Did I ever tell you...............................

.....................that Edwin Hubble is one of my heroes?

Astronomers believed our Milky Way Galaxy was the universe until 1923 when Edwin Hubble discovered two variable stars in the Andromeda "nebula" useful for precise distance measurements. At 900,000 light years away it could not be part of our galaxy, it too was a galaxy.

A few years later Hubble discovered the farther a galaxy was from us, the faster it was receding from us, which suggests the universe is expanding. Hubble resisted this interpretation but Einstein immediately saw it was predicted by his theory of relativity, minus the fudge factor he'd entered by hand. The rate at which the universe is expanding is known as the Hubble Constant. But not known until very recently, the rate is accelerating.

-as cut-and-pasted from here.   I don't question that the Universe is expanding, but I am curious about what exactly it is expanding into.