The universe tag has no wiki summary.
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1answer
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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 ...
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2answers
269 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 ...
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2answers
399 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 ...
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6answers
1k views
What is known about the topological structure of spacetime?
General relativity says that spacetime is a Lorentzian 4-manifold $M$ whose metric satisfies Einstein's field equations. I have two questions:
What topological restrictions do Einstein's equations ...
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4answers
536 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 ...
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1answer
99 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 ...
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2answers
231 views
Are we big or small?
How does the size of humans compare to the size of other objects in the universe? Are we among the relatively large or the relatively small things?
My very preliminary research suggests that the ...
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1answer
227 views
Is the structural similarity between atoms ( smallest) and universe (biggest) a conincidence. Or there can a reason for this beyond imaginations
Is the structural similarity between atoms ( smallest) and universe (biggest) a coincidence. Or there can a reason for this beyond imaginations.
It seems like, if one starts travelling from atoms... ...
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0answers
50 views
Why does $H_2$ form on such a long time scale?
If we were trying to figure out the time scale for a gas-phase reaction between two hydrogen atoms in a molecular cloud (which has density $~10^4/$cm$^3$), apparently the reaction would happen on a ...
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5answers
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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 ...
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2answers
206 views
Did the universe always have 4 space time dimensions?
Is the dimensionality of spacetime in all usual models constant?
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1answer
89 views
Nature of an explanation [closed]
An explanation always refer to something earlier in time. Since A and B existed, then C had to happen because of universal laws of physics.
If "The Universe" is everything that exists and has ...
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2answers
498 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 ...
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2answers
1k views
Is reality discrete at the quantum level? (…and what does it imply not only mathematically?)
On a quantum scale the smallest unit is the Planck scale, which is a discrete measure.
There several question that come to mind:
Does that mean that particles can only live in a discrete grid-like ...
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2answers
192 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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4answers
105 views
Could there be more universes?
In the documentary: "Curiosity - Did God Create the Universe (on YouTube)", theoretical physicist and cosmologist Stephen Hawking states that time did not exist before the big bang.
The first ...
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2answers
258 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 ...
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0answers
50 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 ...
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3answers
215 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 ...
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1answer
94 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 ...
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1answer
63 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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7answers
2k views
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 ...
5
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2answers
811 views
A Fermi-question: Are there more stars than grains of sand?
This claim is pretty popular in the web and obviously cannot be answered by counting grains or stars. Thats what physicists call a Fermi-question. It deals with problems/questions where we dont have ...
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2answers
80 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 ...
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1answer
473 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 ...
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8answers
2k views
Is time continuous?
I was making universe simulations, and I noticed that I implemented discrete time (the only type possible on computers). By that, I mean that I had an update function, that was called many times per ...
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1answer
129 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 ...
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2answers
441 views
how can galaxies collide if everything moving outwards
If the universe started from Big Bang and everything is expanding outwards and actually accelerating away from each other, than "How is it possible for two galaxies to collide as they all are moving ...
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3answers
685 views
Is there a finite amount of mass in the universe?
So, I'm not too physics savvy but I am curious to ask. Is there a finite amount of mass in the universe? or is there more and more being created from somewhere or something? If the universe is ...
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2answers
235 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 ...
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2answers
389 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?
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4answers
363 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 ...
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1answer
75 views
Cosmological constant of standard model of cosmology and observational data
I am curious whether the current Lambda-CDM model of cosmology matches well with observational data, especially expansion of the universe.
How well does Lambda-CDM defend its established status from ...
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1answer
174 views
If the universe is infinite, shouldn't I already have been contacted by a time and space travelling doppelgänger?
If the universe is infinite, by virtue of chance it means that every possible configuration of matter must exist somewhere (according to this documentary).
Therefore, if we accept that the universe ...
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1answer
310 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 ...
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4answers
960 views
Is spacetime discrete or continuous?
Is the spacetime continuous or discrete?
Or better, is the 4-dimensional spacetime of general-relativity discrete or continuous? What if we consider additional dimensions like string theory ...
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2answers
1k views
Size of universe after inflation?
Wikipedia states the period of inflation was from $10^{-36}$sec to around $10^{-33}$sec or $10^{-32}$sec after Big Bang, but it doesn't say what the size of the universe was when inflation ended. ...
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6answers
610 views
Does gravity slow the expansion of the universe?
Does gravity slow the expansion of the universe?
I read through the thread http://www.physicsforums.com/showthread.php?t=322633 and I have the same question. I know that the universe is not being ...
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1answer
117 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
893 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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3answers
581 views
How can we be so sure the universe has 3 dimensions?
I'm just a layman here so please bear with me if I don't get all the words or theories by correct name or whatever. I hope it will be clear enough what my question is. Here goes:
When I read articles ...
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1answer
344 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
715 views
Zero energy universe
Regarding this thread:
http://www.physicsforums.com/showthread.php?t=506985
Why is the idea that the total energy in the universe "zero" so popular (re: Laurence Krauss) and why is the flatness of ...
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1answer
127 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
158 views
How fast was the universe expanding during the inflationary period?
Compared to how fast it is expanding in the post-inflationary period (now)
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2answers
252 views
Does the current acceleration of universe imply that our universe is open?
Does the current acceleration of universe imply that our universe is open?
If the universe is closed, from the Friedmann's equation, the acceleration of universe wouldn't be possible, would it be? (Of ...
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1answer
126 views
A question about multiverse
I have a question that I would like to ask here since I'm not an expert or any near to that.
Actually I just came up with this question when I was watching The fabric of cosmos.
I couldn't find where ...
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1answer
177 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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4answers
381 views
Can the big bang be “light turning into space” at the edge of the universe?
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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1answer
67 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 ...
