Time Dilation and Absolute Age of the Universe

[mabus]

A thought experiment occured to me that is, somewhat kooky. I'm hesitant to even post it here, except that I'm somewhat interested in the implications and thought others may perhaps find it interesting.

To set it up, it seems fairly common sense to imagine that the universe has a finite span of time. We imagine it beggining x number of years ago in the big bang, and (assuming the big crunch model is correct) ending at some finite time in the future. Of course it may go on expanding for an eternity, this is not the point, the point is that if it has a final end, it will end at a determinable amount of time in the future. It's life history can be accurately dated and timed. While we may age at different rates based on time dilation, surely the universe ages at a finite set pace. Right?

So the thought occured to me, what if we had a clock in the universe from the moment it emerged from the big bang to the moment it died in the big crunch. Would we not then, have a finite defined amount of time elapsing which we would recognize as the duration of the universe. It certainly seems reasonable to me anyway, but time dilation presents a bit of a problem to, what otherwise seems like a rather common sense conclusion. Let's set the experiment up so I can show you what I mean, and hopefully someone can show me where I'm in error.

So let's assume that at the moment of the big bang (which we are going to assume is the origin of the universe for the purpose of this experiment) an atomic clock emerged. Yes I know atoms had not formed yet, much less clocks, but we will dismiss that objection for the purpose of this experiment. This clock will measure the duration, or the elapsed time of the universe from the moment of the big bang, until the big crunch (which we are going to assume will be the end of the universe for the purpose of this experiment)

Now, atomic clocks measure time by detecting the vibrations of electrons inside atoms (feel free to correct me if I am mistaken), so such a clock, emerging with the big bang, and ending with the big crunch, would measure the exact finite number of vibrations of electrons in the universe throughout the entire existence of the universe.

Now, imagine we were to build a second newer atomic clock, several million years after the big bang.

We would now have two atomic clocks. One measuring the elapsed time from the moment of the big bang, and one that began to measure time several million years later.

We've already established that the electrons in the universe would (according to the original atomic clock) have a finite number of vibrations. Just for simplicities sake let's call this 1X.

The second clock measures the vibrations as 1X - 1MillionY
That is to say, whatever finite number of vibrations in the lifespan of the universe is, minus the amount in 1 million years.

Here's where time dilation causes a problem.

If we place the original clock on a rocket, and leave the second newer clock on earth, then the original clock will see time elapse more slowly than the clock back on earth. In other words, the clock back on earth will see time pass quicker, or said another way, it will age more quickly.

If you do this long enough, you could bring the original clock back down, and set it next to the newer clock and compare the two. If you did so, the newer clock, created millions of years after the universe, would actually be OLDER than the universe. It would have seen more vibrations than the original clock which measures the entire life of the universe. How could this be possible?

My first thought is that the original clock, while having emerged at the same time as the universe, is WITHIN the universe and moving around within it. The moment it does so it becomes ensnared in relativity, and ceases to be a universal measurement of the universe (despite having been there from the very beggining).

This seems to make sense, but then here's the question. Can we ever truly measure the age of the universe? Aren't we really only measuring it from a reference frame? What age would the universe be from the perspective of the universe itself, rather than from something (or someone) measuring it from within.

Anyway, Like I said, it's a fairly kooky thought experiment, but it led me to a certain appreciation for the locality of time. It seems, from the way that the "old clock" behaves in this thought experiment that time seems to lose any meaning the moment you take up a position WITHIN the universe. My sense is that time must be the way we experience the difference in the way matter behaves locally within the universe, and that it would cease to exist on a larger (universal) scale.

This really feels like the single dumbest post I've ever written, but anyway there it is

Any thoughts?

 

[darkmatter4brains]

mabus,

This was a great post and not dumb at all.

I believe your correct on the fact that once the clock "enters' the Universe it is "ensnared" into relativity.

The fact that we can comfortably talk about an age of the Universe is tied to the incredible homogeneity of the CMB. What exactly the connection is though, I forget to be honest. Maybe somebody on here can fill in.

 

[SpeedFreek]

If we place the original clock on a rocket, and leave the second newer clock on earth, then the original clock will see time elapse more slowly than the clock back on earth. In other words, the clock back on earth will see time pass quicker, or said another way, it will age more quickly.

