1905 Special Relativity theory Time dilation

[David]

Originally posted by cucumber
the problem is, that i do not see how time can be slowed down for both at the same time (no pun intended); time dilation should only occur for the one moving at near c, but if there is no reference frame, who experiences time dilation?

do both guys see the other guy moving in slow-motion?
if they do, i need to seriously refine my concept of time...

Let me tell you a little secret. There is an error in the 1905 Special Relativity theory that Einstein corrected with the General Relativity theory. There is no time or clock paradox in General Relativity because only one clock slows down at a time. In the original 1905 theory, Einstein had both clocks slowing down at the same rate at the same time, and that turned out to be an error, which he corrected later in the GR theory.

 

[David]

Originally posted by Ambitwistor
Untrue. General relativity does not correct special relativity, it merely treats a greater variety of situations than SR can. All SR results are GR results too.

That is a common belief, but the reason for time dilation in SR is completely different from the reason in GR. The reason atomic clocks slow down in GR and in real life is because of acceleration. There is a “force” placed upon the atoms of the clocks and this causes the internal harmonic oscillation rates of their atoms to physically slow down.

The reason the clocks slow down in SR is due to Einstein’s thought-experiment use of two “light clocks” and because of the peculiar way he synchronized them and caused them to dilate. Essentially this is an illusional kinematical phenomenon caused by an error in his thought experiments.

The dilation in GR involves only the clock that experiences the acceleration, while a reference clock does not slow down (unless it’s experiencing acceleration too). In GR, the slow clock sees the fast clock as ticking fast, while the fast clock sees the slow clock as ticking slow.

But in SR, both clocks “see” each other as ticking only slow, never fast, and slow in both directions of relative travel, and slow by the same rate. In SR theory, the clocks can either run normally or slower, but they can’t speed up. In GR theory the clocks can run slow or fast depending on the gravitational potential at or the acceleration level of the clocks.

In GR the time dilation can be caused by accelerated motion or stationary acceleration (gravity). But in SR the time dilation is causes only by “relative motion”, while acceleration is left out of the theory altogether, and no “force” of any kind is felt by the clocks.

In SR theory all clocks can “slow down” at the same rates due only to the “v” of their relative motion, but in GR theory atomic clocks slow down due to acceleration, while under the same acceleration, pendulum clocks speed up.

So SR is not a “special case” of GR. The time dilation of the kinematical part of the SR theory is completely different from the atomic clock rate slowdown of the electrodynamical part of GR theory.

 

[GijXiXj]

David

Like some of your arguments, on the other hand have to agree at least partly with ambitwistor's critique of them:

Summing over all possible values of i & j:

S² = Ó GijXiXj, i,j run 1 to 2, Pythagoras in 2-D he say! (eg: X1 = 'normal' X coordinate length, X2 = 'normal' Y coordinate length, S = hypotenuse)

S² = Ó GijXiXj, i,j run 1 to 3, Pythagoras in 3-D he say!

S² = Ó GijXiXj, i,j run 1 to 4, Gij = 0 when i not=j, else Gii = ±1 (kinda), hello to the Special Theory of Relativity.

S² = Ó GijXiXj, i,j run 1 to 4, Gij = Gji, hello to the General Theory of Relativity. (Ok, I missed out the d's).

Darn it that funny Ó symbol was supposed to come out as capital Greek SIGMA, meaning sum over all combinations of i & j. Nevermind.

Pythagoras he say! So there's a progression in generality from Pythagoras, (where Gij = 0 when i not = j, and Gij = 1 for i = j), to SR (4-D) with Gij's sticking to those 'Pythagoras rules', except one of the Gii's is opposite sign to all the others, to GR (also 4-D) where there is no such restriction on the Gij's, just a much looser one as far as I remember, rusty as hell, that Gij = Gji. So there are 16 Gij's, because i & j take the values 1-4 independently but only 10 of them are independent because Gij = Gji.

Ambitwistor will probably tear me into bone gaping shreds for this, but, ahem, the Gij kind of defines gravity through the warping of space time (the four dimensions, Xi to Xj, one of them's 'time', kinda). If none of the 16 (or 10, take your pick) Gij's differ from 0 or ±1, you get 'flat' space-time, or GR 'collapses' into 'SR'. Gij's differing from 0 or ±1, gives you the 'full' GR. Of course, there is no such thing as flat space-time, and so really no such thing as SR.

:-)

Useful approximation though.

;-)

But in the sense of a mathematical generalisation from ( ... Pythagoras ... ) --> SR --> GR, Ambitwistor's got a very good point.

... if Pythagoras had just stuck at it a bit harder ...

;-)

All that said, like you I've always felt a bit uncomfortable with the SR 'explanation' of the Twin Paradox, and talking about this and other Relativity things on another forum quite a while ago now, caused me to fiddle about with it a bit, to produce http://gijxixj.home.att.net/Relativity/GrSrTpSatExplns.htm . See if it helps.

( ... goes away and tries to think of rebuffs to Ambitwistor perhaps shredding offering to pieces ... ;-)

 

[chroot]

GijXiXj,

We use the lowercase g to represent the metric, and lowercase x to represent coordinates.

In special relativity,

g_{ij} \equiv g_{ji} \equiv \eta_{ij} \equiv<br /> \left(\begin{array}{cccc}<br /> -1&amp;0&amp;0&amp;0\\<br /> 0&amp;1&amp;0&amp;0\\<br /> 0&amp;0&amp;1&amp;0\\<br /> 0&amp;0&amp;0&amp;1<br /> \end{array}\right)<br />

i.e. it is not 0 in special relativity, as you indicated. It's a generalized identity matrix. Also, in both special and general relativity, the metric is symmetric.

- Warren

 

[GijXiXj]

Warren, you said:

" We use the lowercase g to represent the metric, and lowercase x to represent coordinates. "

Yes, I know, but then the subscripts look less like subscripts for us lazy sods who can't be bother latexing.

By, the way, as far as I know, latexing also isn't a verb, at least in the sense I use it.

You go on:

"In special relativity,

... some matrix ...

i.e. it is not 0 in special relativity, as you indicated."

Nope, I never did so indicate. Read what I posted again. I indicated pretty much exactly as you did in your matrix, but in "words", that's all: Pythag & SR: Gii = 1, except SR has one Gii = -1, i not= j then Gij = 0; GR: Gij = Gji.

 

[David]

Originally posted by Ambitwistor

Gravitation has no mechanical effect on clocks; it has a geometric effect on spacetime. Moreover, time dilation is not determined intrinsically by acceleration in GR.

Well, gravitation does cause an "effect" on some clocks. In this case, whether we call it a "mechanical" effect on atoms or an "electrodynamical" effect, I won't quibble about what we call it.

I want to show you something very interesting in “On the Influence of Gravitation on the Propagation of Light”, A. Einstein, 1911. In the paper, Einstein predicted that atomic clocks would slow down in stronger gravitational fields, such as in a valley on Earth or at the sun. But he did this in a very long convoluted roundabout way that is a little difficult to follow.

