'Faster Than the Speed of Light': E = mc², Except When It Doesn't nytimes.com
[ This is actually a book review, and it seems that the author is pretty much off base, according to just-in research, to be noted in the next message. excerpt ]
Consider the horizon problem, a staple of popular science books. Look out (with a suitably powerful telescope) at a galaxy 10 billion light-years away. According to the logic of the Big Bang theory, the light was emitted 10 billion years ago and is just now reaching this part of the universe.
Now turn around and look 10 billion light-years in the opposite direction. You have successfully observed two regions of the universe that themselves are 20 billion light-years apart. Since the whole universe is only 15 billion years old, they will never be able to see each other or (since nothing travels faster than light) interact in any way.
The weird implications of this become clearer if you imagine the earliest moments of the Big Bang. When the universe was a second old, and hence a light-second in radius, about 186,000 miles, opposite points on the circumference were twice that far apart, unbridgeable even by light. No matter how far back you go -- a millisecond, a microsecond -- the regions can never have been in contact. It is as if they exist as two separate universes.
The reason this bothers cosmologists is that, so far as they can tell, the universe in front of us and the universe behind us are pretty much the same. They differ in detail, of course -- this galaxy here, that constellation there -- but in the most general sense, creation appears to be homogeneous. Galaxies are distributed in a more or less uniform manner, and in whatever direction you point a thermometer, space is the same temperature. But if certain parts of the universe never interacted, then why is there so smooth a blend?
The favored explanation is a theory called cosmological inflation: suddenly for a few moments early in its history, the tiny universe began wildly expanding, far more rapidly than it does now. Those now isolated regions were originally close enough to touch.
Some theorists find this a bit contrived, and Magueijo is one of a handful proposing a different solution: if the speed of light used to be faster, then neighborhoods that now seem hopelessly far apart were originally together.
Those are the bare bones of the idea, which Magueijo elaborates throughout the book. Whether that notion is any less ad hoc than inflation is a matter of taste. Depending on how future experiments come out, his theory will one day be recorded as a stunning breakthrough or a forgettable detour down a cul-de-sac. |
