Time Dilation and Absolute Age of the Universe

[origin]

Hi, this has been an interesting read for me.

One of the puzzles I have been contemplating lately regarding time and when it began relates to the moment when the initial inflationary period of the universe abated. Since the universe was expanding in all directions at once at greater than light velocity (at least very briefly) it seems to me that time could not decompress enough to be observable until that period of inflation had subsided. If, during inflation the universe did expand faster than light (see Guth, inflation theory) then one might assume that time was literally going backwards, in which case the universe would not have materialized or expanded at all. Since this is not the case and we are here and going "forward" through time, I can only surmise that time itself is dependant upon at least one of the 4 principal forces that seperated to form the laws of physics that we know and enjoy today. FWIW, I think it is a shame that we don't seem to have a better understanding of what time actually is than we did to begin with..

You are trying to apply the theory of special relativity to the universe instead of things in the universe. There is no prohibition against the universe as a whole expanding faster than the speed of light and in that case there is no affect on time.

 

[Jerromy]

Exactly, Origin... there is no effect on time for everything expanding away from the clock. If inflation is true then clocks, much like the twins in the paradox, would keep the same time while space expanded between them. The essence of time therefore lies in the fight against expansion to keep the clock together. If the expansion is accelerating then time is running out faster.

 

[ramparts]

Thread necromancy makes me sad.

 

[babea]

You can find similarities in just about everything, I once read a physicist likening the solar system to the atomic structure whereas the electrons would be represented by the planets in orbit.

Regards.

 

[MeteorWayne]

Which is an idea from 50 years ago, and we now realize is totally incorrect.

Welcome to Space.com

 

[babea]

Thanks Meteor...just stating an example.

 

[csmyth3025]

This thread raises a question I believe I posed in another thread - unfortunately I can't remember the details.

Basically, I wondered if the passage of time (as we know it) may have been much slower when the Universe was very young (perhaps less than a second as we measure time) and there was an intense gravitational field due to all the compressed matter and energy.

Nowadays we've determined that various stages in the development of the early universe took place at certain (extremely small) fractions of the first second (as we measure a second). Could it be that these events occurred over vast stretches of time (as we now measure time) because time itself was crawling along at a near stand-still in the intense gravitational field?

This speculation doesn't change anything about the sequence of events proposed to have taken place in the first few moments of the Universe - but it certainly makes me think about time dilation.

Chris

 

[SpeedFreek]

Time always runs at the same speed - 1 second per second. This was as true in the early universe as it is today. So, theoretically, if you were present during the first second of the universe, it would have all happened within a second.

Now consider a type 1a supernova at redshift z=1. The "flash" of the supernova lasts around 20 days, from our point of view. But when we see a similar event at z=2, it lasts around 40 days. We assume the events were similar - i.e. local to those events, they lasted approximately the same length of time. But due to the expansion of the universe, we see those events as lasting different apparent times, which is known as cosmological time-dilation.

If it were possible for us today to see the events during the first second of the Big-Bang, they would apparently last a very long time, so one might conclude that time was running slower back then. But if you were present back then you would experience them all within a second, so time was not running slower back then. What is happening here is that we are coming across the difficultly in meaningfully transforming the laws of physics in our current frame of reference with a frame of reference from long ago, when there is no way for us to meaningfully compare them - we cannot go back to that "place" to check - if we could, we would find it all happened in a second!

But from that frame of reference living back in the first second, if they stayed in that frame all the way through time until today, they would say the universe was 13.7 billion years old, and that a second always lasted the same length of time. When they got here, they would find that seconds today last as long as they ever did.

Just as with the paradox of the twins, the only time the comparisons become "absolute" are when you bring the relevant frames of reference back together, and we cannot do this for the history of the universe.

 

[csmyth3025]

Time always runs at the same speed - 1 second per second. This was as true in the early universe as it is today. So, theoretically, if you were present during the first second of the universe, it would have all happened within a second...........
...........If it were possible for us today to see the events during the first second of the Big-Bang, they would apparently last a very long time, so one might conclude that time was running slower back then.....
.......Just as with the paradox of the twins, the only time the comparisons become "absolute" are when you bring the relevant frames of reference back together, and we cannot do this for the history of the universe.

I think I see what you mean. I originally started thinking about this when I read that unstable particles accelerated to relativistic speeds appear to us to have half-lives which are longer than the same particles that are "at rest" relative to us. As you point out, this apparent difference is the result of timing the breakdown of the particles with a clock embedded in our frame of reference. To the particle, its half life is always the same - whether it's moving (relative to us) or "at rest".

Chris

 

[csmyth3025]

Time always runs at the same speed - 1 second per second. This was as true in the early universe as it is today. So, theoretically, if you were present during the first second of the universe, it would have all happened within a second.

Now consider a type 1a supernova at redshift z=1. The "flash" of the supernova lasts around 20 days, from our point of view. But when we see a similar event at z=2, it lasts around 40 days. We assume the events were similar - i.e. local to those events, they lasted approximately the same length of time. But due to the expansion of the universe, we see those events as lasting different apparent times, which is known as cosmological time-dilation.

If it were possible for us today to see the events during the first second of the Big-Bang, they would apparently last a very long time, so one might conclude that time was running slower back then...

Following up on this thought, I'm thinking about the accelerating rate of expansion of the Universe we observe today compared to the rate of expansion that occurred during the inflationary period at the beginning. Does General Relativity provide us with a means by which to compare these two rates of expansion?

Here, again, I'm envisioning a situation in the early universe where, by virtue of the intense energy/mass density, a kilometer might be 10 meters as we measure it today and a second might be 100 seconds as we measure it today. It's entirely possible that I have this concept completely wrong. I'm open to suggestions.

Chris

 

[Floridian]

Even if you were to measure the vibrations of every electron, wouldn't that just be the average time of the universe (would this be the "actual time" for all intensive purposes?)

What you would need to do is perhaps combine the effects of time dilation and the effect of gravity so that they balanced out and equaled a quantifiable figure if that makes sense. I don't think it does though.

You also have to define "old". Unless there is a time outside of the universe, you'd just be measuring the average age of the universe which I guess would be its actual age.