But the basis of the theory of relativity was an empirical fact: that the speed of light appeared to be constant in all directions. The theory of light waves traveling through an ether (like sound waves through air) suggested that we would be able to find the earth's speed relative to it, by measuring the speed of light. But that wasn't what people were finding...
A lot of the really smart theoreticians today don't seem to be basing it on new empirical facts, they're just making clever theories up. Clever people like to do that. Of course, it's not their fault if there aren't any mysterious facts that don't fit current theories - but that's the place to start.
What about the total incompatibility between general relativity and quantum mechanics? Each works incredibly well in its sphere, but the "fact" is that they both describe the same universe and there is obviously something missing between them. There have been several attempts to develop a common framework, superstrings just being the latest, but so far none have been really useful or convincing.
That's just the thing. There is a total incompatibility between general relativity and quantum mechanics, but it's currently a theoretical problem. AFAIK there's no current experiment (coming from an accelerator or an astro. survey) that fundamentally requires it to explain its results (ducks). The latest and greatest was WMAP, and inflation seems to explain that data. (This doesn't mean that a potential theory of QG could not make predictions that one could test tomorrow.) Most papers are speculatory ("We think ... Future surverys will confirm (or deny) our theory...").
The interesting thing is that there is stuff that is (indirectly) observed and actually part of the modern framework of cosmology: dark matter and dark energy. Modern cosmology says that for every pound of regular stuff there is 5x dark matter and 14x dark energy, so it'd be important to figure out what it actually is. As one of my elderly professors put it, "I hope to live long enough to learn what this stuff actually is; my friends always ask me what it is, and I my answer at the end is always 'I don't know'." There are current experiments that try to detect dark matter particles (in cosmic radiation I think), but they don't seem to get a lot of attention, maybe if they find something.
I don't think there's a problem between the two when Cramer's transactional interpretation is used for quantum mechanics. I seriously think the answer will come from something derived from his work.
I wonder if he's the same physicist John Cramer that has written a couple of SF novels; John Cramer's novel "Einstein's Bridge" is excellent hard-hard SF.
No. The only times when both quantum+special relativity (quantum field theory) and general relativity are both "in effect" are immediately after the big bang. IIRC the time-scale is something like 10^(-20s) after the big bang. It is only of importance in cosmology and at very high energies. Unless, of course, we're missing something...
That said, we could have asked, in the 19th century, is there any practical consequence of electricity and magnetism being the same force?
Although relativity was based on an empirical observation, Einstein is also famous for his theory predicting additional, as-yet unobserved phenomena.
From researching this thread today, I learnt that a similar thing happened when Hertz discovered radio waves: they were predicted by Maxwell's theory (which was based on an observation by Faraday):
> When Faraday discovered that a magnetic field can affect the polarization of light, he proposed in 1845 that light may be waves in the lines of force of electromagnetism.
> [...] In 1864 James Clerk Maxwell followed up Faraday's ideas with mathematical formulas that described light as waves of electromagnetism and that implied other forms of electromagnetic waves. Maxwell's work was experimentally verified in 1888 when Heinrich Hertz, following a suggestion from George Francis Fitzgerald, discovered radio waves by directly applying Maxwell's formulas.
But the basis of the theory of relativity was an empirical fact: that the speed of light appeared to be constant in all directions. The theory of light waves traveling through an ether (like sound waves through air) suggested that we would be able to find the earth's speed relative to it, by measuring the speed of light. But that wasn't what people were finding...
A lot of the really smart theoreticians today don't seem to be basing it on new empirical facts, they're just making clever theories up. Clever people like to do that. Of course, it's not their fault if there aren't any mysterious facts that don't fit current theories - but that's the place to start.