The Expansion of the Universe... ahem

Here's a response to my pal Yogi, who responded to my previous post with the portrait photo of Edwin Hubble:

The galaxies are like raisins randomly distributed in a loaf of unbaked dough. You bake the loaf, and it rises and expands, and the raisins move apart from one another. The raisins are not moving into new regions of formerly raisinless dough; the whole loaf, raisins and all, is expanding.

There is no space outside the universe. There is no space, empty or otherwise, outside the universe. The universe is the totality of space-time.

The universe, as Galileo taught, is "finite but unbounded." It is getting "larger" in the special sense that its constituent parts are getting further from one another -- not because they are objects moving into formerly empty space, but because spacetime (which has objects in it) is expanding.

It has emerged in the past 15 years that the universe is not only expanding, it's expanding at an accelerating rate. Nothing we know so far can explain that, and people are thrilled who prefer to work on cosmic problems like those rather than on building bigger bombs.

I am just a dilettante; literally, I take delight in it. And Saturn is two light-hours away.

Hendrix, Hubble, and Homer, folks!