If you do this long enough, you could bring the original clock back down, and set it next to the newer clock and compare the two. If you did so, the newer clock, created millions of years after the universe, would actually be OLDER than the universe. It would have seen more vibrations than the original clock which measures the entire life of the universe. How could this be possible?

It is not possible for the newer clock on Earth to be older than the universe as clocks on Earth would be subject to gravitational time dilation relative to a clock in deep space which was away from any gravitational influence.

The original clock, having constantly changed inertial frames during the burn phases of the rocket journey, does not reflect the age of the universe either.

Time passes at its fastest where there is the least gravitational potential. Cosmological time (and the age of the universe) is an approximation, based on a theoretical series of clocks in free-fall across time, under the least gravitational influence in their own epoch, co-moving with the expansion of the universe.

 

[ramparts]

Cosmological time (and the age of the universe) is an approximation, based on a theoretical series of clocks in free-fall across time, under the least gravitational influence in their own epoch, co-moving with the expansion of the universe.

Beautifully put!

 

[mabus]

So basically, if I have it right, no gravitational influence = no time dilation ?
infinite gravitational influence (such as inside a singularity) = infinite time dilation?

 

[SpeedFreek]

In a nutshell, yes. But remember, it's all relative.

I would avoid thinking in terms of "inside a singularity" though. You will either be outside the singularity or outside of the universe!

 

[mabus]

Right

 

[Jerromy]

Excellent topic! The relativity is definitely the cause and the effect, the question as well as the answer.

I doubt anyone can argue that the presumed "age" of the universe is measured in human existence of revolution around our star on Earth at approximately the 20th century AD's experience of a year.

I certainly may be wrong, but I believe that the motion through space itself is what truly does slow down the passing of time. Travelling at the speed of light, time would stand completely still for any atom that could accomplish that feat. Perhaps that is what gives EM radiation the ability to travel timelessly through the universe.

On the other side of that thought occurs to me, would there be a definite "fastest" passing of time? I doubt there is an answer as simple as motionless and unaffected by gravity, one's clock would tick the fastest.

 

[Fallingstar1971]

Very nice indeed.........

IMO the Universe is still only a second or two old. Spacetime is so warped and twisted in on itself, those two seconds have been stretched into billions of years from our POV. But from the outside of the Universe, it was all already over and done a long long time ago.

Star

 

[jff1513]

Very nice question but I think that the problem has to do with second part of the header: "...Absolute Age of the Universe." There is no such thing as an "absolute" age because it implies an absolute time separable from space-time. Both clocks measure time relative to its respective "location" or perspective in space-time. We cannot know the absolute age of the universe, because there is no absolute perspective within space-time from which to measure something that is a quality of the thing being measured, i.e., the universe.

 

[mabus]

An interesting analogy came to me reading some of these responses. Would seem to me that any clock inside the universe measuring time are somewhat analogous to a temperature sensing bouy dropped randomly in a large body of water, like the atlantic ocean for example. They would measure local temperature (or time) as opposed to the "temperature" of the entire body as a single thing.

As SpeedFreek said, we measure the age of the universe as a whole through an aproximation based on "a theoretical series of clocks". Basically we look at the age of random things throughout the universe and estimate it's age based on these individual thermometers (or in this case clocks).

It makes me wonder though. Can the universe have a specific set defined absolute age? Just as the ocean doesn't have a set defined absolute temperature, but rather localized temperatures which we average out to give a combined average on the whole. Don't we somewhat do that with time to a certain extent. Makes me somewhat wonder how far you could carry the analogy between the measurement of temperature and time.

 

[open_mind]

I may irritate a few of the more scientific out there...but I have always believed Time itself is a man made measurement to better explain our own existence but time it self is flawed for it is really only relavent to the space you occupy at the time you measure it and soon as you move the measurement changes...so again just a made up measurement to add value to our own existance for the universe is and thats about all we can be sure of at this point of our development. sorry not a real answer but my feeleing anyhow........peace, -d

 

[Bill_Wright]

This is a great thread and an excellent thought experiment. I tend to side with those who say there is no absolute time therefore there is no absolute age to the universe. Possibly this is even related to the theory that by measuring something you perturb it and that makes the measurement inaccurate. I'd love to get someone like Wheeler or Weinberg comment on this.

Maybe if your first clock was inside of a singularity, therefore outside of the universe, there might be a way to make this measurement. Maybe the LHC crew will come up with some interesting data that provides additional insight into this experiment.

