Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: lunar11 on 29/03/2012 22:29:46
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Special theory of relativity states that 'moving clocks run slow'.
I can appreciate this but what I would like to know is, do the mechanism of the clock actually slow down?
If the clock slows down then don't the specification of the components have to be changed.
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Special theory of relativity states that 'moving clocks run slow'.
I can appreciate this but what I would like to know is, do the mechanism of the clock actually slow down?
If the clock slows down then don't the specification of the components have to be changed.
Yes. The mechanism, regardless of what that mechanism is, slows down too. The mechanism could be a spring, a quartz crystal, whatever. The specifications of a clock are defined in the rest frame of the clock and as such are unique. You could specify them from another frame and get it to run at the same rate a clock "at rest" runs then they will run at the same rate. However the clock "at rest" will run faster.
Here is how to construct one example of an ideal clock.
http://home.comcast.net/~peter.m.brown/sr/light_clock.htm
In this clock we use the speed of light which is postulated to have the same value in all inertial frames.
Best wishes,
Pete
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You are thinking wrongly because most people do not describe this process fully and correctly Clocks where you are always run normally and time seems to flow perfectly normally whatever speed you and the clock together are moving at however if you and the clock are moving very fast relative to someone else the person who is watching you and the clock zip by at high speed sees your clock moving slower than you would.
The correct statement is that moving clocks run slow when observed from a distance by someone who is not moving, but they continue to work normally for someone who is moving with the clock.
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Special theory of relativity states that 'moving clocks run slow'.
I can appreciate this but what I would like to know is, do the mechanism of the clock actually slow down?
If the clock slows down then don't the specification of the components have to be changed.
It seems to me that you might be thinking that speed mechanically affects the internal mechanisms of clocks. Actuality that's true. But you have to keep in mind that it affects all clocks the exact same way. E.g. suppose you and the clock are initiallt at rest in the inertial frame S. You then change your speed such that your new frame of reference, which we'll label S', are in relative motion. Once again we would detect the clock in frame S running slower than clocks at rest in frame S'. Rember that there is no such thing as a frame of reference whose velocity is absolute zero. All inertial frames are equivalent.
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You are thinking wrongly because most people do not describe this process fully and correctly Clocks where you are always run normally and time seems to flow perfectly normally whatever speed you and the clock together are moving at however if you and the clock are moving very fast relative to someone else the person who is watching you and the clock zip by at high speed sees your clock moving slower than you would.
The correct statement is that moving clocks run slow when observed from a distance by someone who is not moving, but they continue to work normally for someone who is moving with the clock.
precisely.
In fact, I will add that the effect of dilated time and whose clock is now running slower is completely relative - meaning that the man moving with the clock will perceive the world around him to begin moving a lot slower, but to the stationary observer, the moving clock is the one which is experiencing a slowed down effect.
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The best explanation of this phenomena I ever read was this: Time is a dimension like the three spacial dimensions we normally think of.
If you and I are sitting next to each other we are moving together through time at the speed of light. To move through space we need to use some of our velocity through time. So if I get up to walk away from you, I'll use a tiny bit of my velocity through time to move through space. This means that I'll age just a bit slower than you do. The faster I move through space the slower I'll move through time. Clocks run slower because time itself runs slower, or more precisely you are moving more slowly through time.
Clocks don't REALLY measure time in the same way that a speedometer measures speed. A clock is just a machine that moves in a precise way so that it makes one revolution in a given period.
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Or maybe, that your 'time'' is there with you, always of a same measure, any time dilation becoming your comparison between frames of reference. But you need to add to that that under certain circumstances, as in the twin (thought) experiment, time dilations must have measurable consequences. You can also think about the way NIST has proofed time dilations (gravitational) on Earth to see that even though we constantly can find other clocks to move slower, or faster, than ours we find no problems living under such circumstances.
Time seems very much a geometry to me.
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Time seems very much a geometry to me.
Whereas gravity is warped space-time. Time appears from space warped by gravity. Both can be thought of in terms of geometry.
Mass tells space-time how to warp. Space-time tells mass how to move.
