How do astronomers know how far away stars are? Unfortunately, it’s not a short and easy answer.

Over the many years I’ve been writing this column, I've rattled off the distances to many celestial objects. I don't often ...

Extra stellar systems are so far away from our own that we couldn’t even hope of developing a tape measure long enough to determine how far away they really are. On the other hand, astronomers can ...

Try this experiment: extend your thumb at arm’s length and close one eye at a time. Your thumb will seem to ‘jump’ between two positions as you switch the eye that is closed. That jump is known as ...