Bizarre theory suggests time may be running out (2007)
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However, the approach of taking another look at our assumptions to explain the 'expanding' universe makes my brain very happy.
So the story has me quite torn ;)
I originally arrived at the line of thinking via the measurement question - is anything in the universe at an unchanging distance from anything else? (According to expansion theories, anwyay.) If that's the case, would it not be possible to measure the wavelength of the light reaching relatively-fixed object A from its counterpart object B? If the red shift still occurs, then we know time is slowing down. If not, then expansion wins.
Expected problems for this measurement would include scale (if chemical bonds are the only distances in the universe that don't change, how do you measure the wavelength from one atom to the next?), and more scale (would the change be measurable on a scale smaller than intergalactic?). Oh, and the original assumptions. Those might be a problem, too. (That something (anything) is fixed, and that my mental model is not orders of magnitude oversimplified).
That's a timely remark ;)
Check out the Friedmann equations for average density of the universe.
The AstronomyCast podcast (http://www.astronomycast.com/) has a fairly good explanation of the expansion of the universe in several episodes. Don't recall which episode, but I'd try ep. 5 and 6 (on the Big Bang) or 11 (Dark Energy). Actually, I'd recommend the whole show.
So what does it mean for time to take time?
I have a similar problem with the idea that time has somehow started to exist as the whole concept of starting depends on time.
What does it mean for length to take length?
If space expands doesn't that mean that a meter gets "longer"?
In general relativity, "time" plays several different roles, and you need to be more specific about which one you're talking about. You're usually talking about either proper time, which is the spacetime distance measured along a timelike curve (and also, up to a sign, the actual stopwatch reading you'd obtain by traveling that curve), or the coordinate time, the direction in spacetime that's the odd man out and has the "wrong" sign in the metric signature. This second definition (coordinate time) is wiggly, because there are infinitely many coordinate systems that you could pick to describe the same spacetime, each of which will use a different definition of coordinate time, and general relativity's main insight is that all of these coordinate systems are equally valid (actually, it says that the equations describing spacetime don't even change when you switch coordinate systems, perhaps one of the most profound discoveries in all of physics - if you add in the observation that curvature is caused by matter, you have almost enough in those two observations to construct the entire theory of general relativity from scratch).
Any physicist working in the field is intimately familiar with the subtleties here, and certainly knows that "clocks run slower" is a meaningless statement unless you're talking about speed relative to some other measure.
The gist of how time could run at a different speed is that if the time component of the spacetime metric was halved along your path, your stopwatch would tick off half as much time as you'd expect it to. But that's a very artificial scenario, because it presumes you have the original unaltered metric to compare to, which you don't. Locally everything would seem normal. Figuring out the global consequences of a decaying timelike component in a realistic metric is a decidedly nontrivial task, and from what I gather, that's what Senovilla is making a claim about, apparently involving string theory, as well.
Re: time starting to exist, the idea there is that if we follow a timelike geodesic (i.e. a spacetime path that matter can travel on) far enough back, we'll find that at some point the sign of "time" switches, and stopwatch readings would return negative numbers and other such nonsense. Time would "start" at the first point along that curve where a normal timelike component existed in the metric. So the more accurate statement would be that time in the spacetime metric started to exist at some point earlier along the backwards continuation of the line that we currently think of as time (though it measured no such thing before that point), which is a far more sensible thing.
It seems to me that what's happening is that physicists have created models that can be shown to work for certain parts of reality. That is, they can be applied with predictable outcomes in the real world.
The same models also have extreme states, where some variable switches sign or some function curve changes directions. And now they're asking, what would be the effects in the real world at these inflection points of the model?
It could well be that the model simply stops working at these points, like a variable representing the height of a person stops working once its value turns negative. It could also be that the model does work, but the semantics used for its popular description stop working.
To give you a sense how bad it gets there, string theory results and arguments have to be "popularized" to an almost meaningless level just so that theoretical physicists that don't work in string theory can understand them, just because the whole field is so young and complex; filter that once more through a journalist, and you can end up with some pretty wacky claims, even if they're completely true.
I'd make no specific claims as to whether this research means anything or not, though; it's a famously speculative field, with only the barest of observable evidence to go on, and effects from pretty much every length and energy scale factor crucially into any cosmological evolution, making it all but impossible to say with any certainty that one proposed solution is better than another. This is where you start to get people arguing in terms of symmetry and beauty rather than observation, which brings physics awfully close for comfort to philosophy...
Anyway, assuming this is true should be an interesting thought experiment. If time is slowing down universally we shouldn't notice a difference (relativity). The suggestion seems to be that time is going slower in our older part of the universe than it is around the "edges". Making it seem to an observer in an older part like the expansion is going faster and faster, despite the fact that no energy is being added. This also seems to suggest there should be (even older) parts of the universe for which the perceived acceleration is negative. I wonder whether that's the case. A tricky bit is that if they are in fact moving towards us and we're moving away from them at a faster time pace, they would still appear to be moving away from us at an accelerating rate.
Another question is what would be the difference between those parts of the universe. One might argue that the older galaxies that have attracted more time-slowing mass, but that's shaky. Another idea might be that the speed of time is driven by the amount of active energy itself. Perhaps a new definition of entropy would help us there.
Hoping to hear more.
At an atomic/particle level, movement (speed) is related to temperature. If something reached 0 degrees Kelvin, there's no particle movement at all. You could argue that since time is relative to space (as opposed to an independent variable), time would slow down as temperature goes down. If the whole universe is cooling, maybe time is slowing down.
Source info: http://en.wikipedia.org/wiki/Thermodynamic_temperature
Which is sort of a backwards way of saying that General Relativity actually talks about the relationship between speed and time, saying the faster an object is going, the slower (in a sense...) it is travelling through time.
If this explains why we feel time going faster as we get older, wouldn't that imply that our soul is based in a non-physical dimension?
http://www.wolframscience.com/nksonline/page-481?firstview=1
As for measuring time acceleration, perhaps comparing time on earth to time on the event horizon of a black hole and seeing if they deviate by a different amount than predicted by the present mathematical models it would be useful for uncovering any acceleration of time. Assuming the acceleration of time was exponential then the slowing of time on the event horizon would lead to a different rate of acceleration than on earth. Evidence of that difference could prove the theory.
Yes/no? Thoughts?
From what I can understand, it reminds me of the Richard Feynman's QED theory where he says vacuum is not really empty but particles with opposite charges get created and nullify each other in a short time.
Forgive me, i may be naive.
Time "exists" as a result of measurements of the Earth's rotation. That's how 'universal' it is. Hmmm. Maybe it's speeding up, like a film. Maybe that's why the 'universe' is accelerating. Or maybe it's moving with a sine-wave motion ... which explains why I'm feeling dizzy.
edit: also the headline seems a bit over-dramatic it's not running out it's slowing down.
Time slowing seems like it'd be asymptotic. You should be able to have an arbitrarily large time t, where time is flowing at rate r > 0. According to my calculations, anyway. (Along the lines of: "shit, I really don't want time to stop.")
Good point. Time is only relative. I'm not sure if there would be any nasty (human) consequences to time going infinitely slow. It's still going at the same pace for the observer.