Mass tells space-time how to warp. What we tend to forget is as space-time warps, clocks run at different speeds as observed by distant observers.
Space-time tells mass how to move. Again, we tend to forget that in moving it's not just through spacial dimensions and time but that time in warped space-time itself varies in it's rate of passage.
So yes it also seems to me that time is a sort of geometry.
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You are thinking wrongly because most people do not describe this process fully and correctly Clocks where you are always run normally and time seems to flow perfectly normally whatever speed you and the clock together are moving at however if you and the clock are moving very fast relative to someone else the person who is watching you and the clock zip by at high speed sees your clock moving slower than you would.
The correct statement is that moving clocks run slow when observed from a distance by someone who is not moving, but they continue to work normally for someone who is moving with the clock.
So are you saying that if I take two identical clocks with exact same time, keep a clock on a table in my house and take the other and go around the earth on a plane, come back and check with the clock on table, both show exact same time?
I have read that some experiment showed that the clock on a plane was actually some nanoseconds slower.
What I understand from your post is, my brother standing outside house sees the clock with me running slower but it actually is not slower. How can you get different times then?
And if I consider myself in plane to be stationary and the earth, house are moving, the clock on the table should run slower. How does that not happen? Is it because we are on Earth? would it be different if we were in space with negligible gravity? Or is that experiment itself was bogus?
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Here is the link to the experiment which showed the clock actually had slowed down.
http://www3.open.ac.uk/media/fullstory.aspx?id=19636
And the famous Hafele–Keating experiment
http://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment
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Time dilation is a well-established phenomenon - it's demonstrated every day in particle accelerators like the LHC, and by the GPS satellites.
Clocks only run at a steady rate when they are in an inertial frame of reference. (We sometimes pretend that the Earth's surface is an inertial frame of reference - it's close enough for most purposes.)
However, when you put a clock on the plane, which accelerates to cruising altitude, you are in an accelerated frame of reference (which has different rules), and when you bend the path around in a circle to bring it back to the starting point, that also requires an accelerated frame of reference. When you climb to cruising altitude, you are further outside Earth's gravitational well, so this has different rules too.
The point is that every clock in the same inertial frame of reference all slow down by exactly the same amount, so you can't tell that there is an "error" in their time-keeping specifications.
Relativity also says that objects traveling in another inertial frame of reference are also shortened in their (relative) direction of travel - but so is every ruler in that frame of reference, so you can't tell that there is an "error" in their mechanical specifications.
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do the mechanism of the clock actually slow down?
Yes!
If the clock slows down then don't the specification of the components have to be changed.
Yes!
What happens is that the electric field of a charged particle changes when it's moving; a spherical electric field goes elliptical- it flattens in the direction it's moving in (due to electromagnetism; you find that's what happens if you solve Maxwell's equations) and the field strength is lower too.
Because clocks are made up of atoms, which in turn are made up of charged particles which are held together with electric fields, this change in the field shape means that the clock shrinks in the direction of travel, and also atoms move about more slowly because the forces due to the fields are lower, and so the clock slows down.
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do the mechanism of the clock actually slow down?
Yes!
Strictly speaking, they don't "slow down" at all. "Slow" implies a change in speed, but there is no speed change because speed is a function of time. Assuming the clocks are good timekeepers they are both correct, even though they may differ. Time is purely local and it controls all processes.
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One of the complications of measuring how fast time travels in another frame of reference is the problem of comparing clocks that are moving relative to one another and/or distant from each other.
If I remember my physics correctly, it is easiest to compare two clocks if they are in the same location, moving at the same velocity.
It is harder (but possible) to compare two clocks that are:
- distant but moving together in the same inertial frame of reference
- moving in different inertial frames of reference, but co-located momentarily as they pass each other
According to Relativity, it is not possible to unambiguously compare two clocks which are moving in different inertial frames of reference, and distant from each other (or in non-inertial frames of reference).
The example given by lunar11 requires that you compare the time on two clocks at least twice. At least one of these clock readings must occur when the "moving " clock is distant from the "reference" clock, which makes it an invalid comparison.
