I think it's safe to say this is an event that isn't likely to happen again in anyone's lifetime -- at least, anyone old enough to hold and use a telescope.

This evening, the planet Venus will be visible to us as it passes between us and the sun -- something that won't happen again until the year 2117.

And besides being cool, it's also an event that was of enormous historic importance to astronomers -- and continues to be of enormous importance in the present day.

Mike Reid is an astronomer at the Dunlap Institute for Astronomy and Astrophyics at the University of Toronto.