 

[chrisWin]

I have another problem similarly related (excuse pun!)
We have worked out that from our view point the Universe is roughly 13.7 Billion years old . The cosmologists there for tell us we can only study the visible Universe (going back time further we look!) but the Universe is obviously somewhat bigger that the visible hence why we appear to be in the middle of it no matter what telescope is used . Now here`s my problem the speed of light restricts what we see however if the universe started from a single point exploding outwards how does it become bigger than 13.7 Billion light years across as nothing in the Universe can go faster than light ? I know it probably has something to do with time dilation but I`ve never seen anything that explains this and how.
I`m probably showing my igorance but it`s my first time that I`ve registered so am able to post anything could someone with a brain explain in laymans terms how.
P.S I feel like its possibly a daft question from a newbie...

 

[ramparts]

This is a great thread and an excellent thought experiment. I tend to side with those who say there is no absolute time therefore there is no absolute age to the universe.

Hi Bill! I'm glad you side with well-established science Of course there's no absolute time, and therefore no "absolute" age to the universe. When we talk about the age of the universe, as mentioned earlier in this thread, we're talking about the time measured by an observer which following a standard free-fall path through the universe, so something which isn't travelling at significant speeds relative to the expansion of the universe and isn't under extreme gravitational forces (besides those present in the entire universe). Luckily, this applies to most of the stuff in the universe, so this is a pretty accurate way of describing, say, the time felt from past to present by some clump of gas which ends up on the outskirts of a galaxy.

Possibly this is even related to the theory that by measuring something you perturb it and that makes the measurement inaccurate.

That's (sort of) quantum mechanics, which is not at all necessary for these ideas of classical relativity.

I'd love to get someone like Wheeler or Weinberg comment on this.

Thankfully Wheeler and Weinberg have much more important things to do with their time than come on SDC and explain basic physics to people :lol:

Maybe if your first clock was inside of a singularity, therefore outside of the universe, there might be a way to make this measurement. Maybe the LHC crew will come up with some interesting data that provides additional insight into this experiment.

Whoa, there's a lot of speculative (and quite possibly wrong) physics there. "Inside" of a singularity? Well, by definition a singularity has no physical extent, so it's hard to be inside one. And even if you were, there'd be no way of getting the information out. Finally, such a thing wouldn't necessarily be "outside" the universe, and there's no reason to believe that time measured in such a place (again, ignoring the fact that it makes no sense to be "inside" a singularity) would somehow be objective or absolute.

 

[ramparts]

I have another problem similarly related (excuse pun!)
We have worked out that from our view point the Universe is roughly 13.7 Billion years old . The cosmologists there for tell us we can only study the visible Universe (going back time further we look!) but the Universe is obviously somewhat bigger that the visible hence why we appear to be in the middle of it no matter what telescope is used . Now here`s my problem the speed of light restricts what we see however if the universe started from a single point exploding outwards how does it become bigger than 13.7 Billion light years across as nothing in the Universe can go faster than light ? I know it probably has something to do with time dilation but I`ve never seen anything that explains this and how.
I`m probably showing my igorance but it`s my first time that I`ve registered so am able to post anything could someone with a brain explain in laymans terms how.
P.S I feel like its possibly a daft question from a newbie...

Hi Chris - Not a daft question at all! In fact, it's a very common and insightful one Basically the question, if I'm reading correctly, is this: how can the universe be 13.7 billion years old, but bigger than 13.7 billion light years wide, if nothing can travel faster than the speed of light? The answer is that the universe is perfectly allowed to expand at rates faster than the speed of light - in fact, many galaxies are receding from us faster than c. There have been a couple of times in the past when the universe has expanded at such fast rates. This is because while an object (or more specifically, a signal) can't travel faster than the speed of light, objects which move in the expansion are actually at rest relative to the universe. Think about it like this: the important reason nothing can travel faster than c is that if a signal did travel so fast, special relativity tells us it's possible for that signal to travel back in time - a big no-no! But the expansion of the universe doesn't transport signals from one point to another - it actually moves all points away from each other. So - think about this - there's no way to send a signal from point A to point B just using the expansion of the universe, so if the expansion is faster than c, there are no problems.