In the paper he said:

”It follows, then, that a ray of light emitted in S2 with a definite gravitational potential, and possessing at its emission the frequency v2, compared with a clock in S2, will, at its arrival in S1, possesses a different frequency v1, measured by an identical clock in S1.”

Then he says:

”Let v0 be the vibration-number of an elementary light-generator, measured by a delicate clock at the same place. Let us imagine them both at a place on the surface of the Sun (where our S2 is located).”

His “elementary light-generator” is basically a vibrating “atom”, which is a fundamental “atomic clock”, and the frequency of the light it emits is tied to its vibration rate.

Then he says that when we measure the frequency of the sunlight at the earth:

”Thus according to our view the spectral lines of sunlight, as compared with the corresponding spectral lines of terrestrial sources of light, must be somewhat displaced toward the red...”

What we basically have here in the “elementary light-generator” on the sun is an elementary atomic clock that is vibrating more slowly than the same kind of atom on Earth and is emitting light of a lower frequency at the sun because the atom is experiencing the force of the stronger gravitational potential at the sun. Its light frequency can be calculated by its shift when received at the earth, and the sun-atom’s vibration frequency shift can also be calculated. Both kinds of frequency shifts can be shown to be lower at the sun than their counterparts here on earth, because the Earth atoms experience less gravitational forces.

He is essentially saying that atomic clocks “tick more slowly” at the sun than at the earth, which I think he should have come right out and stated as simply as that. But he didn’t. He went into a long description about what “time” is at the sun and what “time” is at the earth, and he introduced two completely superfluous “delicate clocks” of no particular kind or description, which he designated as “U” clocks.

He already has the most basic and accurate clocks in the “elementary light-generators”, which are the atoms on the sun and the same kinds of atoms on earth, ie “atomic clocks”, so the introduction of the “U” clocks is not at all necessary, since they are totally imaginary and their rates are different at the sun and at the Earth in exactly the same amount as the “vibration-number of an elementary light-generator” is different at the sun and at the earth.

But he goes on to say:

“What v2 denotes is the number of periods with reference to the time-unit of the clock U in S2, while v1 denotes the number of periods per second with reference to the identical clock in S1. Nothing compels us to assume that the clocks U in different gravitational potentials must be regarded as going at the same rate... Therefore the two clocks in S1 and S2 do not both give the ‘time’ correctly. If we measure time in S1 with the clock U, then we must measure time in S2 with a clock which goes 1 + Φ/c^2 times more slowly than the clock U when compared with U at one and the same place.”

So he’s basically saying here that the “U” sun clock (which I designate U2) ticks slower at the sun than the other “U” clock (which I designate U1) ticks at the earth. So the “U” clocks themselves are nothing other than “atomic clocks”. And he says that if we want to accurately note the U2 tick rate at the sun, and duplicate that rate in a clock here on earth, then we must adjust the rate of any other kind of Earth clock by purposely slowing it down to the U2 rate, and then we compare that slower rate to the earth’s U1 clock rate. That’s what he means by, “we must measure time in S2 with a clock which goes 1 + Φ/c^2 times more slowly than the [earth] clock U when compared with U at one and the same place [at the earth].”

But this is extremely confusing in the way he words it. What he is basically saying is that on earth, we adjust and slow down a third clock, of a different kind than “U”, to the rate of the Sun’s U2 clock, and then we compare the rate of the adjusted and purposely slowed down clock with the rate of U1.

So? What did he accomplish by introducing the “U” clocks?

Nothing at all.

We already know the rate of the Sun’s U2 clock by observing the sunlight’s spectral line shift, and this gives us the vibration rate of the sun’s atoms that emit the light. Since that vibration rate is tied directly to the rate of the U2 clock, we don’t even need the U2 clock. And since the earth’s U1 clock rate is tied directly to the vibration rates of the same kinds of atoms on earth, we don’t need the U1 clock. So there is absolutely no need for any imaginary “U” clocks, since the atoms themselves are “delicate clocks” that “tick” at different rates at the sun and on the Earth because of the gravitational potential differences in both places.

So Einstein in 1911 was saying that atomic clocks slow down under strong gravity and speed up under weak gravity, but he said it in such a confusing way, that’s why in 1911 “only 12 people in all the world” could understand what he was talking about. If he had used simpler wording instead of what he did use, then most people in all the world could have easily understood what he was talking about.

So, yes, gravitation does cause an “effect” in atomic clocks. You can call it a “mechanical” effect, or an “electrodynamical” effect, or whatever you want to call it. It is a physical effect caused by a gravitational “force” being placed on the atoms. But this is not “time dilation”, its an “atomic harmonic oscillation rate slowdown”.

Originally posted by Ambitwistor

That's overly simplistic. For instance, two clocks, neither of which is experiencing (proper) acceleration, can experience time dilation relative to each other.

Yes, true, my computer clock and my wall clock constantly disagree. In aerospace, that’s called “clock drift”, and there are several causes for it. In my post I was speaking specifically of atomic clocks and acceleration.

 

[David]

Originally posted by Ambitwistor
It's neither one. Even if electrodynamics didn't exist, gravitational time dilation still would exist. Nor is time dilation restricted to clocks that operate by mechanical means, or to vibrating atoms, or whatever. Time dilation has nothing to do with how the clocks are physically constructed.

I don’t think you can say that unless you can show some observational or experiment evidence of what you say. Electrodynamics does exist and that’s why atomic clocks slow down in a greater gravitational potential.

Although it is commonly called “time dilation,” it’s actually a “clock rate change” (a slowdown or speedup) caused by some sort of force placed on or removed from the fundamental mechanism of the clock, or a changing force being felt by the clock mechanism.

Do you know of any kind of clock that doesn’t measure time by means of some kind of physical vibration or motion taking place inside or at the clock or a motion of the clock relative to something else?

I understand that a high gravitational potential speeds up pendulum clocks while it slows down atomic clocks at the same location, so here we have two different kinds of clocks changing rates in opposite directions at the same place, so this phenomenon is obviously a “clock rate change” phenomenon at each clock, not a “time rate change” phenomenon at the place.

 

[David]

Originally posted by Ambitwistor
Gravitational time dilation affects all clocks equally, no matter what their construction. The problem with a pendulum clock, however, is that it is designed to only work in one gravitational field. Even in Newtonian gravity, a pendulum clock will tick at different rates at different gravitational potentials;

So will atomic clocks.

I don’t see how you can say these things. A pendulum clock clearly speeds up where an atomic clock slows down.

Where do you get your ideas from? Why would you say that gravity slows down a pendulum clock just like it slows down an atomic clock, when 500 years of observational evidence reveals that a larger gravitational potential speeds up a pendulum clock? On what are you basing your refutations of direct observational evidence?

 

[David]

High quality pendulum clocks are adjustable for different elevations and some atomic clocks are too. The large pendulum clocks of past generations were completely adjustable for use all over the earth, at different elevations. In the 19th Century, some pendulum clocks were used to measure elevation. If you move a pendulum clock up in elevation, it will tick more slowly, and if you move an atomic clock up in elevation it will “tick” more rapidly. That appears to be a clear law of nature.

Originally posted by Ambitwistor
Einstein.

