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 exactly is expanding when they say universe is expanding? [duplicate]

We know that universe is expanding and galaxies are moving away from each other. Does this mean the galaxies are also expanding in itself and therefore I guess growing larger in volume? Depending on ...
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0answers
100 views

Are we travelling at a speed close to the light speed? [duplicate]

This is a question which has been puzzling me quite a while. There was a news report saying that the farthest galaxy spotted so far is at 13.3 billion light-years away, and it is said that the galaxy ...
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1answer
463 views

What is the geometry of our universe?

I have some questions about the notion of space in current cosmological theories. I have been trying to decipher a few papers written on this topic such as this one, but I keep running into some ...
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3answers
567 views

Can the big bang be “light turning into space” at the edge of the universe? [closed]

The theory I've recently come to postulates that: The volume of space filling the universe is finite and is constantly growing, thus the boundaries of the universe are constantly expanding. The ...
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2answers
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Physical laws prior the big bang (quantum fluctuations)

A theory among scientists says that quantum fluctuations caused the big bang and created the universe. This seems plausible to me. What I can't grasp yet is how a quantum fluctuation can even start ...
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2answers
515 views

How is it possible to come to a conclusion that Universe is a result of the Big Bang while we aren't able to observe the entire Universe?

-I'm not a religious person so this is not a denial. I'm just trying to understand the most fundamental topic about Universe. -I know the Big Bang cosmological model is not a law but it's a theory. ...
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0answers
96 views

Can universe be a closed manifold?

I had a question at MSE which gave a rise to another question. Maxwell equations can be written in form $$d\star F = J$$ Then by Stokes theorem we have $$ \int_U J = \int_U d \star F = ...
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2answers
152 views

Could the outer structure of the Universe be made from Antimatter?

Cern recently stated that antimatter may be repelled by matter, much like the opposite effect of Gravity. So is it possible that antimatter is actually repelled to the edges of the Universe to create ...
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7answers
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Does Quantum Physics really suggests this universe as a computer simulation? [closed]

I was reading about interesting article here which suggests that our universe is a big computer simulation and the proof of it is a Quantum Physics. I know quantum physics tries to provide some ...
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1answer
68 views

Astronomical measurements and data

For the sub-nuclear physics there is a database of the Particle Data Group, I was wondering if there was a similar on-line collection for astrophysics, such as energy absorption and emission spectra ...
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Correlation between speed, distance, mass, etc between a planet and a star (or moon and planet)?

While playing around with some little scripts, generating solar systems, I started to wonder about the correlation between the different objects. Up until now, distance, mass, size and speed are ...
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1answer
851 views

Is time slowing down and disappearing from the universe instead of the expansion of universe? [duplicate]

Are we fooled into thinking that expansion of the universe is accelerating, when in fact, time itself is slowing? Or if dark energy does exist?
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4answers
659 views

Are scientists missing the point with distant cosmic objects, or is it just me?

I was reading this article this morning: http://www.bbc.co.uk/news/science-environment-13539914 Scientists have discovered a gamma-ray burst whose light has taken 13.14 billion years to reach Earth. ...
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1answer
108 views

Universe with ZERO Fundamental Forces

Warning: I am not a physicist so please excuse my naivety! As you all know, physicists think that there exist four fundamental forces. Would a universe with zero fundamental forces be possible, at ...
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1answer
193 views

What is the wave length of the entire universe?

In quantum physics, particles are also waves. Larger particles have shorter wave lengths, and macroscopic objects have extremely short wave lengths so that the wave aspect can be ignored, and ...
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6answers
3k views

How many bits are needed to simulate the universe?

This is not the same as: How many bytes can the observable universe store? The Bekenstein bound tells us how many bits of data can be stored in a space. Using this value, we can determine the ...
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4answers
3k views

Infinite universe - Jumping to pointless conclusions

I watched an episode of thee BBC Horizon series titled 'To infinity and beyond'. In this program a number of respected physicists and mathematicians were talking about the nature of infinity and an ...
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2answers
159 views

Is it possible that universe might not be speeding up expansion?

I'm not sure but I was thinking of galaxies shrinking with time while still moving apart from each other at almost a constant speed or less (i.e: uniform/slightly decelerating expansion). This may ...
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2answers
923 views

Are all points in the universe connected?

Is it true that every point in the universe is connected or could be so theoretically? If so how is this mediated? Is it through the quantum nature of the fabric of space or is it through the ...
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5answers
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Does the amount of gravitational potential energy in the universe increase as it expands?

It seems to me that extra gravitational potential energy is created as the universe expands and the distance between massive objects such as galaxy clusters increases; this implies that energy is not ...
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0answers
54 views

Has Time in the Universe been found to be Discrete or Continuous? [duplicate]

I have a question, has the Universe been found to come in Discrete Quantum, like Quantum Physics or is it Continuous in Nature? I was wondering if time was like a Continuum, like the fluid in a soft ...
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0answers
185 views

Do we expect that the universe is simply-connected? [duplicate]

I heard recently that the universe is expected to be essentially flat. If this is true, I believe this means (by the 3d Poincare conjecture) that the universe cannot be simply-connected, since the ...
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2answers
279 views

A question to the theory of multiverse

Guys I couldn't catch a point of multiverse theory.. Theory: If space-time goes on forever, then it must start repeating at some point, because there are a finite number of ways particles can be ...
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3answers
197 views

Acceleration in the rate of expanansion of the universe due to weakening gravity?

Could the acceleration in the rate of expansion of the universe be due to the weakening of gravitational forces, as the distance between objects continues to increase?
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1answer
56 views

Is dark matter expanding the universe, and creating the structures within it?

If dark matter repelled other dark matter, as well as regular matter(atomic or celestial), and regular matter were repelled by other regular matter "less" than by the dark matter, would not this ...
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2answers
288 views

Is this a great flaw in big bang theory? [duplicate]

Einstein said that, Time & Space cannot exists without one another. Big bang says, time didn't exist before the big bang. So the Primordial ball referred in the Big Bang theory didn't had any ...
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1answer
417 views

What is the curvature of an empty universe?

My calculations tell me an empty universe has hyperbolic curvature. Is this correct? If it is, can anyone help me understand why this is intuitively?
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3answers
338 views

What is meant when it is said that the universe is homogeneous and isotropic?

It is sometimes said that the universe is homogeneous and isotropic. What is meant by each of these descriptions? Are they mutually exclusive, or does one require the other? And what implications rise ...
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1answer
161 views
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2answers
1k views

If the universe is 3D, how is space-time like a “fabric”? [duplicate]

I have been taught that space-time should be viewed as a fabric and that objects with a large gravitational influence indent that fabric. My question is, if the singularity of a black-hole punctures ...
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2answers
117 views

can we have a parallel earth made of dark matter?

In the sense that the two planets move together and has intelligent beings with their own forces and particles, but they just do not interact with (are invisible to) us?
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3answers
145 views

Universe to energy

Would it violate any known laws of physics to construct a universe containing no mass, only energy?
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2answers
813 views

What's the avarage temperature of the Universe?

I'm sorry if this was asked before but with all the stars and dark matter and all the other stuff, curently in the Universe, what's the avarage temperature of the Universe? Is it like extremely high ...
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2answers
4k views

Do we live in a world with 4 or more dimension?

A NOVA show have told the audience that we are live in 3 dimensional world, the world we lived in is compose by 3 element: the energy, matter, space. By the time Einstein have invented the ...
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0answers
232 views

Total positive charge in the Universe

In their last homework, some of my students miscalculated a charge to be $10^{20}$ C over a squared meter and I was wondering if there was as much positive charges in the entire Universe. It would do ...
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3answers
257 views

How do we know for certain that space is expanding?

How do we know for certain that space is expanding? Let's say that in the year 1950, we observe that galaxy 1 is 5 billion light years away from us and galaxy 2 is 10 billion light years away from ...
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1answer
187 views

What determines the end of space (universe)?

What determines the end of our universe? Is it defined by the farthest out physical object or is it defined by the farthest out form of energy like light?
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3answers
681 views

Looking out into the universe means looking back in time - how does that work?

This is a question that has been gnawing on me for many years now. Back a long time ago, as I recall in reference to a scene in a popular science show on TV, I was asked the following. The claim is ...
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3answers
150 views

Seeing cosmic activity now, really means it happens millions/billions of years ago?

A Recent report about a cosmic burst 3.8 billion light years away. It is written as though it is happening now. However, my question is, if the event is 3.8 billion light years away, doesn't that mean ...
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1answer
2k views

Can we see ALL of the observable universe?

Reading this wiki page about the observable universe, (and visible universe), implies that we humans, on this rock in the milkyway are seeing a static representation of the universe that is still ...
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1answer
110 views

Is there a relation between supersymmetry and entropy?

Considering that entropy denotes the level of order/disorder in a system, would it be possible for entropy and supersymmetry to exist at the same time? Or, are they entirely unrelated?
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1answer
1k views

Size of the Observable Universe [duplicate]

I wanted to know what the observable universe is so I was thinking and I thought, it must be age of the universe times 2. Well I was wrong. I found on one website that it is 46B LY across in each ...
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1answer
132 views

Speed of Universe Expansion [duplicate]

How much is the universe expanding every second (Earth second)? If you could be a bit simple in the answer that would be good.
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1answer
76 views

Why there is so much “nothingness” in the Cosmos?

I mean look how big is the Cosmos and hof few planets and suns are outthere, compared to the vast "nothingness" between them. With "nothingness" I mean no standard particles like atoms, electrons ...
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1answer
102 views

What is the age of universe? [closed]

As we know at the time of big bang as mentioned by the scientist the universe expanded faster than the speed of light. So does it mean that at that time all the particles present travelled in the time ...
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1answer
132 views

Finite amount of matter and space

(Please bear with me.) If the universe included multi-universes, and black holes transferred matter between them, AND yet there was a large, but FINITE amount of matter and space, How would that ...
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1answer
119 views

Antimatter in the universe [duplicate]

Is it possible that some parts of the universe contain antimatter whose atoms have nuclei made of antiprotons and antineutrons, sorrounded by antiprotons? If yes what can be the ways to detect this ...
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3answers
404 views

Could a universe with purely Newtonian mechanics exist?

I've heard about the fine-tuning principle and how if the fundamental constants of the Universe were changed even a slight bit, life could not exist as we know it. However, study on this subject ...
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1answer
223 views

In the big crunch theory, when the big crunch singularity forms, can the resulting black hole decay through hawking's radiation?

I've been pondering about this and I couldn't really find the answer for this. The big crunch theory postulates that the universe will eventually stop expanding and reverse back in on its self into a ...
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4answers
355 views

How was the universe created?

I do not know much beyond high school Physics. Thus, I am asking this question from almost layman's perspective: What, as per the best of our existing knowledge and widely accepted among the ...