h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

If galaxies further away are receding at a greater speed, this does not mean that if we go far enough, they will be receding at the speed of light. According to Special Relativity, they will be receding at a speed which approaches c, but never actually reaches it. So they won't actually be cut off from us, will they?

The expansion of space itself is not limited by lightspeed, since the Galaxies are not actually moving faster than light, the expansion of the space between us just makes it look that way.

If space were expanding at a rate of 10% per second, a thing 1 meter away would br "receding" at 10 cm per second. A thing 1 km away would be "receding" at 100m per second. Light travels at 300,000 km/s, so anything at a distance of 3 million km or more will "receding" faster than light, and hence will be beyond the de Sitter horizon.

Another place you'll see apparently faster-than-light expansion is in the inflationary model of the Big Bang, in which the Universe is supposed to have expanded from the size of an atomic particle to roughly its current size in an eyeblink.

Hed

Whose eye was that, blinking?

God's?