 

[SpeedFreek]

Finally, such a thing wouldn't necessarily be "outside" the universe, and there's no reason to believe that time measured in such a place (again, ignoring the fact that it makes no sense to be "inside" a singularity) would somehow be objective or absolute.

Bill was I think referring to my comment "you are either outside the singularity or outside of the universe!" which I admit was a little bit glib. What I was really saying is that the singularity is not a part of space-time. If you reach a singularity then your part in the history of the universe comes to an end.

 

[ramparts]

This is true. I guess it's a bit of a misinterpretation to say "oh, just go in the singularity and be outside the universe!" then :lol:

 

[rpmath]

Very nice question but I think that the problem has to do with second part of the header: "...Absolute Age of the Universe." There is no such thing as an "absolute" age because it implies an absolute time separable from space-time. Both clocks measure time relative to its respective "location" or perspective in space-time. We cannot know the absolute age of the universe, because there is no absolute perspective within space-time from which to measure something that is a quality of the thing being measured, i.e., the universe.

The idea of "absolute age" is a big problem for relativity theory...
When relativity was written, scientist believed in steady state universe, but if you can get an absolute age for the universe, you can use it to make a preferred reference frame and hurt the hearth of relativity.

Measuring the cosmic microwave background dipole red-shift, we got we are moving at near 600 km/s relative to that background... may be relative to the big bang? may be our "absolute" speed?
That is near 0.2% of light speed, so the 13.7 billion years age is not affected by that speed (the real age would be 0.0004% shorter, so no visible difference with current accuracy)

 

[joelteply]

6000 years, duh...

 

[Andy99]

Going to be a bit mean here!!

Isn't it ironic that the author of the article spells beginning - 'beggining' - on more than one occasion - so not a typo. Perhaps it depends on which clock you use!!! lol.

 

[Valado]

Great topic. Let me share my thoughts (if incorrect, please help me get out from them).

The term “universe age” depends on what observational point of view inside the universe we use, since time is “relative” from one observer to other. So… ¿does it make sense something called “absolute universe age”, which scientists measure around 13,7 billion years?

To get to an unique “absolute universe age” definition, valid along the total extent of our universe, it must be possible to be calculated, in the same way and getting the same result, from every point and time of the universe, that is, from Earth as well as from any very distant point In the universe (as well as from the most distant point in our universe), and as well as in the past (but, of course, resulting in a minor value). To do so, we must first define what absolute (and locally independent) observational point of view (APOV) should be used.

The best definition for APOV I saw in here is the one ramparts mentioned as “we're talking about the time measured by an observer which following a standard free-fall path through the universe, so something which isn't travelling at significant speeds relative to the expansion of the universe and isn't under extreme gravitational forces”. To me… a very good try. This is almost to say: get a point in the intergalactic medium (no influence of gravitational forces) and motionless with respect to the rubber type fabric of space-time, which is expanding itself.

But, ¿does this point really exist along all the age of the universe?. In our local corner of the universe (here and now) the answer seems to be yes. But ¿is this still applicable to others “heres and nows” of the universe?. ¿Does this make sense in the very-very first stages of the big bang, when gravitational forces, EM, light, matter,… and all the actual stuff we see were in formation phase?.

Let’s go beyond by supposing the answer is “yes”. Then a new question arises. We are able to get a theoretical idea, based on our real knowledge, of how the universe could have evolved in the very small time, let’s say fractions of seconds, milliseconds, etc., from its birth ¿is this time based on our local “here and now” ideal clocks?, ¿would an ideal clock, situated inside that scene and within APOV conditions, measure that very same event time we calculate in fractions of seconds, reaching to the same value? ¿or could it result in a very relevant drift?.

The key point to me is that the APOV defined by rampart suppose that there’s not “extreme gravitational forces” and in the very first stages of the universe everything were extreme, and that scenario is valid for our local corner of the universe. So… seems it can’t be found a valid APOV as a reference to measure the “absolute age of the universe” and I guess our best estimations on this area are based in our local "her and now" which does not stand for some very important stages for the universe. I assume (maybe mistaken) it was calculated putting our local clock in reversal mode and get back “our local time” by using the expansion rate we see from our corner of the universe.