It doesn't mean that the result is incomprehensible - you just need to examine the situation as if you were in the "other" frame of reference, where everything looks "normal" (and from their point of view, you look weird - a bit like traveling in an unfamiliar country, really).
There is a bit more here:
http://en.wikipedia.org/wiki/Relativity_of_simultaneity#Einstein.27s_train_thought_experiment
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What happens is that the electric field of a charged particle changes when it's moving; a spherical electric field goes elliptical- it flattens in the direction it's moving in (due to electromagnetism; you find that's what happens if you solve Maxwell's equations) and the field strength is lower too.
Because clocks are made up of atoms, which in turn are made up of charged particles which are held together with electric fields, this change in the field shape means that the clock shrinks in the direction of travel, and also atoms move about more slowly because the forces due to the fields are lower, and so the clock slows down.
But Wolfe - time dilation is more than an artifact of length contraction or maybe you are not saying that it is. We can get evidence for time dilation in radioactive decay and most importantly muon decay which is mediated (solely I think) by the weak interaction.
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What happens is that the electric field of a charged particle changes when it's moving; a spherical electric field goes elliptical- it flattens in the direction it's moving in (due to electromagnetism; you find that's what happens if you solve Maxwell's equations) and the field strength is lower too.
Because clocks are made up of atoms, which in turn are made up of charged particles which are held together with electric fields, this change in the field shape means that the clock shrinks in the direction of travel, and also atoms move about more slowly because the forces due to the fields are lower, and so the clock slows down.
But Wolfe - time dilation is more than an artifact of length contraction or maybe you are not saying that it is.
I'm not saying it is, but it's the same, but it comes out of the same set of equations that produce length contraction, and lack of simultaneity.
We can get evidence for time dilation in radioactive decay and most importantly muon decay which is mediated (solely I think) by the weak interaction.
Sure, but weak and electromagnetism are intimately related; they're part of the electroweak theory, which has recently been bolstered by the Higgs boson work.
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Id say moving clocks do move slower aslong as your observing them moving and not moving with them.
The distance the stationary observer sees the moving clock go through is further than the moving clock observes and so to make up for this time must slow down for the moving clock as percieved by the stationary observer.
A minute is a minute no matter who observes it the difference in observations of others keeping of time is not time.
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I have moved David's sidebranch dealing with Einstein's assertion which is demonstrably wrong to it's own thread in New Theories.
please can we keep this thread and others on the main boards restricted to mainstream ideas?
many thanks
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What happens is that the electric field of a charged particle changes when it's moving; a spherical electric field goes elliptical- it flattens in the direction it's moving in (due to electromagnetism; you find that's what happens if you solve Maxwell's equations) and the field strength is lower too.
Because clocks are made up of atoms, which in turn are made up of charged particles which are held together with electric fields, this change in the field shape means that the clock shrinks in the direction of travel, and also atoms move about more slowly because the forces due to the fields are lower, and so the clock slows down.
But Wolfe - time dilation is more than an artifact of length contraction or maybe you are not saying that it is.
I'm not saying it is, but it's the same, but it comes out of the same set of equations that produce length contraction, and lack of simultaneity.
We can get evidence for time dilation in radioactive decay and most importantly muon decay which is mediated (solely I think) by the weak interaction.
Sure, but weak and electromagnetism are intimately related; they're part of the electroweak theory, which has recently been bolstered by the Higgs boson work.
Hmm - not sure I agree there, the fact that the equation arise together does not mean that they are interchangeable, or that one encompasses the other. Time dilation is a real effect - and is not caused, nor mediated by length contraction; they both exist. Whilst there is no method I can envisage that could separate them that does not mean that one is subsumed by the other.
And weak and em are unified by the electroweak - but at 10^14K; if they were unified for atmospheric particles we would have noticed earlier :-)
Aren't muons considered point particles anyway - how can you length contract a point particle?
Muons are time dilated - and I cannot see how that can dilation could be shown to be merely a function of a length contraction, and especially not merely as an electromagnetic effect.
