Age of Universe - Is time the same today as at the beginning

[anonymous]

My question has to do with determining the age of the universe and the measurement of time. Is it possible that at the beginnings of the universe, time past more quickly than it does today. If time is not constant, is it not possible that at the beginning of the universe a billion years would seem like 100 to us today? Time moved more quickly.

[Tormod]

Well, what do you base this idea on? What makes you think time is not constant? Please explain.

Tormod

[deamonstar]

hmm... according to Einsteins special realativity time slows in areas of extreme space curvature, such as the immediate area outside of a black hole's event horizon. if this thought is applied to the moments just after the big bang, then one could assume that with all of space confined to such a small area that gravity would be immense to say the least (I am disregarding the effects of expansion at this point for arguments sake), therefore causing time to move more slowly... not faster. this would allow the events of the big-bang to happen at a realativly faster rate than at present times without violating the light-speed limit.

[Daisy]

I was under the impression that time was not constant, based on theory of relativity. Therefore I thought it possible that time could move at different rates depending on the stage of the universe (whether at the beginning or now).

[Tormod]

To my knowledge relativity states that time is relative - for an observer's time-frame. This applies to everything that is in motion, thus the term "relativity" (_very_ oversimplified, for the sake of argument).

To pose the question of whether time can move faster or slower, one needs to ask "for what does time move faster or slower". I wonder if perhaps it is too easy to just state that "time moved more quickly in the past". The follow-up question needs to be, "according to what?".

If time is relative for each object according to its relative speed, then it makes no sense to talk about a speed of time for the Universe as a whole. The only way we can measure the speed of time for the entire Universe, would be to measure it against something other than it - like another Universe.

Basic relativity example: When someone flies away in a spacecraft close to the speed of light while another person stays behind on Earth, they will each see each other's clock slow down. But they will both perceive _their own time_ as moving _at a normal rate_. (I think it is impossible to define the word "normal" in that phrase.)

The person travelling near the speed of light will survive the person staying on Earth by thousands of years. Yet the star traveller does not actually live any longer (he will live, say, only one normal lifetime in his own time-frame), even though we perceive him to be inside the Universe for much longer! (speculation, of course - this has never been tested).

I think the consequence of this logic is that for everything, time moves at a steady rate, but no two things ever move at the exact same rate. For the Universe as a whole, there is no such thing as a "speed of time".

Time is simply a dimension, separating the present from the past and allowing things to change into the future. Whether it was faster or slower in the past makes no sense. The Universe will still be as old as we perceive it to be, because we measure it by observing the light.

If we learn that light has travelled faster or slower in the "early days", we can adjust our age estimate. But we cannot ever be sure, because we must see everything from our own point of reference.

Tormod

[deamonstar]

hey tormod... check out this link. I think that you may find it interesting.

http://hyperphysics.phy-astr.gsu.edu...iv/airtim.html

oh... and this one too...

http://hyperphysics.phy-astr.gsu.edu...v/tdil.html#c2

[Tormod]

Thanks. That's a good site.

I may be wrong, but what I don't see is this: where is anyone stating that it is _time_ that changes, and not the perceived passing of time? I only seem to find experiments which show that clocks slow down and show incorrect time. I don't find any evidence that time slows or speeds up.

Considering that the original question in this post was the age of the Universe, my point is that things move through time at different speeds, but the actual flow of time cannot be defined as having an absolute speed. For the Universe as a whole, it makes no sense to say time was faster or slower in the past, because you would have to add up and subtract all the various speeds through which the individual objects are moving.

Here's an analogy: you can easily measure the speed of a boat on a river. But how do you measure the speed of the river?

Tormod

[deamonstar]

I understand your point completly. I too have used the "perceived passing of time" argument with others. it is the speculation on this subject that I enjoy. this is how postulates come about, leading to theories and experiments... and new ideas and laws!
how do I measure the speed of the river? ahh... a trick question. your analogy would force me to infer that I could not compare the speed of the river with anything but the river itself (or possibly the boat), hence, I could not compare the rate of time with time.
it is indeed a difficult thing to measure, the age of the universe, when the definition of time is so poorly understood. we must continue exploring this however. one day someone will ask the right question....

[anonymous]

What if for argument's sake we determine that light at the beginnings of the Universe traveled at twice the speed it does today. How would that alter the age of the Universe? I am assuming that the faster light travels the younger the Universe would be?

[Tormod]

Yes, _if_ we can safely assume that our method of measuring the age of the Universe by measuring (the distance we can see divided by the known speed of light) is correct, then the known Universe would indeed (logically) be much younger if the speed of light was much faster in the past.

That said, most of the astronomical evidence up until very recently did not consider this. Lately, however, some researchers (Paul Davies, John Barrow and others) have pointed out that the constants of nature may not be so constant at all, and that the speed of light may actually have slowed down. But we're not talking extreme values here, merely 1 part in a trillion or so...(don't have the figures in my head) - but we have recently discussed this elsewhere in the forums.

Tormod