Tagged Questions
2
votes
1answer
45 views
Questions about the Jeans length
I have a couple of questions about the Jeans length. Suppose the universe has a homogeneous energy density, except there's a spherical region that is overdense.
I understand that if the region is ...
1
vote
2answers
89 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 ...
0
votes
1answer
80 views
Is the underlying pattern of all dynamical physical processes in the universe actually chaotic? [closed]
After studying and pursuing research interests in chaos theory since the mid-1980s, I have to question whether standard physics (including all physical theories we currently use at all scales of size ...
1
vote
2answers
71 views
If everything in existence were increasing in size at some rate, would we be able to detect it?
Would our eyes observe any changes?
What about electronic measurement devices?
-2
votes
2answers
111 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 ...
0
votes
3answers
80 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?
0
votes
3answers
112 views
Cosmological redshift interpretation
Can the cosmological redshift be interpreted as atomic frequencies increasing by the scale factor as the Universe expands?
This explanation seems closer to the truth than the popular idea that a ...
0
votes
1answer
90 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?
2
votes
1answer
66 views
How fast did hydrogen atoms travel when they were first formed in the early universe?
I can't seem to find any data on this, is it a known value?
1
vote
3answers
145 views
Can space expand with unlimited speed?
At the beginning, right after the Big Bang, the universe was the size of a coin. One millionth of a second after the universe was the size of the Solar System (acording to ...
1
vote
3answers
125 views
Universe to energy
Would it violate any known laws of physics to construct a universe containing no mass, only energy?
3
votes
2answers
174 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 ...
2
votes
1answer
128 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?
3
votes
3answers
119 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 ...
0
votes
1answer
171 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 ...
0
votes
1answer
78 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.
1
vote
1answer
72 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 ...
1
vote
1answer
77 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 ...
1
vote
0answers
43 views
Is the speed of light the ultimate speed limit? [duplicate]
As we all know nothing can go faster than the speed of light as mentioned by most of our pioneer's in physics. But as I was listening to one of the statements of Sir. Stephen Hawkins he stated that at ...
2
votes
1answer
107 views
acceleration of the universe
Moments after the Big Bang, the universe was expanding at an incredible rate, (I've heard) faster than the speed of light. Due to dark energy, scientists predict the rate of expansion will pick up ...
7
votes
3answers
282 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 ...
-2
votes
1answer
109 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 ...
10
votes
5answers
481 views
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 ...
3
votes
0answers
37 views
In the Ī±Ī²Ī³ cosmology paper, how do the authors assume the integral of density over time in the early universe?
In the famous Alpher-Bethe-Gamow paper, the authors say: "it is necessary to assume the integral of $\sigma_n dt$ during the building-up period is equal to $5 \times 10^4 \frac{\text{g ...
4
votes
2answers
157 views
Total Energy of the Universe?
I've heard the total energy is zero, but I've also heard it cannot be said to be zero since there's so much unknown stuff in the universe. Is that true?
1
vote
1answer
162 views
Parallel universe and Infinite monkey theorem [closed]
Is the Infinite monkey theorem helpful for determining the existence of the very same our universe somewhere else?
3
votes
0answers
74 views
Conservation of Energy in the Universe [duplicate]
Possible Duplicate:
Is energy really conserved?
Why canāt 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 ...
3
votes
3answers
196 views
If everything in the universe doubled in size overnight, would it be noticeable?
By my understanding, if everything doubled in size, such as the Sun and the Earth, and because the space in between them (which is nothing) can't expand, would the gravities greatly change and the ...
2
votes
2answers
470 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 ...
5
votes
3answers
205 views
Is observable universe an explanation against Olbers' paradox?
First of all, let me tell you that I'm not a physicist but rather a computer scientist with a mere interest in physics at nowhere near a professional level so feel free to close this question if it ...
4
votes
3answers
220 views
Do new universes form on the other side of black holes?
I have four questions about black holes and universe formations.
Do new universes form on the other side of black holes?
Was our own universe formed by this process?
Was our big bang a black hole ...
2
votes
2answers
263 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 ...
2
votes
1answer
92 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 ...
0
votes
1answer
298 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.
...
2
votes
2answers
190 views
Did the universe always have 4 space time dimensions?
Is the dimensionality of spacetime in all usual models constant?
3
votes
2answers
180 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.
...
2
votes
4answers
283 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 ...
0
votes
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 ...
4
votes
3answers
192 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
votes
1answer
93 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 ...
6
votes
3answers
444 views
Is the total energy of the universe constant?
If total energy is conserved just transformed and never newly created, is there a sum of all energies that is constant? Why is it probably not that easy?
2
votes
1answer
62 views
Why is that the space-time associated with the Earth is not shrinking?
If we apply the Friedmann LemaƮtre 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 ...
8
votes
9answers
740 views
Can a universe emerge from nothing?
If the Universe is flat and the total energy of the universe can be zero (we don't know if it is, but many theorists support the idea, i.e. at BB initial conditions:
t = 0, V = 0, E = 0) then is it ...
0
votes
2answers
79 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 ...
2
votes
1answer
123 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
votes
2answers
350 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
votes
4answers
336 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 ...
0
votes
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 ...
3
votes
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. ...
3
votes
6answers
586 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 ...
