E and mc2: Equality, It Seems, Is Relative nytimes.com
[ This may or may not have anything to do with Michelson-Morley. I could sorta understand special relativity, but general relativity was quite beyond me. clip: ]
To some physicists, however, the very idea of variations in the speed of light in a vacuum — the c in E=mc2 — is meaningless. The miles and seconds by which speed is measured are human inventions, they point out, defined in fact in terms of lightwaves, so the whole notion of the speed of light varying is circular. In the last analysis, they point out, all physical measurements boil down to a few dimensionless constants like the fine structure constant, alpha. "What we measure objectively is whether alpha varies," said Dr. Michael Duff of the University of Michigan in an e-mail message.
Dr. Magueijo said those criticisms were technically correct but said the speed of light was one factor of several in the formula for alpha. So if alpha varied, as some astronomical measurements have suggested, one could choose to think of it as a variation in the speed of light, of electric charge, or even a variation in another number known as Planck's constant — or all three — if that made the math simpler. "It's a matter of convention," he said, adding, "you make the simplest choice."
Despite all the activity, scientists agree that they are mostly in the dark about the deeper consequences of these conjectures. "Some may eventually be developed to the point of being a credible alternative to relativity," conceded Dr. Kostelecky, saying that he suspected that others might not really change relativity or might have already been excluded by existing experiments. Without a systematic analysis it was impossible to know.
Dr. Amelino-Camelia said that the doubly special theories preserve Einstein's principle that all motion is relative, but at an unknown cost to the rest of physics."We paid a dramatic price for relativity: the notion of absolute time," he said. "This time it is not completely sure what is the axiomatic principle we have to give up."
Dr. Albrecht urged caution and said physicists needed guidance from experiments before tossing out beloved principles like relativity. "The most dignified way forward," he said, "is to be forced kicking and screaming to toss them out." |
