The universe is expanding - you knew this, right? If you've ever paused to think about this, even if only for the briefest of moments, you've probably pictured something like an explosion, where all the stars are rushing away from each other through space. This, I have recently learned (or more likely, due to my erratic memory, re-learned) from the book I'm currently reading - Pippa Goldschmidt's "The Falling Sky" - is wrong. Let me repeat that, because it's quite startling.
This mental picture is wrong.
The universe is indeed expanding. Stars, galaxies and all the other denizens of the stellar dark are flying apart (and at an increasing rate, too, thanks to the mysterious dark energy). They are not travelling through space to do this, however.
Space itself is expanding.
Think of a semi-inflated balloon with spots upon its surface. When you further inflate the balloon all the spots recede from each other. Now transfer that process to three (or more) dimensions. If you can do that then you're a better imagineer than I.
Move along now, nothing more to see here. But hopefully something to think about the next time you look up.
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