Death from the Skies! (48 page)

There will still be planets; they will orbit white dwarfs and brown dwarfs, and probably many more will wander the Universe after being ejected from their home stars during planetary formation. However, planets don’t generate energy, so they aren’t of much interest to us here. They’ll be frozen solid.

Binary brown dwarfs are common: two brown dwarfs in orbit around each other. Owing to some weird effects of Einstein’s relativity, the orbits of the objects will slowly decay with time. For a typical pair, the two objects will collide after about 10
¹⁹
years, which is in the Degenerate Era. A merging of two brown dwarfs this way will almost certainly create a disk of material around them in the same way as an off-center collision would. This may be a “common” event during this era.

Astronomers use the term
collision
to mean any encounter where two or more objects interact with each other through gravity, and not necessarily to mean direct physical contact like a car crash.

Unlike smaller black holes, which will tear a star apart because of tidal forces, a supermassive black hole’s tides are far, far smaller, so stars will get eaten whole. There will be no accretion disk, and so no light emitted by the consumption of a star. Eating gas clouds, on the other hand, still will cause the black hole cosmic indigestion.

We don’t have to wait that long to see one decay: if we collect enough together, say 10
³⁷
of them, then we should see one decay every year. This has been attempted, and still no protons have decayed while scientists watched. If the decay time is off by a little bit—say it’s 10
³⁸
—then this makes the process more difficult to detect . . . but 10
³⁸
years is still small compared to the time we’re talking about in this chapter.

Or whatever non-proton-based food they eat while watching movies.

Because of the bizarre nature of degenerate matter, lower-mass objects actually increase in size when they lose mass, the opposite of what we expect. White dwarfs start out roughly the size of the Earth, but in 10
³⁹
years or more, they’ll actually expand to be as big as Jupiter.

This released energy mostly gets converted into sound (footsteps) and motion (momentum as you travel down).

Yes, I had to look up those two words.