# Does My Wrist Watch Physically Beat Slower?

1. Dec 23, 2012

### Kingfire

Hello,

Some physics books tend to say that "your wrist watch will be beating slower when you travel at the or close to the speed of light." Does that mean literally?

My own speculation:

Although time does slow down when I travel at a speed close to the speed of light, my wrist watch will not beat any faster or slower because it is just a mechanical device that beats every earthly second.

I am not sure though.

2. Dec 23, 2012

### ghwellsjr

In the Inertial Reference Frame (IRF) in which the earth is at rest (we treat the earth as if it were all by itself, not orbiting in a solar system), clocks that are at rest on the earth tick at the same rate as the Coordinate Time of the IRF. Clocks that are moving tick more slowly in the IRF. So if you are traveling "at a speed close to the speed of light", then you are experiencing Time Dilation meaning your clock takes longer to beat an earthly second than the earthly Time Coordinate of the IRF.

3. Dec 23, 2012

### HallsofIvy

First wrist watches don't beat! What relativity says is that your wrist watch will run slower, your pulse will be slower, you will move slower, as observed from a frame of reference with respect to which you are moving. Of course, from your point of view that person observing you is moving with respect to you and so you will observe his watch running slower, his pulse beating slower, etc.

Yes, this is a "real" result. It has been, for example, experimentally verified that elementary particles that are moving fast with respect to the laboratory have longer lifetimes than those that are stationary with respect to the laboratory.

4. Dec 25, 2012

### bobc2

O.K. so far.

ghwellsjr, not to sound critical, rather just to point out how careful you have to be with the language when communicating this. I know what you mean by your statement and understand it just fine. The moving observer has the experience that nothing unusual is going on with the tick rate of his clock. His proper time is ticking away the same as everyone else's proper time.

Being a little more careful you might not want to say that the moving observer has the experience of his clock ticking more slowly than the IRF.
The moving observer would actually have the experience of observing the IRF clock to tick more slowly than his own. Each observer has the experience of the other's clock ticking more slowly.

Again, I know the correct meaning you were intending and was just trying to make sure your meaning was understood by Kingfire.

Last edited: Dec 25, 2012
5. Dec 25, 2012

### bobc2

Kingfire, there are at least two different competing interpretations of special relativity on this forum.

1) First, there is what is known as the Lorentz Ether Theory (LET). If you are basing the answer to your question on this interpretation, the answer to your question would be, yes. Yes, your watch physically beats slower. That's because, according to LET, there are time shifts in the transmittal of electrical forces between and within physical objects, resulting in actual changes in speeds of physical interactions, including clock mechanisms (affecting tick rates, etc.).

2) The other interpretation of special relativity is based on the Minkowski 4-dimensional spacetime representation. In this view there is no intrinsic change in clock tick rates. However, different observers (moving relative to each other) live in different 3-D cross-sections of a 4-dimensional universe. We will refer to these as different hyperplanes of simultaneity. If clocks are modeled as 4-D objects, then different hyperplanes of simultaneity will cut across a 4-D clock at different points along the 4-D worldline of that clock (different time points). Thus, different observers will in general read different values on that clock.

These brief comments do not really give you the story, but if you are interested there are those here who could explain this with more clarity and detail.

The hyperplanes for a blue and red observer correspond to the blue X1 axis and the red x1 axis. Three observers pass each other at event A, and each has a different reading for a clock that is at rest in the black inertial reference frame. Each observer is moving along his own X4 axis at the speed of light.

Last edited: Dec 25, 2012
6. Dec 26, 2012

I don't think Einstein ever intended his Special Relativity theory to apply to the real world. He was proposing an idealised world where things did not obey the laws of nature. He postulated a. A world where matter moves in perpetual motion and b. a world where the speed of light is a constant. From those (and other) imaginary scenarios he worked out a system. Sort of like the computer world 'Second Life'.

We all know that is not the real situation. Clocks keep the same time everywhere and no one moves in perpetual motion.

7. Dec 26, 2012

### Staff: Mentor

8. Dec 26, 2012

### Staff: Mentor

I'm not sure that's relevant to the OP, since all of the competing interpretations make the same predictions for all experimental results, including those having to do with time dilation.

9. Dec 26, 2012

### ghwellsjr

Yes, that's why I first said (and you agreed with me), "Clocks that are moving tick more slowly in the IRF", which is another of saying, "clocks that are moving are experiencing Time Dilation". When talking about the observer moving with the clock, are you only going to agree if I say "observers that are moving tick more slowly in the IRF"? People don't tick so I used the equivalent statement, "experiencing Time Dilation". Since both the observer and his clock are experiencing the exact same Time Dilation, the observer's subjective perception of time agrees with his objective observation of his clock. No one is ever aware of the Time Dilation of any clock, not his own or any clock moving with respect to himself.
No, it's not, unless you can find an IRF in which he and everyone else are traveling at the same constant speed.
Apparently you do not know the correct meaning I was intending based on your re-interpretation. The moving observer would not actually have the experience of observing the IRF clock to tick more slowly than his own. There are so many things wrong with your statement. First off, I never referred to an IRF clock--there is no such thing. Maybe you thought I meant a particular clock that was stationary in the IRF.

