 billion ...
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2answers
79 views

Negative energy of universe

According to a little I have understood whatever we see in the universe is its postive energy and there is so an equal negative energy. Is this Negative energy the Dark energy? which is responsible ...
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2answers
163 views

Can a sufficiently large black hole be singularity-free?

This came to me after reading that a black-hole that has the mass of the observable universe will also have an event horizon that covers the observable universe. Since the definition of a black hole ...
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1answer
53 views

Even the universe is infinite, it could keep expanding? [closed]

the study showed Cantor, that there are infinite types, the universe would be expanding as well as the possibility of Stephen Hawking. http://phys.org/news/2015-02-big-quantum-equation-universe.html
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1answer
78 views

How do we know the expansion of the universe is “of space” and not “in space” or “into space” or another less intuitive arrangement?

How do we know the expansion of the universe is "of space" and not "in space" or "into space" or another less intuitive arrangement? For example, what implicit and explicit assumptions underlie the ...
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3answers
140 views

Is it valid to apply Einstein's Relativity to scenarios involving expansion of space?

IIs it valid to apply Einstein's Relativity to scenarios involving expansion of space? For a practical example of this: Is it legitimate to speak of distant red-shift galaxies as experiencing time ...