Tagged Questions
3
votes
1answer
71 views
Diameter of the universe [duplicate]
Should the diameter of our universe always be more than its age in light years?
As if the distance between any two points in the universe is equal to 13.5 billion light years then the light from the ...
2
votes
0answers
43 views
Cosmic Inflation: Lower Expansion Rate with than without?
When I read the Cosmic Inflation diagram at
https://en.wikipedia.org/wiki/File:Horizonte_inflacionario.svg
which I rotated to make it readable:
where the Hubbleradius, and therefore also the ...
1
vote
2answers
91 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 ...
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?
0
votes
3answers
81 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
113 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 ...
1
vote
0answers
37 views
When spacetime expands to the point where galaxy clusters are not observable, will there by any interaction?
It's my understanding that in a few billion years, clusters of galaxies won't be able to directly observe one another due to the expansion of spacetime overcoming gravity between those clusters. ...
4
votes
1answer
96 views
Why don't orbits expand with the Universe?
Consider two bodies orbiting each other.
As the Universe expands would the distance between them increase?
Most people say that a gravitationally bound system will not expand with the Universe. They ...
2
votes
2answers
39 views
About hubble observatory and distant galaxies [duplicate]
According to Hubble observatory, the age of universe is 14 billion years. But, the distant galaxies are about 40 billion light years. How could that simply be possible? That means the information that ...
4
votes
2answers
296 views
Why cosmic background radiation is not ether?
why cosmic background radiation is not ether? I mean it's everywhere and it' a radiation then we can measure Doppler effect by moving with a velocity.
1
vote
3answers
155 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 ...
3
votes
1answer
203 views
Galaxies moving away at the speed of light
As an arts student, I really find those cosmological questions hard to understand and hence come here to seek your kind help.
The Hubble constant $H_0$ is estimated to be about 65 km/s/Mpc, where 1 ...
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 ...
3
votes
2answers
145 views
Universe Expansion and two tennis balls
Clear the universe of all matter except for two tennis balls. Place the two tennis balls in the same inertial frame 1 Mpc apart.
Are the tennis balls getting further apart?
Will the tennis balls ...
0
votes
1answer
173 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.
7
votes
1answer
126 views
Gravitationally bound systems in an expanding universe
This isn't yet a complete question; rather, I'm looking for a qual-level question and answer describing a gravitationally bound system in an expanding universe. Since it's qual level, this needs a ...
2
votes
2answers
134 views
Why the temperature is getting lower when the universe is expanding
As we know, if an ideal gas expands in vacuum, as its energy is unchanged, the temperature remains the same. An ideal gas's energy does not depend on volume. In general, the energy is $kT$ times the ...
1
vote
0answers
44 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
109 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 ...
1
vote
1answer
77 views
Redshift and shapes of galaxies
How does peculiar velocities lead to the observed elongation of galaxy clusters in redshift space, otherwise known as the Fingers of God effect? I have read the relevant Wikipedia page, but cannot ...
0
votes
1answer
70 views
Time for Light to travel from most distant objects in universe
I understand that it is possible to detect the most distant objects in space over 13 billion light years away from us and that the universe is 13.75 billion years old.
Does this imply that there were ...
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 ...
0
votes
1answer
69 views
How to understand movement in expanding universe?
I know that universe is expanding equally between every pair of points but it was a single point in it's very past... so I was wondering if we could locate this center point of universe. Now I know ...
4
votes
6answers
189 views
Why are distant galaxies not actually tiny bits of matter?
Distant galaxies are said to be moving away from the Milky Way (and us) at speeds approaching the speed of light. Since Special Relativity tells us that any object moving away from us at a velocity of ...
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 ...
1
vote
2answers
217 views
Cosmology questions from a novice
These ideas/questions probably represent a lack of understanding on my part,
but here they are:
1) Cosmologists talk about the increasing speed of expansion of the universe and talk of dark energy as ...
0
votes
1answer
301 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.
...
-5
votes
3answers
186 views
Could some Red and Blue shifts be the result of light passing through “dark matter”?
As i see it, light behaves in certain ways, as the Double Slit experiement shows,
So when light comes into contact with dark matter, it becomes both a wave and a particle, the wave is bent around the ...
