I Didn’t Know That

Q: What is the farthest the naked eye can see in the nighttime sky?

A: On a smoggy night in Los Angeles, about 200 yards, according to Neil de Grasse Tyson, director of the Hayden Planetarium. On a clear night, however, one could expect to see the Andromeda galaxy, which is 200 million light years away. Its 300 billion stars appear as a fuzzy little patch in the constellation Andromeda. All other visible objects in the sky are part of our own Milky Way galaxy and are at most a few thousand light years from Earth.