He said that atomic clocks will slow down when placed under a large gravitational potential, and observational evidence says that idea turned out to be true. But just as with the ideas of any other theorist, you need to compare everything he said to actual experiment and observation to determine what different things he said were true or untrue. In 1915 he said all stars were “fixed” and the universe was “static”. That turned out to not be true. He said in 1911 that we need the “U” clocks in his thought experiments, but that turned out not to be true.

 

[David]

Originally posted by Ambitwistor
Gravitational time dilation in general relativity has nothing intrinsically to do with atomic clocks, or the properties of atoms. (For that matter, what we call "atomic clocks" today weren't even invented in 1911.)

Maxwell talked about vibrating atoms being used as clocks as early as the 1870s. Vibrating atoms are "atomic clocks". They don't have to be enclosed in a manufactured case that is labeled "Atomic Clock" before they can be "atomic clocks".

You are talking about ancient theories as opposed to observation data, and some of those theories are now obsolete.

 

[Janus]

Originally posted by David
If you move a pendulum clock up in elevation, it will tick more slowly, and if you move an atomic clock up in elevation it will “tick” more rapidly. That appears to be a clear law of nature.

Pendulum clocks depend on gravity to work, thus the local gravitational strength will affect their operation. If you move both an atomic clock and pendulum clock up in elevation, yes the atomic clock will tick more rapidly, and the pendulum clock more slowly. BUT, If you measure the pendulum clock tick rate very carefully, you will note that it doesn't tick quite as slowly as you would expect(as compared to a pendulum clock at a lower elevation), and that difference will be exactly equal to the amount that the atomic clock ran fast (again, as compared to a clock at a lower elevation).

The pendulum clock is effected by both the lessening of local gravitational strength and gravitational time dilation, it is just that the first has the greatest effect.

The atomic clock however is not sensitive to local gravitational stength but does note time dilation due to relative difference in gravitational potential (Not the same thing as local gravitational strength).

The other difference is that a person standing next to the clocks would notice that the pendulum clock was running slow, but would see the atomic clock as running at proper speed, and would not be be aware of any speeding up of the clock. (He would note, however, that the atomic clock at the lower elevation was running slow)

 

[David]

Originally posted by Ambitwistor
I'm talking about general relativity and the gravitational time dilation which is predicted by that theory, as well as the experimental evidence for that time dilation.

Yes, but I’m talking about reality.

The reason I got into this is because all my life I worked with variable time-flow rates of different kinds, and all kinds of Doppler effects, and when I retied I wanted to read some physics books and find out what “time” is.

I was shocked to learn that most physicists don’t know what “time” is, and they have made up some of the wildest and most outrageous claims and superstitions about it. I’ve read things such as Stephen Hawking claiming that a person will “live longer” on top of a mountain because Einstein said so, and stuff like you’ve just said about pendulum clocks “time dilating” at the same rates as atomic clocks in high gravitational potentials, even though they clearly “speed up”, and stuff about relative motion causing clocks millions of miles away to “slow down”. “Relative motion” alone can’t possibly cause any clock to slow down or speed up.

These old and incorrect “time” theories have become urban legends. I’ve worked with and interviewed scientists in different fields who don’t pay any attention to them. In fact, many scientists use the observed rules of “thermodynamic time”. In fact, doctors, medical researchers, and biologists don’t pay any attention to the Einstein time superstitions. They mainly use the rules and laws of thermodynamic time.

 

[master_coda]

Originally posted by David
In fact, doctors, medical researchers, and biologists don’t pay any attention to the Einstein time superstitions. They mainly use the rules and laws of thermodynamic time.

Doctors, medical researchers, and biologists are unlikely to ever work in a situation where the affects of time dilation are significant. So why would they use a more complicated theory when the additional accuracy it provides isn't necessary? In fact, it's unlikely that most of them will even learn about relativity at all.

 

[David]

Originally posted by Janus
Pendulum clocks depend on gravity to work, thus the local gravitational strength will affect their operation. If you move both an atomic clock and pendulum clock up in elevation, yes the atomic clock will tick more rapidly, and the pendulum clock more slowly. BUT, If you measure the pendulum clock tick rate very carefully, you will note that it doesn't tick quite as slowly as you would expect(as compared to a pendulum clock at a lower elevation), and that difference will be exactly equal to the amount that the atomic clock ran fast (again, as compared to a clock at a lower elevation).

Can you post some links to some precise experiments that prove this conclusively?

 

[David]

Originally posted by master_coda
Doctors, medical researchers, and biologists are unlikely to ever work in a situation where the affects of time dilation are significant. So why would they use a more complicated theory when the additional accuracy it provides isn't necessary? In fact, it's unlikely that most of them will even learn about relativity at all.

Biologists have frozen twin embryos and thawed one out 7 years after he was conceived. The baby was 8 earth-years old when he was born. This was true “time dilation” using thermodynamic means to suspend his growth rate to “0” seconds per second for 7 atomic clock years.

All that stuff about “relative motion” time dilation is just superstition. The biologists have already done it, and they did it with thermodynamics, not “relative motion”.

 

[master_coda]

Originally posted by David
Biologists have frozen twin embryos and thawed one out 7 years after he was conceived. The baby was 8 earth-years old when he was born. This was true “time dilation” using thermodynamic means to suspend his growth rate to “0” seconds per second for 7 atomic clock years.

All that stuff about “relative motion” time dilation is just superstition. The biologists have already done it, and they did it with thermodynamics, not “relative motion”.

That is not time dilation. If someone dies at the age of 72 and then 10 years pass, did time dilate? After all, they only aged 72 years in an 82 year period.

Halting someones growth doesn't change the way time flows. It merely changes their rate of growth.

 

[David]

Originally posted by Janus
The other difference is that a person standing next to the clocks would notice that the pendulum clock was running slow, but would see the atomic clock as running at proper speed, and would not be be aware of any speeding up of the clock.

You don't know this. This is just a made up urban legend. Look, I’ve talked to the atomic clock physicists at Boulder. They’ve stood next to atomic clocks that changes rates and they know they changed rates. The rate changes are too slight to notice without the use of other reference clocks. So a person can’t possibly tell if an atomic clock changes rates unless they compare it to the read-out on reference clocks. They told me that NO manufactured atomic ever runs at the same rate. They said that two atomic clocks manufactured side by side will run at different rates when they are turned on. So no atomic clock runs at the same rate as any other atomic clock in the same place. That’s what they told me. This is clock dilation, not time dilation. Only the old theories call it "time dilation", but I've talked to too many industrial engineers who say it is meaningless.

 

[master_coda]

What are you saying? That because clocks can change rates for reasons that have nothing to do with time dilation, changes in rates never have anything to do with time dilation?

Incidentally, industrial engineers, like biologists and doctors, are unlikely to need to compensate for the affects to time dilation.

 

[russ_watters]

Originally posted by David
Yes, but I’m talking about reality.

The reason I got into this is because all my life I worked with variable time-flow rates of different kinds, and all kinds of Doppler effects, and when I retied I wanted to read some physics books and find out what “time” is.