2
votes
0answers
84 views
Can decompactification explain the inflation of the early universe?
I've just reread chapter 11 of this book where it is explained among other things, that our four dimensional universe could be unstable concerning a decompactification transition, since potential ...
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 ...
0
votes
3answers
120 views
Accelerating expansion of the universe and cyclic model
So I've heard that recent observations indicated that the rate of expansion of the universe is accelerating. Does this indicate that the universe can NOT be cyclical, with an infinite series of big ...
1
vote
1answer
171 views
Do atoms expand with universe? [duplicate]
Possible Duplicate:
Why space expansion affects matter?
Why does space expansion not expand matter?
As we know, the universe is expanding, galaxies are away from each other. But what ...
2
votes
1answer
177 views
Light coming from distant galaxies
Some of the distant galaxies appear to be receding from us faster than the speed of light due to stretch of the space between us and those galaxies.
By an analogy with the ant on a rope paradox, the ...
2
votes
4answers
188 views
Space Expansion vs. Relative Motion
Inspired by a recent dialogue from another question:
Given 2 objects moving at some velocity $v$ relative to one another, is it possible to determine whether they are moving or whether the space ...
1
vote
1answer
328 views
Does the large red shift value of galaxies mean they are far away?
When the red shifts of galaxies are large, why do we think that they are far away?
I know about Hubble's law, Tully-Fisher relation of spiral galaxies, Faber-Jackson relation of elliptical ...
3
votes
4answers
337 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
6answers
588 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 ...
0
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0answers
22 views
Expansion of Universe [duplicate]
Possible Duplicate:
Why space expansion affects matter?
If the Expansion is prevalent, i.e. it is observable and true then shouldn't that result in the expansion of the Milky Way galaxy, ...
0
votes
0answers
14 views
Expansion of Universe. Will it come to an end? [duplicate]
Possible Duplicate:
Is there a consensus on the fate of our universe?
Its been about 13.7 billion years past the Big Bang took place. According to Hubble's law, the universe is under ...
1
vote
1answer
210 views
spacetime expansion and universe expansion?
First of all, does the expansion of spacetime solely cause the expansion of universe?
Secondly, if spacetime is the sole cause, do objects(matter with mass) themselves expand?
Thirdly, by spacetime ...
0
votes
1answer
192 views
Is the FRW metric describing the shape of the universe or the shape of the expansion applied to the universe?
Is it (the output, i.e, spherical, flat, hyperbolic) describing the physical shape of the universe and its curvature at any given instance of time or is it describing the shape of the expansion ...
2
votes
2answers
120 views
How to test whether galaxies are moving away from each other in a static background or whether space is being created beween them?
Observations show that galaxies are moving away from one another on the macroscopic scale.
Now, scientists interpret this by saying this happens not because galaxies are really moving away from each ...
1
vote
1answer
230 views
Superluminal expansion of the early universe how is this possible?
Is this a postulate? I get the expansion of the universe, the addition of discrete bits of space time between me and a distant galaxy, until very distant parts of the universe are moving relative to ...
1
vote
1answer
336 views
How is the expansion of space itself explained in LQG?
To explain the expansion of space I have often heard people saying that space is continuously created. This picture is usually applied to cosmological scales but I`m nevertheless curious if some ...
2
votes
1answer
249 views
how many times have the first photons lapped the universe?
I'm not really interested in the actual number of times, but rather an explanation of a closed Universe. How do we still measure the background radiation of the Big Bang? Those electromagnetic waves ...
2
votes
1answer
130 views
The range of light
It occurs to me that the empirical evidence shows that there is a point out in space where light stops coming from.
Putting aside the expansion of the universe for a second, and focusing strictly on ...
3
votes
2answers
501 views
Value of the Hubble constant over time
There is something I don't understand about the Hubble "constant" H, as it seems to clump two concepts together that I can't quite unify in my head. On the one side, we have
V = D * H
which means ...
6
votes
3answers
96 views
Universe is expanding at enormous speed
I'm not an expert but I've come to understand that the universe is expanding at enormous speed. That means that all of the visible galaxies are moving away from us at great speed.
I also came to ...
