Eureka! I think I got it!

After an enthusiastic start at the beginning of the year I have carried on reading science books in a desultory sort of way - I have started several books but not finished them. I am now reading A Short Histoy of Nearly Everything by Bill Bryson ... which comes close to living up to its title. It is certainly wide ranging. I think (only think, mind you) that courtesy of Bill I have finally understood - in a vague sort of way - something that has eluded me whenever I have come across it before.

Fanfare of trumpets ... I think I get - almost - vaguely - the theory of relativity! Not that I understand how it all works, I just think I now know what it is. Earlier this year I read part of The New World of Mr Tompkins by George Gamow and Russell Stannard, and made it through the special theory of relativity before stumbling into a morass with the general theory of relativity and drowning. But now I have it! Maybe.

Speed is limited. Nothing can go faster than the speed of light. The closer something approaches that speed, the more distorted it becomes in both appearance and time - it appears both shorter and slower than it really is. This distortion is relative - only the onlooker travelling at a different speed can perceive it. That is the special theory of relativity.

The general theory of relativity works much the same way except that you have to add in an extra dimension so that everything is relative to everything else in both space and time. This fourth dimension is known as "spacetime" and provides a kind of intangible fabric that holds everything in the universe in a relative web. You can imagine the universe as a "saggy mattress" in which all things create their own dent, causing anything nearby to roll down into that dent, unless it has a bigger dent of its own. Of course, these are only relative dents, not real, tangible ones, but ... hey presto! You have an explanation for gravity! You also have an explanation for all sorts of measurable but intuitively improbable (or impossible) effects in space and time. I think.

My brain hurts. But after all that mental effort I thought I'd share the fruits of it. If there is anyone out there who is a science minded person ... have I got it right?