If this were some 1950s sci-fi thriller, the Doomsday Cloud would loom dark and ominous in the evening sky. Each night more stars would wink out along its edges. The cloud would sweep past Jupiter, swallowing it whole, and race on toward Earth. There would be an inky darkness at noon. And so on.
No, nothing is going to blot out the sun. But recent observations and numerical simulations suggest that eventually—in a few millennia, maybe—the solar system may plow into a cloud of gas and dust a thousand times denser than the space we travel through now. This interstellar fog could reduce the sun’s sphere of influence until most of the outer planets are sitting naked in space. Dust and gas will penetrate as far as Earth’s orbit and may begin eating away at the oxygen in our upper atmosphere. The solar wind, now greatly compressed, will no longer provide adequate protection from the high-speed electrons and ions ripping through space. These cosmic rays will tear into the atmosphere, to the detriment of the delicate molecules of life.