I was shocked to learn that most physicists don’t know what “time” is, and they have made up some of the wildest and most outrageous claims and superstitions about it. I’ve read things such as Stephen Hawking claiming that a person will “live longer” on top of a mountain because Einstein said so, and stuff like you’ve just said about pendulum clocks “time dilating” at the same rates as atomic clocks in high gravitational potentials, even though they clearly “speed up”, and stuff about relative motion causing clocks millions of miles away to “slow down”. “Relative motion” alone can’t possibly cause any clock to slow down or speed up.

These old and incorrect “time” theories have become urban legends. I’ve worked with and interviewed scientists in different fields who don’t pay any attention to them. In fact, many scientists use the observed rules of “thermodynamic time”. In fact, doctors, medical researchers, and biologists don’t pay any attention to the Einstein time superstitions. They mainly use the rules and laws of thermodynamic time.

These time theories are not old and though they sound outrageous to you, but our best evidence says they are CORRECT. People in biology related fields don't use the theories because they aren't relevant for those fields. Time dilation is only significant in human terms at VERY high speed.

The field where scientists DO use the theories naturally is PHYSICS (and the related fields). In astronomy, space travel, telecommunications, etc. these theories are ESSENTIAL to making our technology work.

The GPS system is the most cited example - its a system that is built on relativity itself. It uses the timing of signals from satellites to find positions on earth. Without a clear picture of how the speed of light varies (or in fact does NOT vary) and how the rate of the passage of time varies, it would not work. http://www.metaresearch.org/cosmology/gps-relativity.asp is a decent article about what GPS tells us about Relativity.

I realize some of these concepts don't seem to make sense at first glance, but they DO work in reality. The starting point is the constancy of the speed of light. Familiarize yourself with it as the rest comes directly from it. IE, the fact that the speed of light is constant to all observers is WHY time must be variable.

You don't know this.

You misunderstood Janus's point. Obviously any clock including an atomic clock has an internal error. These errors are IRRELEVANT to this conversation because any measurements we are talking about are much, much larger than these internal errors (otherwise the measurements would be useless).

Listen, this isn't anything to get all worked up about. Your fierce opposition to these ideas is getting in the way of your ability to understand them. Let it go for a little while and look at what we are telling you. UNDERSTAND the theories and LOOK at the evidence.

Can you post some links to some precise experiments that prove this conclusively?

I doubt it. It wouldn't be an experiment that would interest a physicist and the error in a mechanical clock is high enough you would have difficulty getting a meaningful result. Please don't take that to mean the effect does not exist. It does. It has been proven as conclusively as any theory can be.

 

[David]

Originally posted by master_coda
That is not time dilation. If someone dies at the age of 72 and then 10 years pass, did time dilate? After all, they only aged 72 years in an 82 year period.

Halting someones growth doesn't change the way time flows. It merely changes their rate of growth.

No, of course not, but they are dead and out of the loop. The “rate of their growth” is a function of their own local biological body “time”. This is real biological science, not hypothetical physics theory.

The freezing of human embryos is REAL time dilation, since the embryos don’t age while frozen. They can’t freeze an entire full-grown human yet because of many problems such as cell ruptures due to water ice formation. But they are able to dry out the embryo cells so they don’t rupture while frozen.

Generally, the other “twin” frozen embryos are destroyed after one frozen embryo is successfully implanted and born several years later, but, since they usually save 6 to 10 frozen “twins” at the same time, they could thaw out one a year for 10 years and have 10 twins of 10 different real-life ages, aged 1 to 10. I’m not sure if these are fraternal or maternal twins, but they are conceived at the same time in a lab. You can look this up on Google under “frozen embryos”.

Einstein discussed thermodynamic time dilation in his 1907 “update” of the SR theory, but he wound up with a paradox in it to, since he said that both systems “see” the other system get colder during the “relative motion”. This is the logical consequence of an illogical theory, since when someone “sees” “time slow down” in another frame, they “see” the molecular vibration rates in that other frame slow down, and that is what produces the thermodynamic effect, but in SR theory, it is just an illusion, just as the “time dilation” is an illusion. Just as the “time dilation” of Doppler theory is an illusion. But a great urban legend has grown up around the SR theory, that says the “time dilation” due to “relative motion” is “real”, but it’s not “real”.

Clock dilation in GR theory is real.

 

[master_coda]

Originally posted by David
The freezing of human embryos is REAL time dilation, since the embryos don’t age while frozen. They can’t freeze an entire full-grown human yet because of many problems such as cell ruptures due to water ice formation. But they are able to dry out the embryo cells so they don’t rupture while frozen.

And dead people don't age after they die. Being dead does not magically "remove you from the loop". Frozen or dead, time does not flow differently. You simply don't do anything.


And as for SR...so do you accept that there are experiments that show time dilation, and you are just arguing that the observed dilation is an illusion and not real?

 

[David]

Originally posted by master_coda
And dead people don't age after they die. Being dead does not magically "remove you from the loop". Frozen or dead, time does not flow differently. You simply don't do anything.

The biologists look at time differently. To them, atomic time is assumed to be extremely stable, even “absolute” as far as living organisms are concerned.

But heat (temperature), ie “thermodynamic time”, strongly affects life functions. The freezing of the embryos represents a “suspension” of the thermodynamic time-flow of the organism that is frozen.

This is true “time dilation” as far as that organism is concerned. Of course, if you are frozen and the vibration rates of your molecules are slowed down so that they “don’t do anything”, then you, in your own “system”, are infinitely “time dilated”, while the rest of time continues to flow around you. If the embryo is frozen, one second of everybody else’s time = 0 seconds of embryo time.

Your own personal “system” in biology is not an “inertial frame”, it is your body and everything inside it.

Biologists don’t think in terms of “inertial frames”, they think in terms of “body frames” or individual organism “systems”. Your body is your “frame” or “system”, and it is regulated by the biological rules of “thermodynamic time”. The physics concepts of “atomic-clock time dilation” and “relative motion” just don’t apply in biology.

 

[russ_watters]

Originally posted by David
The biologists look at time differently. To them, atomic time is assumed to be extremely stable, even “absolute” as far as living organisms are concerned.

The physics concepts of “atomic-clock time dilation” and “relative motion” just don’t apply in biology.

We told you this already. For a biologist, this topic is unimportant. For a physicist, its ESSENTIAL.

 

[David]

Originally posted by russ_watters
We told you this already. For a biologist, this topic is unimportant. For a physicist, its ESSENTIAL.

Yes, atomic clock rate changes due ro gravitational potential changes are very important, but these aren’t “time dilations”. They are clock rate changes. The clocks speed up or they show down. The clocks.

 

[russ_watters]

Originally posted by David
Yes, atomic clock rate changes due ro gravitational potential changes are very important, but these aren’t “time dilations”. They are clock rate changes. The clocks speed up or they show down. The clocks.

No. And whether you believe it or not, its the truth. The evidence is overwhelming and incontrovertible.

If you are really interested in learning about this, pick up a laymans' book about relativity. And have a look at the link on GPS I posted.

 

[Integral]

The statements of your beliefs do not constitute a proof.

You need to separate belief from knowledge. While you have very strong beliefs about these matters it is clear that you have very little knowledge. It would be to your benefit if you could suspend your disbelieve of the current state of Physics and read the responses to your ideas with an open mind. You have been presented the physics as it is now understood why not make an effort ot understand it.


Your web page is a presentation of your beliefs, I could not detect a single proof of their correctness. Until you learn that the language of Physics is mathematics, you will never be able to present your ideas in a coherent fashion. Your arguments are not convincing, without the systematic logic of a carefully Mathematical presentation you can prove nothing.

The reason Einstein's concepts became universally accepted was due to his careful and through mathematical presentation. If you are going to argue against Time dilation you will have to find errors in the math, you have not done so.

 

[David]

Originally posted by Integral
The statements of your beliefs do not constitute a proof.

You need to separate belief from knowledge...

Your web page is a presentation of your beliefs, I could not detect a single proof of their correctness.

Are you talking to me? I don’t have a “webpage”.

I don’t have a “disbelief in the current state of physics”.

Without the current state of physics, we wouldn’t have airplanes, rockets, TV, computers, Doppler radar, or Doppler sonograms.

Einstein produced many “concepts” in his lifetime. Not all were correct. His idea about a “static” universe was not correct. Many physicists now believe the universe is “expanding”. His idea that only “relative motion” causes real “time dilation” was not correct. Relative motion between objects separated by great distances can’t (in my humble opinion) possibly cause either of their atomic clocks to slow down. But a great myth has grown up about “relative motion” causing clocks to “slow down”.

Atomic clocks can apparently slow down if they are moved rapidly though fields, but if this happens, it wouldn’t be due to “relative motion”, it would most likely be due to the motion of the clocks through the fields.

There are physics websites on the internet that say outright or imply Faraday’s discovery that an electron flow caused by the movement of a magnet near a coil of wire, or the movement of the coil near a magnet is a demonstration of Einstein’s special relativity theory.

But this is clearly not the case. It’s not the “relative motion” that causes the electron flow in the wire. It’s the changing field strength of the magnet, at the coil, that causes the electron flow. We don’t even need “relative motion” for this to happen if we use an electromagnet and vary its voltage.

One university website says:

“In 1905, Einstein proved that electricity and magnetism were one and the same (the difference is a matter of perspective)”

http://216.239.39.104/search?q=cach...lec17.ppt+magnet+coil+einstein&hl=en&ie=UTF-8

Is this true? Are electricity and magnetism “the same thing”?

And look at this:

http://www.physics.umd.edu/lecdem/services/demos/demosp1/p1-21.htm

This experiment was originally conducted and explained by Faraday, not Einstein. This doesn’t demonstrate anything about Einstein’s “special relativity” theory. I just shows two different ways to make a coil of wire experience a changing magnetic field when the coil and the magnet are at close range. This has nothing at all to do with “relative motion”. If the coil were in Los Angeles and the magnet were in New York, no amount of “relative motion” between the two would cause electrons to flow in the coil, so it’s not “relative motion” that causes the electrons to flow in the coil.

I think it should be the responsibility of university physics departments to dispel these old myths, rather than to continue to teach them to students.

 

[Janus]

Originally posted by David


Einstein produced many “concepts” in his lifetime. Not all were correct. His idea about a “static” universe was not correct.

Einstein did not produce this concept, he merely accepted the prevaling opinion by science at the time on this issue.

There are physics websites on the internet that say outright or imply Faraday’s discovery that an electron flow caused by the movement of a magnet near a coil of wire, or the movement of the coil near a magnet is a demonstration of Einstein’s special relativity theory.

But this is clearly not the case. It’s not the “relative motion” that causes the electron flow in the wire. It’s the changing field strength of the magnet, at the coil, that causes the electron flow. We don’t even need “relative motion” for this to happen if we use an electromagnet and vary its voltage.

You are misinterpreting what these sites are saying. Maxwell's equations (concerning electromagnetic behavior) predicted that you would get one result if you the coil was moving, and a different result if the magnet was moving.

Of course this doesn't turn out to be the case. It doesn't matter whether you move the magnet or coil.

Now in SR there is no preferred state of motion; you can't say whether A or B is moving, only that A and B have a Relative motion with respect to each other.

By Applying the transformations of SR to Maxwell's equations, He showed that they made the same prediction no matter which (coil or magnet) was considered moving; IOW, it was only the Relative motion of the two that mattered.

Thus, without SR, you get different result from a coil and magnet if you move one as opposed to the other.

With SR you get the same results no matter which one you move.

Since experiment shows that it doesn't matter which one moves, This is a demonstration of the correctness of SR.

This is what that second link you gave was about.

Since I can't get the content of the first link to come up properly, I can't really comment on what it really says.

 

[David]

Originally posted by Janus
Since experiment shows that it doesn't matter which one moves, This is a demonstration of the correctness of SR.

No it’s not. The phenomenon of the electron flow occurs when an electromagnet is used, even if there is no “relative motion”. The “motion” is not what produces the electron flow, the variation in the magnetic field at the coil is what produces the electron flow.

I don’t know about any errors in Maxwell’s point of view, but I have some old physics textbooks from the 1920s and ‘30s and they say the effect is caused by the changing magnetic field strength at the coil. They don’t say anything about this having anything to do with “relative motion”. They say it has to do with the changing field strength at the coil, and they say the same thing can be accomplished by using an electromagnet and by varying the voltage to the electromagnet, with no relative motion involved. There is no need to mention SR in connection with this Faraday discovery.

But this UCLA Physics Department website tries to make it appear as an Einstein discovery and an Einstein phenomenon:

LINK TO SOURCE

And I don’t think this website is correct about the Lorentz force being involved, because it is my understanding that for a Lorentz force to be involved, a separate current has to already be flowing through the coil before the magnet is introduced.

When I go to electrical websites, I get the stuff about Faraday and about the electromagnet. But when I go to some physics websites, I don’t. I just get the stuff about Einstein and the “relative motion”, but nothing about the electromagnet.

What is the reason for bringing SR and Einstein into this stuff? Galileo wrote about relativity. Newton wrote about relativity. Doppler developed a great theory based on his understanding of relativity. Poincare wrote about the relativity of motion in 1902. Lorentz wrote the first modern relativity paper in 1904.

People knew thousands of years ago that if person 1 moved toward person 2, while person 2 stayed still, they would get closer together. While if person 1 stayed still and if person 2 moved toward person 1, they would also get closer together. So I don’t understand the significance of Einstein’s “relativity theory” in these types of relative motion demonstrations. And of course “the laws of physics are the same everywhere”. But physicists have known that for hundreds of years.

I think Einstein did great work with General Relativity, and he deserves all the credit he can get for that. In fact, let’s give him a couple of more Nobel Prizes. But some of this other stuff about “special relativity” seems to be a lot of nonsense.

I’ve had people on the internet, people who have studied university physics, telling me all sorts of incorrect things about relative motion and “time dilation”, while they don’t know the first thing about the Doppler Effects. They don’t even know there is more than one Doppler Effect. They can give me a lot of misinformation about the motion of light photons and alleged clock slow-downs, but they can’t even tell me the physical phenomena involved in why an observer on an open car at the end of a moving train hears no Doppler shift from the moving train’s moving whistle.

They don’t know it’s because the moving observer encounters the stretched out (redshifted) wavelengths at a speed of faster than the normal speed of sound, or that the “blueshift” effect caused by the observer’s motion cancels out the “redshift” effect caused by the train whistle’s motion. When I explain this to university graduates who have had several physics courses, they act like they’ve never heard this explanation before. They know nothing about it, but they seem to know all about the special relativity urban legends.

 

[Integral]

Words are cheap. Wheres the proof to anything you say.

While you respond to a portion of my previous reply you neglected the most important part. Clearly you have no appreciation for the link between math and physics.

Show us were the math is wrong.

Einstein's original paper deals with Electromagnetism. Notice that this is a MATHEMATICAL presentation. If you wish to find errors in our current understanding you need to address the math in this paper.

What you see in different web pages is common in physics there are different levels of approach. Undergrad courses in E&M do not usually give the relativistic view point. The goal is to first teach the fundamentals. An education in physics consists of about 3 times through the same material, once is lower division university courses which are taken by most College of Science and Engineering students, the second time through is in Upper division University classed, these are taken mainly by undergrads majoring in Physics. The Third time through is presented in Physics graduate level courses.

Your arguments appear to be based somewhere below the first time through, yet you have the gonads to argue with those have 2nd and 3rd time through knowledge.

Why don't you make and effort to learn?

 

[Janus]

Originally posted by David
No it’s not. The phenomenon of the electron flow occurs when an electromagnet is used, even if there is no “relative motion”.

This is not germane to the discussion at hand

The “motion” is not what produces the electron flow, the variation in the magnetic field at the coil is what produces the electron flow.

Where do you get this notion That Relativity tries to replace variation in the strength of the magentic field felt by the electron with "motion"?

None of the sites you have provided say this.

What they do say is that after the discovery of the wave nature of light and prior to SR, theory predicted that the variation that the Electron saw would differ depending upon wheter the magnet or electron was moving. SR corrected this.

I don’t know about any errors in Maxwell’s point of view, but I have some old physics textbooks from the 1920s and ‘30s and they say the effect is caused by the changing magnetic field strength at the coil. They don’t say anything about this having anything to do with “relative motion”. They say it has to do with the changing field strength at the coil, and they say the same thing can be accomplished by using an electromagnet and by varying the voltage to the electromagnet, with no relative motion involved. There is no need to mention SR in connection with this Faraday discovery.

Again, you are fixating on the wrong thing and misinterpreting SR's contribution.

But this UCLA Physics Department website tries to make it appear as an Einstein discovery and an Einstein phenomenon:

LINK TO SOURCE

No it doesn't, It merely restates what II've been saying. You are reading meanings inot the post that aren't there.

And I don’t think this website is correct about the Lorentz force being involved, because it is my understanding that for a Lorentz force to be involved, a separate current has to already be flowing through the coil before the magnet is introduced.

Considering the lack of grasp of the subject you've displayed so far, I wouldn't put much weight in your understanding.

When I go to electrical websites, I get the stuff about Faraday and about the electromagnet. But when I go to some physics websites, I don’t. I just get the stuff about Einstein and the “relative motion”, but nothing about the electromagnet.

This is because these physics sites are talking about it on a different level. Thye feel no need to discuss Faraday etc, because they expect it to be common knowledge to the reader. (You don't review the rules of addition and subtraction in a discussion of Calculus.)

What is the reason for bringing SR and Einstein into this stuff? Galileo wrote about relativity. Newton wrote about relativity. Doppler developed a great theory based on his understanding of relativity. Poincare wrote about the relativity of motion in 1902. Lorentz wrote the first modern relativity paper in 1904.

People knew thousands of years ago that if person 1 moved toward person 2, while person 2 stayed still, they would get closer together. While if person 1 stayed still and if person 2 moved toward person 1, they would also get closer together. So I don’t understand the significance of Einstein’s “relativity theory” in these types of relative motion demonstrations. And of course “the laws of physics are the same everywhere”. But physicists have known that for hundreds of years.

Einstein made no claims as to inventing the Principle of Relativity(In fact he was opposed to calling his theory "The Theory of Relativity", this name was coined by others.)

And yes, the Principle of Relativity held sway for hundreds of years. But during that perod of time light was considered particulate in nature. But once the wave nature of light was discovered, a problem occured. What did light wave through? If there was a medium (the Ether) then that medium now represented an absolute reference to judge motion by. (For instance, magnets moving with repect to the Ether behave differently than ones stationary to it. ) Thus you should be able to measure your movement through space. This appeared to be a death toll to the Principle of Realtivity.

Many people tired to resolve this conflict but only uncovered pieces of the puzzle. Einstein was the first to put the right pieces together in a way that resolved things in a complete way, and along the way resurrected the Principle of Relativity.


I think Einstein did great work with General Relativity, and he deserves all the credit he can get for that. In fact, let’s give him a couple of more Nobel Prizes. But some of this other stuff about “special relativity” seems to be a lot of nonsense.
[/B][/QUOTE]

If it seems nonsense then you just haven't invested enough time in trying to understand it. You've just labeled it "nonsense" and rejected it.

 

[David]

Originally posted by Janus
If it seems nonsense then you just haven't invested enough time in trying to understand it.

Ok, ok, maybe I’m just stupid, so maybe you can explain something to me. Could you go to that UCLA physics website here:

LINK TO SOURCE

and read that page and read about what Lucy and Ringo both see.

Notice that Ringo sees no electric field and he sees a different law of physics being responsible for causing the electron flow in the coil, a different law than the one Lucy sees, while Lucy does see an electric field.

Now, since Lucy is moving with the coil, and Ringo is moving with the magnet, what would happen if Lucy stopped moving with the coil (while some other student takes over her job of moving the coil) and then Lucy goes over by Ringo and starts moving with him toward the coil?

Does this mean that the laws of physics change for Lucy and the electric field suddenly goes “poof” and disappears for Lucy, but not for the other students in the room?

If so, how do the coil and the magnet know that Lucy has changed positions? In fact, how do the coil and the magnet know what Ringo is doing?

How does nature know that it should change the laws of physics for Lucy when she changes position and motion orientation, but not change the laws for the rest of the students in the class?

What did Faraday say about the relative motion and position of himself and his fellow lab technicians when he was conducting his coil and magnet experiments?

 

[krab]

Originally posted by David
Does this mean that the laws of physics change for Lucy and the electric field suddenly goes “poof” and disappears for Lucy, but not for the other students in the room?

This is precisely the point. We believe the laws of physics do NOT change. That's called the principal of relativity. It was believed by Galileo as well. In 400 years, it has never let us down.

Since the laws of physics do not change, the observed effects (magnetic, electric fields and forces) MUST be due to one and the same law of physics.

 

[David]

Originally posted by krab
This is precisely the point. We believe the laws of physics do NOT change. That's called the principal of relativity. It was believed by Galileo as well. In 400 years, it has never let us down.