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Hmm - not sure I agree there, the fact that the equation arise together does not mean that they are interchangeable, or that one encompasses the other. Time dilation is a real effect - and is not caused, nor mediated by length contraction; they both exist. Whilst there is no method I can envisage that could separate them that does not mean that one is subsumed by the other.
For the second time, I never said they were the same thing. I said that the equations of electromagnetism give rise to time dilation, lorentz contraction and lack of simultaneity in material held together by charged particles (things like clocks).
These are 3 separate effects that, together, give relativity.
And weak and em are unified by the electroweak - but at 10^14K; if they were unified for atmospheric particles we would have noticed earlier :-)
Aren't muons considered point particles anyway - how can you length contract a point particle?
Muons are time dilated - and I cannot see how that can dilation could be shown to be merely a function of a length contraction, and especially not merely as an electromagnetic effect.
You do sound very, very confused. I never said that either. You would have to look at the equations of the electroweak force no doubt they have the same relativistic invariants that standard electromagnetism shows.
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According to Relativity, it is not possible to unambiguously compare two clocks which are moving in different inertial frames of reference, and distant from each other (or in non-inertial frames of reference).
Depending on what you mean by that, it's probably not true. You can place a second clock or measuring device (or camera) at any particular point in space, arbitrarily close to where a moving clock is going to be and record the time on the moving clock as it goes past.
Relativity doesn't work by smoke and mirrors; if a clock appears to be running slow (after you've allowed for light speed and other optical issues if you're viewing it from a distance) then it IS actually running slow.
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if a clock appears to be running slow (after you've allowed for light speed and other optical issues if you're viewing it from a distance) then it IS actually running slow.
You keep using the phrase "running slow". It may be more a point of semantics, but unless the clock is defective, it is not running slow. All you can say is that it was subjected to different time from another clock.
"Slow" suggests one clock was correct while the other was not, but, in fact, both clocks are correct.
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Hmm - not sure I agree there, the fact that the equation arise together does not mean that they are interchangeable, or that one encompasses the other. Time dilation is a real effect - and is not caused, nor mediated by length contraction; they both exist. Whilst there is no method I can envisage that could separate them that does not mean that one is subsumed by the other.
For the second time, I never said they were the same thing. I said that the equations of electromagnetism give rise to time dilation, lorentz contraction and lack of simultaneity in material held together by charged particles (things like clocks).
These are 3 separate effects that, together, give relativity.
Relativity flows from the constancy of physical laws in all inertial frames - the speed of light being the most important of those; this of course agrees with the prediction of the maxwell equations of the speed of electromagnetic radiation. but this is not a purely electromagnetic effect.
And weak and em are unified by the electroweak - but at 10^14K; if they were unified for atmospheric particles we would have noticed earlier :-)
Aren't muons considered point particles anyway - how can you length contract a point particle?
Muons are time dilated - and I cannot see how that can dilation could be shown to be merely a function of a length contraction, and especially not merely as an electromagnetic effect.
You do sound very, very confused. I never said that either. You would have to look at the equations of the electroweak force no doubt they have the same relativistic invariants that standard electromagnetism shows.
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lets not have jibes about confusion. Exactly which electroweak equations deal with muons in the atmosphere? ie what did you mean by this "Sure, but weak and electromagnetism are intimately related; they're part of the electroweak theory, which has recently been bolstered by the Higgs boson work." in relation to the decay of muons. The electroweak theory governs at very high energies; the electromagnetic and the weak are separate forces at the energies we are talking about. So help me in my confusion - what does the electroweak have to do with it?
Muon decay, which is governed by the weak, shows time dilation - how do maxwell's equations work in this area?
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OK - All the Einstein was wrong - the aether exists - etc has been moved (again) to New Theories. Please keep it there. Thanks
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The trick is using a convenient frame as if it is a preferred frame so that time can be treated as if it's running slow in other frames
I don't think anyone is saying that time is "running slow" in other frames (if they are, I don't think they should be). If you prefer, every atom has its own "frame" and therefore, its own time. No atom is fast, and no atom is slow.
We can clump a bunch of atoms that experience similar accelerations together into a "frame", but that's a bit artificial, although it may be convenient.