Time Dilation

Ever since I was introduced to the Theory of Relativity, I've always been hung up on time dilation. It makes zero sense to me why a constant speed of light has any bearing on the passage of time whatsoever. So, can someone please explain to me why the passage of time slows as one approaches the speed of light according to a mechanical clock. Every example I've seen explains the phenomena using a clock made of light bouncing between two mirrors. Well how convenient for them. I understand geometry, so I get why this particular clock would be fooled into thinking time has slowed down. But why would a wrist watch tick any slower as it speeds up? Thanks!

From my understanding, BlueLogic, it's a matter of atomic decay. Yes, it's not actually based on a mechanical clock, it's based on the rate of decay at the atomic level. Your atoms age faster or slower depending on speed and gravity.

Maximized can probably give you more detail and may, in fact, prove me wrong there.

Max?

Thanks for the response!  It prompted me to continue my search armed with the "atomic decay" key words.

I found this: http://askville.amazon.com/Time-dilation-explanation-equations-kind-abstraction/AnswerViewer.do?requestId=33707050.

The OP asks a question similar to mine and an in answer someone mentions an experiment measuring the atomic decay of atoms that were sent away and flown back.  

Another respondent gave perhaps the most satisfying answer I've heard yet.  It made clear to me that it is not the speed that slows time, but rather the acceleration.  That, I feel, is a breakthrough because every time I heard "speed" my brain screamed, "relative to what???" Acceleration is without respect to another frame, so that helps. I'll have to chew on that awhile.

Also a respondent tried to explain the phenomenon as a push/pull between space and time where time is best thought of as a fourth dimension of space.  As one accelerates, width contracts giving way to a stretching of time.  Another abstraction of sorts to chew on.

The most, and least, useful response implored the reader to give up the intuitive notion of a universal clock.  All frames of reference (objects motionless relative to each other) have their own clocks.

Utterly mind bending. But I feel closer.

Any further input or clarification would be greatly appreciated!

Yeah, I was also terribly confused by that for a looong time. And I especially thought the same way as you about that light clock. Seems rather convenient to use a clock that uses light signals as a measure of a time duration. What about the general case, or just the case of a mechanical clock?

What's happening is this:

To your clock, time is running at a 'normal' pace. Just as it would be for you, while looking at the clock and traveling at relativistic speeds. And it's like that for everyone else, and their own clocks, everywhere, traveling at whatever speed.

So what's time dilation then?
It's when someone with a speed different from yours is watching your clock work. When watching you, to them, your clock will appear to be moving slower than their own. But that's not all. I wrote "speed different from yours". What about them? Isn't from your point of view, their speed relative to you, different to your own, too?
It is! And so, if you were to look at their clock, and compare it to yours, theirs would indeed be moving slower compared to yours now! That's one example of what is meant when you hear the phrase "everything is relative". There is no absolute frame of reference, or, your position and their position, or your clock and their clock in Relativity. There's only your clock compared/relative to their clock. That's what counts. And both of your clocks will democratically slow down to the other. (This is btw part of one of Einstein's two hypotheses: that every 'inertial system' -- let's call it frame of reference -- is equivalent)

But again, your own clock won't be slowing down to you just because you are traveling at some speed -- which, again, is meant as a speed relative to someone or something. Because it'd never be working reliably...there's always something moving relatively to you!  

So much for your clock not actually working differently.

As for why fast traveling clock slow down at all?
Now that has to do with the speed of light being finite, and equal in all reference frames. What does that have to do with time?
Well that's indeed a bit difficult to actually explain without getting lost in the technicalities. Aaaand Imma be honest and say I don't know how. The best I can say is: you measure speed usually in <distance>/<amount of time passed>. And if you want that velocity to be the same in any case, the <amount of time passed> has to change with the <distance>.

If it cheers you up, here's a funny consequence: for light itself, time doesn't pass. You could say light doesn't age.

But to not bash the beloved light signal clock:
The idea of that model is to demonstrate that if you just use light to measure the passage of time -- and assume that it has a finite speed in your frame of reference -- which you can legitimately do, as it's finite and constant, you get that moving objects' 'seconds' take longer than your own. And the way the dilation appears is due to the speed of light having the same constant value in all reference frames.

But at the end it doesn't matter what clock you use, because all of them just measure a passage of time.

TL;DR: your mechanical clock doesn't slow down. At least not to you, only to everyone else moving at a relative speed, different from yours.

__________
EDIT: Argh...and now I've spammed the thread with what you already read in that other place. Oh well...had fun writing it though.

See? Max made far more scientific sense than I did.

Wow, thanks for all the effort! I appreciate it.  

Reading your explanation, after also reading the page I linked, it seemed to make more sense now than it would have before. My big breakthrough I think will be eventually coming to grips with the notion that there is no universal clock. Or that, if there is, none of us has access to it. Also that time is not separate from space, but both are a part of something else. Rereading that sentence, and then hearing a voice in my head tell me, "that's why it's called space-time moron", is rather humbling. :)

So...time is not universal. Yeah, that's going to take a while to swallow.

Thanks again for the help folks!!

Exactly Blue. And sorry I couldn't give you the whole picture.  

