Relativity in brief... or in detail..
Beyond Relativity 3: So, you know where Einstein went wrong.You've found an error in the theory of relativity? Please join the queue. We often receive emails and letters showing us "errors" in relativity. So far, all of these have evaporated upon inspection. In nearly all cases, it appears that the authors have spent no more than hours or weeks reading and attempting to understand the theory that they propose to disprove. And so the issue is usually resolved by showing their misunderstanding of relativity.
So please don't write another one before reading these notes or before reading thoroughly about relativity. For politeness, if for no other reason, please read and understand what Einstein said before you say what he said, and then proceed to contradict it. (See references.)
Suppose that you have something new and important to say in physics. There are (at least) three things that you must do, and which the people who write pointing out these "errors" usually do not do.
If you want to surpass the limits of established knowledge, you must usually understand those limits so that you can see how (and if and where) they may be surpassed, and whether there is a reason to do so. You should aslo read and understand the experimental results. Quite often, those who claim to have disproved relativity are contesting not the theory, but experiments. They write telling me what the experiments showed have shown, rather than what they did.
The principle of correspondenceThe relation between old and new theories in physics is an important scientific principle called the Principle of Correspondance, widely used with quantum mechanics and relativity. In that context, it may be stated thus: Newtonian physics (NP) is spectacularly succesful over a huge range of physical problems. Any theory which replaces NP must give results which are virtually identical to those of NP for all of these problems, otherwise the new theory is immediately falsified by the past experiments that agree with NP. QM and relativity must agree with NP in all such problems. (They do.)
Let's apply the principle again: any theory which attempts to replace the current theories of Electromagnetism, Quantum Mechanics or Relativity would have to agree very precisely with the current theories in all of the cases where these theories are in good agreement with experimental observation. Because these theories are in very good agreement in every experiment so far made to test them, a new theory can really only differ substantially from these results in cases where we haven't yet measured. For instance, Gravity Probe B is designed to test among several theories of gravitation (one of them being the General Theory of Relativity). These theories all give almost exactly the same results for falling apples, precession of perihelia, and gravitational lensing. They differ in predictions for something called gravitational frame dragging.
If you have a theory to replace relativity, it must first give virtually the same predictions as relativity in a huge variety of conditions, otherwise your theory is already falsified by the experiments conducted to test relativity. Ideally, it should also give different results in some conditions, as yet untested, so that we can decide between the two.
So don't tell us that Einstein was wrong without reflection, careful justification and attention to the points above.
On the other hand, this web site has been written in something of a hurry to meet a deadline: the centenary of relativity (June, 2005). If you see errors here, please let us know!