If you're still giddy about the annular solar eclipse we had a
few weeks ago, you'll be happy to note that an even rarer
astronomical event is coming up Tuesday, and it's a sight that
no one alive today will ever see again (unless they solve that
whole aging problem, or someone will make it to about 120 years
old.) Tuesday evening, those across North America will be
treated to the "Transit of Venus" -- or when the planet Venus
will cross directly in front of the sun. Unlike the moon, whose
size relative to the sun can cover up the whole thing, Venus in
relative size is about 1/32nd the size of the sun. So it'll be
equivalent to a small dot moving across the sun. So small that
trying that pinhole viewer that you might have put together for
the annular eclipse might not have enough resolution to pick up
Venus moving across the sun. (And yes, same eclipse safety
"Don't look at the sun!" viewing rules apply to looking for
Venus.) According to NASA, the transits of Venus are quite rare,
coming in pairs 8 years apa