We all (very likely, and in a good approximation) live in a four dimensional spacetime, where time is an actual dimension, just like our three dimensional space. Only, it's a special dimension.

And a final fun fact (cuz I love em): In Special Relativity's spacetime we always move with the speed of light, no matter what our speed in 3D space is. So you see, our velocity always distributes between a velocity in the time direction and a velocity in the space direction.

Hmmm, come to think of it...this IS a good way of handwaving the answer to the question:
Why does someone's time seem to slow down when they're going fast?
It's because they're using up all their speed in the space direction, so they have less for for time!

What if I told you there could be 2 time dimensions

MaximizedAction wrote:Exactly Blue. And sorry I couldn't give you the whole picture.

Oh it's certainly not your fault.  Some ideas are so basic to my vision of the world that I don't even know how to properly question them.  Much less, can I understand the answer when I hear it.  

MaximizedAction wrote:...Hmmm, come to think of it...this IS a good way of handwaving the answer to the question:
Why does someone's time seem to slow down when they're going fast?
It's because they're using up all their speed in the space direction, so they have less for for time!

*brain explodes*
Wait, no that actually makes some sense.  Hmmm, I'll read up on the subject.  Thanks!!  

EDIT:

Norlond wrote:What if I told you there could be 2 time dimensions

...Oh, string theory...mmmhmmm.  Multiple dimensions of time...ahhh, mmhmmm.  Time moving sideways...I could see how that...right.
*begins mumbling to himself occasionally giggling for no apparent reason*

So if I achieved the speed of light my mass would be infinite    I would be everywhere in the galaxy? of course a force to move such mass would have to be infinite as well. what would be the Time Dilation when your everywhere?

Don't want to be everywhere at once, it makes you 'evolve' into a newt.

Just look at a photon, they travel at the speed of light (obviously), and they don't experience time, because time dilation is infinite in that case

You wouldn't be everywhere at once tho, speed of light isn't infinitely fast, going from one end of the milky way to the other would still take 100,000 years ;)

STOP right there, criminal scum! You violated Lorentz invariance!

None of you will ever become a photon because, unlike the photon, you aren't massless.
And I mean "invariant mass", not the kind of mass that you often see as E=mc^2, that mass isn't a constant, better call it energy.

The model is this:
massless things, like the photon, don't experience the passage of time from their point of view.
massive things, like baryonic matter, like you, do experience a passage of time.

But you'll never be able to boost yourself from one state of existence into the other: you'll never be massless/going with the speed of light, just like the photon will ever experience time or slow down.

So how was Nor's post wrong? Technically, not at all because he was talking about photons.

I just think that comparing a fast prettz to a photon is a potential source for confusion. Like for example, no matter how close to the speed of light he gets, he will still experience the same passage of time from his point of view, and he ESPECIALLY won't start being everywhere at once in the universe. Simply because his mass is constantly non-zero, no matter how fast he goes.


I mean, comparing the two is a bit like describing oranges with apples; at some point you just might get confused about some things...

MaximizedAction wrote:Not quite...
[post under construction]

Yeah, yeah, I know. It's too simplified. Max-senpai of course isn't satisified with simple answers. I'm too silly.

must be time to make a brew.

Norlond wrote:

MaximizedAction wrote:Not quite...
[post under construction]

Yeah, yeah, I know. It's too simplified. Max-senpai of course isn't satisified with simple answers. I'm too silly.

Hey hey, I didn't say you were wrong!

RavenEyry wrote:Don't want to be everywhere at once, it makes you 'evolve' into a newt.

I only saw that episode the day it aired that is more then 10 years ago... so how the heck do I know your talking about star trek voyager   

MaximizedAction wrote:
I just think that comparing a fast prettz to a photon is a potential source for confusion. Like for example, no matter how close to the speed of light he gets, he will still experience the same passage of time from his point of view, and he ESPECIALLY won't start being everywhere at once in the universe. Simply because his mass is constantly non-zero, no matter how fast he goes.

this topic seem fun so I wanted to add to it, I brought the "every where at once" cause I heard mass expands the faster you go.

Prettz wrote:

RavenEyry wrote:Don't want to be everywhere at once, it makes you 'evolve' into a newt.

I only saw that episode the day it aired that is more then 10 years ago... so how the heck do I know your talking about star trek voyager   

It's so hilariously awful you never forget

Prettz wrote:this topic seem fun so I wanted to add to it, I brought the "every where at once" cause I heard mass expands the faster you go.

That's correct as long as you call mass the m in E = m c^2. There m is actually
m = m(v) = m_const/squareroot[1-(v/c)^2],

with v as the speed of the object being measured and c the speed of light. m_const is then this constant mass I mentioned.
Here you can see why, the closer v gets to c, you're getting something that approaches ~1/0, so, infinity. Which is also why they need higher and higher energies at particle accelerators to get massive particles closer and closer to c.

What might also be worth emphasizing is that E(v), and thus m(v), is what someone measures, to whom you appear to have the speed v.
Since to you your v=0, you'll also have m(0)=m_const. So to you your own energy, and thus mass, is always this constant one.

Btw, regarding time dilation, you can swap m_const for <your time that passed on your clock for you>, and E for <time measured by someone else> and get the exact same story for time dilation.

Sorry for the formulas but that way it's less walls of text.