As a final consideration, Quantum theory put us a limit to our capacity to understand the universe. Time is discrete. ¿what about the time “before” when the “absolute universe age” was the Planck time?. In our local corner of the universe that is very small, negligible at all when using our watch time, but possibly it could not be negligible when the universe had that “absolute universe age”. So, there existis a time gap from the universe birth we known it's minimum value, but not any more. ¿how can we measure an "absolute universe age" when we can't identify its moment of birth?.

Thanks.

 

[DavidGriffith]

Which Universe?

 

[ramparts]

Great topic. Let me share my thoughts (if incorrect, please help me get out from them).

The term “universe age” depends on what observational point of view inside the universe we use, since time is “relative” from one observer to other. So… ¿does it make sense something called “absolute universe age”, which scientists measure around 13,7 billion years?

As has been said a few times in this thread, the age which we measure at 13.7 billion years (which you can call absolute if you want, it doesn't really matter) is the age felt by anything which is just "going with the flow" in the universe. If you put a clock in a totally normal section of the universe, it's the time they would measure.

To get to an unique “absolute universe age” definition, valid along the total extent of our universe, it must be possible to be calculated, in the same way and getting the same result, from every point and time of the universe, that is, from Earth as well as from any very distant point In the universe (as well as from the most distant point in our universe), and as well as in the past (but, of course, resulting in a minor value). To do so, we must first define what absolute (and locally independent) observational point of view (APOV) should be used.

The best definition for APOV I saw in here is the one ramparts mentioned as “we're talking about the time measured by an observer which following a standard free-fall path through the universe, so something which isn't travelling at significant speeds relative to the expansion of the universe and isn't under extreme gravitational forces”. To me… a very good try.

Oh, thanks.

This is almost to say: get a point in the intergalactic medium (no influence of gravitational forces) and motionless with respect to the rubber type fabric of space-time, which is expanding itself.

Spacetime is not made of rubber.

But, ¿does this point really exist along all the age of the universe?. In our local corner of the universe (here and now) the answer seems to be yes. But ¿is this still applicable to others “heres and nows” of the universe?. ¿Does this make sense in the very-very first stages of the big bang, when gravitational forces, EM, light, matter,… and all the actual stuff we see were in formation phase?.

A point exactly like this is difficult to find. But most points in the universe are very very close to this. I'll get back to this at the end...

Let’s go beyond by supposing the answer is “yes”. Then a new question arises. We are able to get a theoretical idea, based on our real knowledge, of how the universe could have evolved in the very small time, let’s say fractions of seconds, milliseconds, etc., from its birth ¿is this time based on our local “here and now” ideal clocks?, ¿would an ideal clock, situated inside that scene and within APOV conditions, measure that very same event time we calculate in fractions of seconds, reaching to the same value? ¿or could it result in a very relevant drift?.

The key point to me is that the APOV defined by rampart suppose that there’s not “extreme gravitational forces” and in the very first stages of the universe everything were extreme, and that scenario is valid for our local corner of the universe. So… seems it can’t be found a valid APOV as a reference to measure the “absolute age of the universe” and I guess our best estimations on this area are based in our local "her and now" which does not stand for some very important stages for the universe. I assume (maybe mistaken) it was calculated putting our local clock in reversal mode and get back “our local time” by using the expansion rate we see from our corner of the universe.

Of course the are extreme gravitational forces in the very early universe - and those get taken into account. You quoted my saying "extreme gravitational forces" without quoting the whole thing I said: "extreme gravitational forces (besides those present in the entire universe)". The calculation of 13.7 billion years takes into account anything that exists throughout the universe. It's only things that are localized to one place, such as the gravitational field around the Sun, which will change that calculation. Luckily, nowhere in the solar system will your clocks be significantly changed. But the 13.7 billion years thing doesn't apply to, say, an observer chilling near a black hole.

The key to all of this is the cosmological principle: the idea that the universe is the same in all places. This is clearly not true on small scales (the universe where you are is different from the universe two feet above you), but is on scales greater than a few hundred million light years, where every point actually does look the same. Imagine if you were looking at a slice of the universe from far away, and your computer screen only had pixels representing 500 million light years. Each pixel would look the exact same. Our calculations take into account everything within that framework. Peculiarities beyond that - like the stars and galaxies which form on smaller scales - don't get included in the calculation, but as I said, they very rarely matter.

 

[mabus]

Spacetime is not made of rubber.

I'm sorry but, I thought this quote was just AWESOME. If we ever put up a "best quotes" section this is my nominee :lol: