RELATIVITY - Joke or Swindle?

[recall15]

quoted from:
http://www.cfpf.org.uk/articles/scientists/essen/essen.html

"Einstein's use of a thought experiment, together with his ignorance of experimental techniques, gave a result which fooled himself and generations of scientists. He convinced himself that the theory yielded the result he wanted, because the contraction of time is accompanied by the contraction of length needed to explain the Michelson-Morley result.

The round trip could not have been made without acceleration being applied, but Einstein ignored their possible effect on the rate of the clock, thus implicitly assuming that they had no effect. Some years later, in 1918, he used another thought experiment in an attempt to answer criticisms of the paradox result. One of the clocks again made a round trip, the changes of direction being achieved by switching gravitational fields on and off at various stages of the journey, the time recorded by the moving clock was less than that recorded by the stationary clock. The result did not follow from the experiment, but was simply an assumption slipped in implicitly during the complicated procedure. The slowing down of clocks which he had previously attributed to uniform velocity, acceleration having no effect, he now attributed to acceleration, a line of argument followed in many textbooks."

Well, back to the school again....and again and again...

Comments are welcome... /ttiforum/images/graemlins/confused.gif

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Is Titorian45 here as Agent Smith on the Matrix?

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[Titorian45]

Yes, I am still here.

 

[Sigo2507]

The bottom line is, that relativity works. It gives correct predictions to a variety of experiments. So even IF the criticism presented on that site was valid (and it is not), relativity would still be far from being a "joke" or a "swindle".

Relativity has been confirmed by countless experiments, from atomic clocks carried on airplanes and the space shuttle, to the longevity of short-lived particles going near light speed.

By the way, according to relativity, acceleration does not affect time. The two factors which affect it are speed and gravity. What Einstein's general relativity from 1915 (not 1918) tells us, is that acceleration in one reference frame can be viewed as a gravitational force in another.

For example, in the twin "paradox", when the ship deccelerates and turns around, the astronauts feel a force pushing them away from their chairs. From their point of view, there is a real force acting upon them, which can be interperted as gravity - thus slowing down their own clocks. But from the earth's point of view, this "force" is nothing more than the effect of inertia on bodies in an accelerating vehicle, and it therefore has no effect on the time dilation calculations.

Of-course, in both reference frames, you will have to add the usual effect of speed, which slows down moving clocks.

To summarize:

The earth will see the astronauts' clock slowed down, simply because they are moving at high speed (the fact that it is accelerated motion has no relevance to the calculation).

The astronauts will see the earths' clocks slow down due to the relative motion. BUT they will also see their own clocks slow down because of the force they are feeling when the ship slows down. And it can be mathematically proven, that when you add these two effects together, they would result in the earth's clocks being fast - by exactly the same amount the ship's clocks seem slowed down to those left on earth.

Of-course, the first calculation is much simpler than the second. And since there is a mathematical proof that both calculations always give the same result, nobody uses the second method for calculating the effects of twin paradox.

 

[Sigo2507]

By the way, Essen's claim regarding the accuracy of atomic clocks is wrong.

I've found some details regarding the results of the experiments, here:
http://en.wikipedia.org/wiki/Hafele-Keating_experiment

Note the uncertainties, which are all 23 nanoseconds or less. Far below the 300 nanoseconds claimed by Essen. You would have expected, that since Essen is an expert on atomic clocks, he would not make such a blunder. Makes you wonder, whether he isn't deliberately misleading his readers with this false information.

And at any rate, today there's no need for such high precision clocks, anyway. GPS satellites, due to their high altitide, gain 38 microseconds every day. The design of the GPS navigation system must take this fact into account. Every time you use a GPS device, you are relying on the designer's assumption that relativistic time dilation is real.