Since the laws of physics do not change, the observed effects (magnetic, electric fields and forces) MUST be due to one and the same law of physics.

Well, that’s just common sense in a modern world without primitive superstitions, but that UCLA Physics Department webpages says the laws of physics do change and are different for different observers. That’s why Lucy sees a field while Ringo does not. That’s why Lucy stops seeing the field if she joins Ringo, while the rest of the class sees the field. This is just plain nuts.

That’s why I’m asking people here about that webpage.

The UCLA webpage says their theory comes directly from Einstein’s Special Relativity theory, and in the first paragraph of his 1905 paper, he does mention the very same phenomena of one viewer seeing an electric field and another viewer not seeing a field at the same time, in the same room. This is not science, it’s superstition. And I’m asking, “Why is a major university teaching this kind of science superstition?“

 

[krab]

Originally posted by David
...but that UCLA Physics Department webpages says the laws of physics do change and are different for different observers. ... This is just plain nuts.

...“Why is a major university teaching this kind of science superstition?“

I read the web page and I really do not know what your problem is with it. Here is their conclusion:

The Conclusion: Electric and magnetic fields are not invariant entities themselves, but are aspects of a single entity, the electromagnetic field, which manifests itself differently to different moving observers.

In my previous post, I said basically the same thing, and you said that's just plain common sense. So what actually is your problem??

 

[David]

Originally posted by krab
In my previous post, I said basically the same thing, and you said that's just plain common sense. So what actually is your problem??

You did not say “basically the same thing”, and I think you are missing the point of what the UCLA website is trying to tell students. It’s not saying that students will see different phenomena from different points of view if they are moving. What the UCLA website is saying is not like saying one student will see one group of reflections in a mirror while another student in a different part of the room will see a different group of reflections, while the laws of physics are the same for all the mirror reflections. The UCLA website is saying that the laws of physics regarding mirror reflections are different for different students, because of their different positions and different motion orientations.

The laws of physics at a magnet and coil do not change, due only to an observer’s “relative motion” as an outside observer. By “outside” I mean, as long as the motion of the students does not in any way physically affect what is going on at the magnet and coil. If a student comes into the room with a larger magnet, and moves around with it, then that could affect what is going on at the original magnet and coil, but that has nothing at all to do with the student as an observer. It has only to do with the new magnetic field strength at the original magnet and coil.

The “electric field” inside that classroom does not disappear from the classroom for some students but not for others. To claim such a thing is only superstition and magic.

If a student sees a polarized-light reflection inside the classroom, and another student doesn’t see it because he’s wearing polarized glasses, that does not mean that the reflection “exists” inside the classroom for one student, while it “does not exist” in that classroom for another student or that the laws of reflection have “changed”. The reflection “exists” for both students, although one might see it and the other might not.

If there is an electric field at the magnet and coil in that classroom for some students, then there will be an electric field at the magnet and coil for all students and for all people on earth. The viewing and the motion orientation of the viewer has nothing at all to do with the law of physics that causes the electron flow inside the coil when the coil and the magnet are moving relatively. This law does not change just because someone in the classroom is walking around or not walking around.

 

[David]

Originally posted by krab
So what actually is your problem??

You don’t have any problem with the UCLA physics website saying:

With the coil moving:

“In case A there is only a magnetic field in the classroom"

With the magnet moving:

" but in case B there is also an electric field in the classroom. It is this electric field that is acting on the elections to cause the galvanometer deflection in case B.”

??

You don’t have a problem with the UCLA physics department saying there are two different laws of physics at work, one for Lucy and a different one for Ringo, although Lucy and Ringo have absolutely nothing whatsoever to do with the reason the electrons flow through the coil? You don’t have a problem with two separate and different laws of physics being at work on the magnet and coil for different groups of students inside the classroom, not two laws simultaneously, but two different laws that apply to certain students when they are moving in certain ways inside the classroom, or, for that matter, a thousand miles away from the classroom?

 

[ahrkron]

Originally posted by David
You don’t have any problem with the UCLA physics website saying:

With the coil moving:

“In case A there is only a magnetic field in the classroom"

With the magnet moving:

" but in case B there is also an electric field in the classroom. It is this electric field that is acting on the elections to cause the galvanometer deflection in case B.”

The problem you point at is precisely what motivated Einstein to develop SR. The site uses this problem so similarly motivate students to think about electrodynamics as seen from different inertial frames.

As you mention, there cannot be two different laws in action, which means that electric and magnetic fields must be two aspects of the same thing.

In SR, both fields are put together into the so called "electromagnetic tensor", a 4x4 matrix that allows you to extract the electric and magnetic components of the field for any frame you want. Once we do that, there are no "two laws" anymore, and we get a better understanding of the relation between the "two" fields (electric and magnetic).

 

[David]

Originally posted by ahrkron
The problem you point at is precisely what motivated Einstein to develop SR. The site uses this problem so similarly motivate students to think about electrodynamics as seen from different inertial frames.

As you mention, there cannot be two different laws in action, which means that electric and magnetic fields must be two aspects of the same thing.

In SR, both fields are put together into the so called "electromagnetic tensor", a 4x4 matrix that allows you to extract the electric and magnetic components of the field for any frame you want. Once we do that, there are no "two laws" anymore, and we get a better understanding of the relation between the "two" fields (electric and magnetic).

Einstein pretty much says that toward the end of Section 6 of his 1905 paper. Apparently, what he said in the opening paragraph was a legend left over from the 19th Century, and he tried to straighten it out in the Electrodynamical part of his theory.

But, that UCLA website tries to give the impression that the “electric field” is not in the classroom, when some students – just one student – moves a certain way, and that is wrong. That is “magic”, not science.

Read that website again, the professor who wrote the paper says there is no electric field when a student moves a certain way. The writer said, “In case A there is only a magnetic field in the classroom, but in case B there is also an electric field in the classroom.” But this is not true. The electric field can’t be made to appear and disappear just by the movement of the students.

This is a common myth that came out of Einstein’s error in the Kinematical part of the 1905 paper, in which he said that only “relative motion” could cause mechanical clocks to change rates. That can’t happen, because “relative motion” puts no “force” of any kind on the clocks.

He cleared up this error in 1918 when he added a gravitational field to the K’ frame, and that caused the frame’s atomic clocks to slow down.

His atomic clock slow-down theory came out of his 1911 gravitational redshift theory, and that turned out to be correct, because it is based on real physics electrodynamical effects that take place inside the atoms, but his mechanical clock “slow-down” due only to “relative motion”, in the 1905 paper, turned out to be a mistake, and he corrected that mistake later. But this UCLA professor is passing along that same mistake, by claiming that the relative motion of a single student can remove the electric field from the area of the coil and magnet, and that is not true. This is not the proper way to teach “relativity”, and it should not be taught incorrectly.

 

[ahrkron]

Originally posted by David
But, that UCLA website tries to give the impression that the “electric field” is not in the classroom, when some students – just one student – moves a certain way, and that is wrong. That is “magic”, not science.

Depending on how you move with respect to the field, you will observe a different decomposition of it into electric and magnetic fields. The physics is the same, what changes is the names we give to each part of the field. No magic here.

