Uh oh: the entire universe is running out of gas

You probably didn't know that the universe runs on gas. You also probably didn't know that the universe is rapidly running out of gas, and galaxies have been slowly dimming like spent flashlights. Should you panic? Yeah, I'd say so.

In order for new stars to form, they need gas. Being environmentally conscious, stars insist on a large supply of molecular hydrogen. Unfortunately, the supply of molecular hydrogen in the universe is fixed, and over its life cycle, a star will turn about 70% of its hydrogen into something else. Like, you know, planets and people and stuff. Over time, galaxies burn through their hydrogen supplies, and new stars form less and less frequently.

To get more fuel, galaxies depend on gas being drawn in from intergalactic space. And there's a lot of hydrogen floating around out there: it's estimated that two-thirds of all the gas in the universe is currently located between galaxies. Problem is, the universe is expanding, and when you've got a fixed resource in an expanding area, the density of that resource drops. Or in this case, it plummets, and galaxies have been having a harder and harder time of it for the last ten billion years or so. We can blame this expansion on Dark Energy (whatever that is), but there's no way to stop it, and it's just a matter of time (a very, very, VERY long time) before the last sun in the entire universe quietly winks out.

CSIRO, via Physorg