That brings me to the second wrong thing. As I said before, no one can ever observe the Time Dilation of any clock, let alone "actually have the experience of observing the IRF clock to tick more slowly than his own". I have no idea what you mean by that or why you would think that is what I really intended to say.

Finally, your statement that, "Each observer has the experience of the other's clock ticking more slowly" is so wrong, as I've stated repeatedly.

So I hope Kingfire understands the correct meaning that I am trying to convey and not your incorrect re-interpretation.

Last edited: Dec 26, 2012
10. Dec 26, 2012

The math.ucr.edu site is a great mine of information - thanks.

Oddly no experiment verifies (nor could verify) perpetual motion and a constant speed of light yet these are, as I mentioned, cornerstones of Special Relativity.

The other stuff about Time Dilation and Keating Hafele is not really relevant since it involves acelerated travel.

11. Dec 26, 2012

### HallsofIvy

I'm not sure what you mean by "perpetual motion" as a cornerstone of Special Relativity. The fact that there is NO "perpetual motion" is a matter of the laws of thermodynamics, not relativity.

12. Dec 26, 2012

### Staff: Mentor

The Michelson-Morley experiment doesn't count?

13. Dec 26, 2012

Michelson Morley was not about whether the speed of light was constant. They wanted to see if light travelled the same distance in the same time despite the orientation of the path.

14. Dec 26, 2012

### bobc2

I don't understand why you have to interject that esoteric philosophical commentary. On the contrary, Kingfire specifically wanted to know if it is literally true that clocks tick more slowly.

Kingfire: Some physics books tend to say that "your wrist watch will be beating slower when you travel at the or close to the speed of light." Does that mean literally?

What do you think he meant when he asked, "Does that mean literally?" So, why is it so important to avoid answering the question Kingfire is obviously driving at?

So, why put the standard operationalist spin on the topic? Why all of this elitist attitude on the forum (Kingfire knows that watches don't "beat" like a clock, so why would anyone have to belittle him over that subtle point?). Lorentz Ether Theory is not at all equivalent to Einstein's special relativity (except for philosophical operationalists who insist on avoiding any reference to physical objects and processes).

Lorentz was intent on providing a quite physical explanation that casts physics in the context of a physical 3-dimensional world evolving in time, explaining constant speed of light for all observers, length contraction and time dilation explicitly as resulting from considerations of transmittal times for forces between objects and within objects. How you can say that is equivalent to Minkowski's geometrization of special relativity just doesn't seem logical. Equivalent outcomes of particular calculations do not eliminate the significance of the difference between the fundamental concepts underlying LET vs. Einstein-MInkowski.

What do you want from physics--the elimination of any discussion or recognition of the historical development of LET and of Einstein-Minkowski special relativity? Should this be allowed only within the university philosophy departments? What a corruption of physics and its pursuit of the description and understanding of physical reality!

You think only the time dilation and length contraction calculations matter--and they come out the same for both LET and Einstein-Minkowski? Try developing the concept of a 4-dimensional curved spacetime from LET. Einstein said essentially that he would not have gotten anywhere with general relativity without Minkowski's 4-dimensional spacetime of special relativity. Oh--but Einstein shouldn't have done it that way--that's just philosophy!

Last edited: Dec 26, 2012
15. Dec 26, 2012

### Staff: Mentor

And traveling the same distance in the same time doesn't equate to the speed being constant?

16. Dec 26, 2012

### Staff: Mentor

Because it doesn't have a well-defined answer. What does "literally" mean? What rule do I use to tell me whether the watch is "really" beating slower or only "appears" to beat slower? There is no unique rule for doing that. There is a unique set of rules for predicting actual observables, but Kingfire's question, as far as I can tell, isn't about actual observables. Perhaps I'm misunderstanding the question; if so, it would help to re-state it in a way that makes clear that it *is* about actual observables.

Because it focuses on questions we can actually give answers to, instead of questions where we just go round and round about philosophy and never reach any resolution.

See, here's the thing: you think that "physical objects and processes" has some well-defined meaning independent of the experimental results that tell us *what* physical objects and processes there are. Theories about such things are worthless without experiments to back them up. If experimental results are consistent with more than one interpretation in terms of "physical objects and processes", then the correct answer is that *we do not know for sure* what physical objects and processes there are. I would rather just admit that openly.

Such discussion is fine, but it's not physics. It's the history of physics. The two are not the same.

17. Dec 26, 2012

### arindamsinha

Think about this - if the wrist watch does not get any slower, what does "time does slow down" mean? (This is all compared to someone who is not traveling, of course, as the person with the traveling wrist watch has no means of detecting this.)

18. Dec 27, 2012

### HallsofIvy

What do you mean by "every earthly second"? That's the crucial point!

19. Dec 27, 2012

### Vandam

Are you telling us here that Einstein's SR didn't contribute anything to physics, but a lot to philosophy?
I explained you elsewhere what Einstein did for physics as far as the Lorentztransformations mations are concerned, but you stay stuck to your calculator. Physics is more than mathematics. But you refuse to accept that.

20. Dec 27, 2012

### The Jericho

George Wells from Bishop's Stortford?