Given Einstein’s proof that time is relative, we can only not the differences in the time of events (eg. muon decay or chemical reactions) between different frames of reference. There is no “proper time”, or time with refernce to the stars. My question is this: as the universe expands, the average density of matter is continually dropping. Hence, the gravity -induced distortion of time should be slowing the rate at which time passes. Is this testable?
It’s sort of meaningless, as I see it. There’s really no such thing in GR as elapsing time. There’s just a 4-manifold with a locally-Minkowskian structure on it. All world-lines of particles have squared 4-velocity -1, everywhere. To say there is no “proper time” is misleading: there is a “proper time” along every world-line. What there isn’t is a universal standard of time.
I have evidence that the opposite is true! Simply witness how quickly the time I have to finish my term papers passes as the time they are due approaches!
How would we know? Can you think of an experiment that would determine this?
Actually, there is proper time. In the reference frame where two events happen in the same location, the time elapsed is the proper time. It’s the shortest time interval you can measure between those two events, in any reference frame.
If time is slowing in the Universe, what is it slowing relative to?
There is nothing outside the Universe (or at least as far as we’ll ever be able to ascertain) therefore whether time in the universe is slowing or is not only impossible to know, it is a meaningless concept. Something can only change speed relative to something else. There is no “something else”, therefore time cannot change its speed relative to it.
Now if you want, for the sake of argument, to step outside the Universe for a moment, you are then in a whole other place where time doesn’t apply. How then can it have a speed that in anyway can be compared to you?
So I guess the answer is no.
I would say not, even if it were we would have no way of measuring the rate of slowing as we are in the same reference frame we would have nothing to measure against.
Take for example the twin paradox of special relativity for the twin (A) who travelled away from earth at a velocity that is a high fraction of c time travels slower relative to his twin (B). For twin A less time has elapsed relative to his brother, but for each twin time would have appeared to run “normally”, i.e. their perception of time elapsing is unaltered.
Therefore without a second frame of reference we cannot determine the difference between the two, even then we would only have the relative difference between the two frames.
Hope this makes sense, I have a feeling that my sentence structure and explanantion is a bit naff.
[Complete hijack] ralph124c, why do you frequently capitalise a single WORD in your OP titles? It’s only very vaguely annoying, so doesn’t warrant a pitting, and I don’t have a problem with you otherwise. [/hijack]
It is a tricky concept, but consider the following thought-experiment: We iknow that in AD 1965, the solar muon lifetime is X microseconds. We measure the same lifetime in AD 2004…and find that the muon’s lifetime/time to decay is now 1.2 X (x).
Would this prove the assertion that time is slowing down?
In fact, can we project a time (after the starts have all exhausted their fusionable materials), in which the time interval between events would become infinitely long?
If we assume the “speed of time” is changing as you suggest, then the tools we use to measure that time interval will change as well by the same amount.
In your example, whatever method or mechanism or logic we used to determine the decay interval to be x microseconds in 1965 would still produce the same measured result today. If, as Futile Gesture pointed out, you had a way to measure time passage using tools completely divorced from this Universe, well then yes, you might be able to detect a change if one existed.
But absent that, your “ruler” is shrinking/stretching at the same rate (and for the same reason) as the thing you’re measuring. So you won’t detect a change.
Could all proper time intervals in a given metric be said to be, on average, increasing or decreasing in length depending on the average curvature of that metric? If a universe gets flatter, is the average proper time interval getting longer, for instance?
As I understand it, I don’t think it would work that way. Muon decay would remain the same. If length got stretched, rather than time, everything in the universe gets stretched. 1 foot rulers are still 1 foot rulers, and we have no way to observe that 1 foot used to be shorter than it is now.
I think. This is NOT my area of specialty. By a longshot. I’ll have to ask my cousin, Osu Mercotan. He got his doctorate in Physics.
Nope, TIME has published weekly since 1923, and shows no sign of slowing down. <Reads OP and thread> Never mind.
Suppose you use the following “yardstick” to measure time: the rioactive decay of radium: you know the deay of radium results (on avarage) of so many alpha particles/microsecon. This decay rate is not affected by the frame of reference-would this not be measurement in accord with “proper” time?
Oh god, my head hurts.
It puts the lotion on its skin…
[ps]I’m not sure why I wrote that. I’m not drunk or anything, but it popped into my head[/ps]
But how do you measure a microsecond? You said time has slowed down, which means the time of the decay **and **the time you measure. It just cancels out and there is no way of knowing.
Besides, what is time? How does it “slow down” anyway? You perceive time as “moving” in some direction, but that’s just your perception. The “speed” of time is really just a construct of the human mind.
It could be a stupid question, I don’t know.
And how is your microsecond measured? How do you then ensure that the length of your microsecond doesn’t change? Are you using a quartz timer? What’s stopping the quartz vibration slowing? Maybe you’re using the decay of some other material. How do you know it’s not slowing too?
Playing around with radioactivity or any other other ‘natural’ timer isn’t going to solve anything. If it is within the universe then it is equally affected by any ‘slowing’ of time. End result; no noticable difference.
But, not matter. I say again; the concept is flawed. Time in the Universe cannot ‘slow’ because it has nothing to slow relative to. It cannot slow compared to ‘proper time’ because there is no such thing. Everything is relative.
It’s worth repeating that; everything is relative.
After drawing a few pictures, I’ve concluded it is a stupid question. Never mind.
I don’t care about TIME, but I do hope that Playboy doesn’t slow down. I think it should speed up, actually. It should become a weekly!