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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How long was the universe radiation dominated?

Using the Friedmann metric I've been trying to calculate how long the universe was radiation energy dominated. I've reduced the metric to: $c.dt$ = $a(t).dr$ where a is the scale factor. I can work ...
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76 views

Experiments to resolve dillema between continuity and discrete

Which experiments/experimental methods are suggested to resolve an alternative about the structure of our universe space and time - is it continuous or is it discrete in a very small scale, especially ...
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116 views

Why did the big bang happen when it did?

Was there time before the big bang? I assume there wasn't, so is it even logical to ask if there was anything before the big bang? If there was time before the beginning of the universe, what happened ...
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3answers
109 views

Why is the universe expanding while its components actually attract each other?

First of all, what's the difference between gravity & gravitation? Anyway that's not the actual question. If every matter attracts each other toward itself, then wasn't the universe supposed to be ...
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96 views

Is Salah A. Mabkhout's hyperbolic universe theory convincing? [closed]

Did Salah A. Mabkhout develop a formula accounting for the flat rotation curve without a need for dark matter? Is his theory of the hyperbolic universe paradigm convenient? Did his theory connect both ...
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0answers
67 views

Is there a model of the universe with the transfinite (space)time?

In mathematics there is a concept of ordinal numbers where one can count to infinity and beyond. For example the least number that is greater than all the finite numbers is denoted by $\omega$. Such ...
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2answers
322 views

How accurately could we theoretically see into far space?

Travels to different galaxies are strongly limited by the speed of light. Unless we find a way to travel through space with some wormholes, we will never reach planets in another galaxy. But what ...
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41 views

Is a terminal gravitational center to the universe possible?

The current consensus is that there is no evidence of, or no way to tell whether or not there is a center to the universe. Considering our observable universe is only a small portion of what we know ...
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1answer
192 views

Is the Universe infinite or it's just expanding to infinity?

According to the WMAP data in the past years we can say that our universe is considered flat or at least nearly flat and we also know that flat universe is allowed to be both infinite or finite in ...
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282 views

What would happen if all dark matter disappeared?

This is related to this question which provided evidence about dark matter, and this question which asked what would happen if dark energy started disappearing. This question assumes that dark matter ...
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1answer
67 views

Do sound waves travel before Big Bang?

So I was reading a Scientific American article about how the universe is spreading apart and how it is getting faster. But in the article there was something that baffled be and it was this "Sound ...
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1answer
61 views

Why is the expansion of universe continuously increasing? [closed]

If our universe is expanding and the concept of the multiverse is true, then why is the rate of the expansion of the universe increasing? Surely it must decrease?
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54 views

Outer Space & Universe Expansion: [duplicate]

Experts agree that the stuff within the universe is moving farther apart from all the other stuff in the universe--much like the dots marked on the outside of a balloon that is being inflated. We ...
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2answers
89 views

If the Universe is going to last infinitely long, what is the type of this infinity?

Let's say we've built a machine, that prints a sequence of all natural numbers from 0 to $\infty$. We "could" do this in a Universe with an infinite amount time (if we also make many other assumptions ...
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1answer
56 views

How can a finite amount of matter be uniformly distributed in a flat, infinite space?

There are some properties of the Universe I find in the (mostly popular) literature which are often described as "the most probable in case of our Universe". I can't put them together in a way that ...
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2answers
95 views

How many dimensions our universe consists of?

Omnibus science convinces us in that we live within three-dimensional space. The coordinate measuring units XYZ. Quite controversial, but there are some legitimate theories clarifying why we live in ...
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1answer
85 views

Could this be a valid reason for why the universe could be infinite?

So, special relativity says that every frame is as good as any other frame, and there is no absolute frame of reference. All good. Suppose there is a finite universe (let's just assume the universe ...
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2answers
132 views

How fast does space/time travel?

It is said that before the big bang there was no before, as space/time was created in the big bang. The big bang creates a rapid expansion of space/time... so how fast is rapid?
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1answer
110 views

What is the value of the Universe's acceleration? [closed]

Please read this http://www.researchgate.net/publication/282157370_VALUE_OF_THE_UNIVERSE%27S_ACCELERATION Your ideas are welcome.
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1answer
233 views

How fast are we moving when standing still? [duplicate]

The Earth rotates around itself and revolves around the Sun. Our solar system revolves around the center of our galaxy and our galaxy is moving in some way throughout the universe. If you took into ...
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3answers
159 views

Where are the worlds in many-worlds interpretation?

What does it mean in MWI for other universes to exist? Are they in some sector of spacetime beyond our cosmic horizon or is it more complicated? I'm not asking this on Philosophy SE because people ...
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1answer
243 views

Is there a place in the universe where time doesn't exist?

I've been reading that, all laws of nature and the universe stop existing at a singularity. So where there is a singularity, there cannot be time. A singularity is created when a property of a system ...
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1answer
80 views

If everything in the universe doubled in size overnight, would objects in space appear to move slower? [closed]

I've been struggling with this question for a while. Imagine an object moving from planet A to planet B at a constant speed of lets say 10 m/s. If everything suddenly doubled in size, I would imagine ...
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2answers
81 views

could anti-matter black hole is sitting at the center of the universe ? that have all the aniti matter [closed]

i am very curious about the space , matter and anti-matter , i am not a scientist but i have few question , can we calculate the speed of expansion of the universe? , i have made some assumption or ...
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1answer
54 views

Singularity - Origin Point

How can it be said that the real beginning of the real universe involved a "singularity of zero size and infinite density of mass" when no space existed at all to define any density and when nothing/...
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2answers
70 views

How would Boltzmann Brain function with all anti-matter in it? [closed]

Please cope with me, I have been thinking about Boltzmann Brain yesterday and if Quantum fluctuations always happen in pairs of particle and antiparticle since sum of all energy has to be 0. My brain ...
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4answers
350 views

Boltzmann brain vs Actual universe probability actual calculations [closed]

I have been reading lots of physics lately about how universe came into being. One idea is that universe is long gone (thermal death) and it might not exist the way I feel it and I am a sequence of ...
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3answers
234 views

How does dark energy allow the universes expansion to accelerate?

I was wondering how dark energy is effecting the rate at which the universes expansion occurs.
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4answers
360 views

Virtual Particles real? Virtual particles create a universe?

I am reading the book of Lawrence Krauss "A universe out of nothing", where he explained that the vacuum is not empty. It is a boiling brew of virtual particles that come out of their existence. And ...
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0answers
39 views

Do the entropy of the universe and third law of thermodynamics conflict? [duplicate]

We know that our universe was in low entropy state at the earlier time after the Big bang. But we also know that the temperature at that times was enormously high. But what the third law of ...
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49 views

Equilibrium temperature of the universe [duplicate]

At what temperature will the universe eventually equilibrate?
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1answer
139 views

Pre Big Bang knowledge

I have read that no one knows what preceded the Big Bang, but is this true? The Big Bang process (with or without inflation) followed known rules which “existed” prior to time zero. For example, some ...
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2answers
425 views

What is the physics in a spacetime with only two point masses?

Imagine a universe consisting of only two point masses, neither of which are in motion. Would they be drawn towards each other? Does there need to be motion for the curvature of spacetime to affect ...
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0answers
23 views

The universe is said to have begun as a singularity, but how do we know nothing else existed? [duplicate]

When I imagine the big bang, I first imagine a tiny ball surrounded by black void. Then the ball explodes and the universe begins. I assume most physicists have the same basic idea. But how do we ...
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2answers
165 views

Is the universe a Turing machine?

Reading about Computable numbers I wondered if there is any physical experiment that returns non-computable numbers or if there is any physical theory that needs non-computable numbers. Because if ...
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1answer
77 views

Could the Big Bang have simply been two black holes hitting each other at 99% of the speed of light? [closed]

Given two equally massive black holes moving at 99% of light speed, it seems there would clearly be enough energy for most (99%?) of the mass of both to be ejected and / or radiated well beyond the ...
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2answers
101 views

Gravitational waves in general relativity

After reading some concepts of general relativity,is it true that the universe communicate with its different constituents (stars, galaxies, etc...) via gravitational wave? If so, how is that? Do ...
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1answer
73 views

What is Drake equation?

I was reading an article on aliens, where I found something called Drake equation. I tried to understand it, but just couldn't get it in my head, as I belong to class 11. So, can anyone explain me it ...
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0answers
27 views

Does the Big Bang Theory explain about the formation and destruction of matter? [duplicate]

I read here here that, The Big Bang theory explains how the universe was created. Even though it was unable to explain that how everything in the universe did came to existence from no matter state ...
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3answers
131 views

Is there any situation in which a primordial black hole-sized black hole form AFTER the “Big Bang?”

I have seen that primordial black holes may have formed at the start of the universe due to the density of matter. So, is there any way in which our current Universe could spawn a non-stellar mass ...
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1answer
49 views

Equations for Big Bang expansion, distance and energy

On the back page of the CPEP poster “The History and Fate of the Universe” a table gives distance scale (size), temperature, and energy (radiation) for seven expansion times (10-43 sec to now). http://...
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1answer
77 views

Fractional number of particles in the universe?

Is it possible, that the metagalaxy contains a fractional (non whole) number of particles or fractional number of a particular kind of particles (such as electrons)? Sorry, if my question is stupid, ...
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1answer
84 views

Traveling Back in Time at the End of the Universe [closed]

I apologize if this question may seem fantastical. Since the heat death of universe is said to be inevitable, is it possible to travel back in time to a younger universe when the time comes? Is that ...
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2answers
243 views

Could we be on the inside of a concave hollow universe?

Recently I was discussing this theory again (a little drunk, I admit) and then tried to find answers, but couldn't find anything satisfying. There is a theory (or several theories) that we could be ...
2
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1answer
126 views

How can the Hubble telescope see the light from galaxies that are millions of light years distant?

The Hubble Space Telescope is in the news every now and then. How can it photograph galaxies that are millions of light years from Earth? We can understand that light comes from galaxy and Hubble "...
5
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1answer
103 views

Since space expands (and can theoretically contract) faster than light, does that mean that in a big crunch information could travel FTL?

Layperson here. In a theoretical big crunch with space contracting faster than the speed of light, would information be travelling faster than speed of light? Because the points A and B themselves ...
5
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2answers
73 views

Is there a proof that space expanding produces observers at all points that see what we see?

I know that galaxies are moving away from us, and so can see that it's intuitive that if space was expanding, then the astronomical observations from Earth would be the same as at all other points in ...
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83 views

About Fermilab's holographic experiment

I read this article. I am no professional, and certain statements left me wondering. They say: “We are specifically trying to determine if there is a limit to the precision with which we can ...
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1answer
54 views

Evolution of dark matter and gas temperature

So I have recently watched a simulation of dark matter density and gas temperature evolution in a universe. However I couldn't find description of under what assumptions it was was made and what it is ...
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Am I attracting Pluto?

My question is simple: as the title says, am I exerting a force over for example Pluto, although it is a very small force, it is there, right? Or maybe let's go further: Am I exerting a gravity force ...