Our brains evolved long ago to see patterns in nature—which turned out to be good way to find food and avoid being eaten—and down through history, humans have defined patterns of stars as a way of providing some order to the chaos of the night sky.

You might see a big dipper, but really these patterns are just how the stars appear from our current position in space. They appear to be close to each other, when in fact some are quite close to Earth and others are tens, if not hundreds of light-years away. Indeed, the stars in most constellations are nowhere near each other in three-dimensional space, they just appear close together on what looks to us like a two-dimensional sky.

At the same time, stars on opposite sides of the sky might actually be quite close to each other, with Earth in the middle.

From Earth, you really can't tell if any two stars are anywhere near each other. If you could fly out far from Earth, however, it would be easy to see their true relationships.