The end of the universe in two poems

To make matters even stranger, preliminary results from some observations of distant galaxies suggest that not only will the universe not collapse, but the expansion will accelerate over time, with the galaxies flying ever faster apart. At any rate, it looks more and more like the universe will indeed expand forever. This raises a lot of interesting questions. With the Big Crunch idea, there was a definite end, with everything getting hotter and denser until matter itself broke down into a firey subatomic soup. But what happens when you leave the universe to run down over a vast span of time?

For starters, the galactic neighborhood we know today won't be around for all that much longer. Galaxies are constantly interacting and colliding with each other, forming larger, blob-shaped super-galaxies. Several nearby large elliptical galaxies have been caught red-handed swallowing up smaller galaxies, and we'll collide and possibly merge with the Andromeda galaxy in a few billion years.

On an intergalactic scale, we'll see the end of the lovely, clustered spiral galaxies of today replaced by fewer, larger elliptical galaxies. Those leftover galaxies will continue to move farther and farther away from each other, until each one is functionally alone in the void of space. Light from distant galaxies is red-shifted, meaning the light loses energy (and becomes more red) as it travels through the expanding space of the universe. Eventually, light from all the other galaxies in the sky will be red-shifted way down past visible light, through infrared, microwaves, and finally to low-energy radio waves. If people in the far future looked out into space using telescopes like ours, they wouldn't be able to detect a single other galaxy.

That might make things a bit boring for far-future astronomers, but in about 100 trillion years, things get even more dire. Stars shine by burning hydrogen into heavier elements in their nuclear furnaces. After a while, all the hydrogen will get burned up, and unfortunately, there's no new source of hydrogen for the universe. Eventually, all the stars will burn out and die, and all the raw material to make new stars (hydrogen) will be used up. No more starlight to light up the night sky.

All that will be left are the corpses of dead stars: black dwarfs (white dwarf stars that have cooled into cold, dark cinders), neutron stars, and black holes. With no more stars to warm their families of planets, environments like the Earth will disappear for good at this point, but that might not spell death for some advanced civilizations.

Science fiction authors, as well as theoretical astronomers, have begun to postulate how life might survive in this cold, dark era. There's still a lot of energy to be had by tapping into the angular momentum of rapidly spinning neutron stars and black holes. Far-future civilizations, huddling around the spinning remains of our present stars, might well look back at us in wonder. It might seem unbelievable to them that there was ever a time when abundant energy fell freely from the sky like manna from heaven.

Now we start getting into really deep time, as some astronomers are calling it. In about one hundred trillion trillion trillion trillion years (that would be a 1 with 38 zeroes after it), all the remaining mass in the universe will have collapsed into black holes. In all likelihood, there will be only one gigantic black hole left at the center of each super-galaxy, as gravity will have attracted all the smaller black holes and stellar remnants together.

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