Before SR, people thought they were two different fields, and it was indeed peculiar that they transformed in such a way as to keep the observed effects the same.

However, Einstein cleared things up (starting not from electrodynamics, but from the much more basic notion of simultaneity), and showed how the same physical magnitude is seen differently by different observers.

In a (special-)relativistic formulation of electromagnetism, we don't talk about each field, but use instead the field strenght tensor

F^{\alpha\beta} = \partial^\alpha A^\beta - \partial^\beta A^\alpha

(where A is the four vector formed from the electric and magnetic potentials)

This contains both the electric and magnetic components. It allows you to easily transform from one reference frame to another, and to read the values of each field you will measure in the new frame.

Also, once written this way, Maxwell equations reduce to two nice tensorial equations which work in every inertial frame. No need for magic or for special treatment to any observer.

Read that website again, the professor who wrote the paper says there is no electric field when a student moves a certain way.

What happens is that, if that student uses some instruments, he will detect only a magnetic field. This is not magic, but a result of the way we defined electric and magnetic fields. In a sense, we can say that the limited understanding of the full picture led people to define detector devices that detect only a motion-dependent portion of the full electromagnetic tensor.

The electric field can’t be made to appear and disappear just by the movement of the students.

You do get different readings of the electric and magnetic fields depending on how you move. See, for instance, J.D. Jackson's "Classical Electrodynamics", 2nd ed., section 11.10 (page 552), or any book on electrodynamics.

There are invariant quantities related to the field-strength tensor that are frame-independent, but the electric and magnetic "views" will change.

They are akin to relative speed. If you move, the speed you measure from electrons around you will be different. Similarly, the electric field you'll read from your interaction with them will vary.

[Einstein] said that only “relative motion” could cause mechanical clocks to change rates. That can’t happen, because “relative motion” puts no “force” of any kind on the clocks.

Why should force be involved? time dilation is not an alteration of the behavior of your observed system, but a real effect on the quantities you will measure from it.

A simple example: in particle accelerators, the particles that come out of a proton-antiproton collision will have different speeds. If you want to measure the lifetime of a particular species of particle, you need to factor in time dilation. Otherwise, you would obtain results all over the place.

Gravity has nothing to do with it. In particle accelerators, all interactions take place at essentially the same gravitational potential, and you do see the effect of time dilation.

He cleared up this error in 1918 when he added a gravitational field to the K’ frame, and that caused the frame’s atomic clocks to slow down.

This is a different effect, which adds on to the SR part when you have a curved spacetime (i.e., a significant gravitational field).

His atomic clock slow-down theory came out of his 1911 gravitational redshift theory, and that turned out to be correct

You should say "it also turned out to be correct". Time dilation has been verified in many contexts. It is a real effect.

 

[Tarupak]

If math is the way to understand physics, why is it applied in a different way in SR?

in mechanics, it is taught
x = x0 + vt

dx/dt = v

x0 is constant and dxo/dt = 0

and in SR

x' = gamma(x - Vt)

So, why x in SR is changing?. This is an asumption that leads to Vx = V (the changing rate in x is equal to the separation speed of the 2 frames) What's the real reason for that equalty?

If we assume that x is constant we must derive it as a constant.

Or if Vx = V and we integrate the speed equation we must integrate V because it is equal to Vx.

 

[THE[>U<]DUDE]

Well I've just been reading Greene's Elegant Universe and am having a hard time getting my head around this time dilation between George and Gracie. It just doesn't seem to make sense to (uneducated) me.

Surely an observer's independent observations of clocks traveling at near to light speed are affected by the time delay of the light traveling to the observer to provide him with that information?

If the clock is traveling away from the observer at near light speed, then it's going to take longer for the light to reach the observer (because of the increasing distance traveled by the clock) and so the clock's apparent time will appear to have slowed down.

To me this doesn't prove time dilation exists. It just shows that at near light speed it will take longer for the 'back-travelling' light to reach the observer - and so the time readings will differ.

Does this make any sense?

 

[ahrkron]

Originally posted by THE[>U<]DUDE
To me this doesn't prove time dilation exists. It just shows that at near light speed it will take longer for the 'back-travelling' light to reach the observer - and so the time readings will differ.

Does this make any sense?

It does. It is a common problem when people learn SR.

The main point to make is that, even after accounting for the time it took light to reach George, there's still a difference between his time and Gracie's.

 

[russ_watters]

Originally posted by THE[>U<]DUDE
Well I've just been reading Greene's Elegant Universe and am having a hard time getting my head around this time dilation between George and Gracie. It just doesn't seem to make sense to (uneducated) me.

I've actually found that the problem isn't generally one of understanding but one of acceptance. Don't sell yourself short - you seem to understand it but are looking for ways it could be wrong because its difficult to accept. Everyone does it and its proof that you're thinking.

Surely an observer's independent observations of clocks traveling at near to light speed are affected by the time delay of the light traveling to the observer to provide him with that information?

If the clock is traveling away from the observer at near light speed, then it's going to take longer for the light to reach the observer (because of the increasing distance traveled by the clock) and so the clock's apparent time will appear to have slowed down.

This issue is why I consider GPS satellites to be the simplest (and therefore best) examples of time dilation. The satellites travel in fixed orbits so issues with their motion are easier to filter out than if you are just trying to communicate with a spaceship moving directly away from you.

If the satellite flies over the same spot every 90 minutes (slight oversimplification), then all you have to do is compare the time passage of the clock on the ground to the clock on the satellite. The clock on the ground says the satellite passed overhead 90 minutes ago. The satellite reports it passed over slightly more than 90 minutes ago (because of the combined SR & GR effects).

In actuality, gps satellite clocks are calibrated BEFORE LAUNCH to run slower than their terrestrial counterparts so when in orbit they will remain in sync.

 

[THE[>U<]DUDE]

Thanks for your replies; I'll try and figure it out!

On a similar vein, I wonder if you could clarify a few points...

Do clocks (or whatever we choose to measure time with) slow down increasingly with greater acceleration?

If so, is this only in areas of curved space or do the same rules apply out in the flat regions of interstellar emptiness (i.e. where mass hasn't warped space)?

Do we humans age at a slower rate in a gravity well than in regions of non-warped space?

If so, if we could 'un-warp' space around us (so that we were cocooned in a bubble of flat space) would we observe our Earthly surroundings moving in slow-motion?

Thanks for bearing with me.

 

[russ_watters]

Originally posted by THE[>U<]DUDE
Do clocks (or whatever we choose to measure time with) slow down increasingly with greater acceleration?

No- with greater speed.

Do we humans age at a slower rate in a gravity well than in regions of non-warped space?

Simple answer: yes. Complicated answer: no, we age at the same rate, but TIME ITSELF advances slower, causing us to APPEAR to age slower to an observer in a lower gravitational potential.

If so, if we could 'un-warp' space around us (so that we were cocooned in a bubble of flat space) would we observe our Earthly surroundings moving in slow-motion?

Sure, but before we can create a negative gravitational field (if such a thing even exists), we need to figure out how to create a positive one. An easier way would be to just fly to a place of low gravitational potential. A Legrange point for example.