This morning I had the opportunity to witness an astronomical phenomenon called the Venus Transit. Below is an excerpt from the National Geographic website: Transits happen when a planet crosses between Earth and the sun. Only Mercury and Venus, which are closer to the sun than our planet, can undergo this unusual alignment.
With its relatively tight orbit, Mercury circles the sun fast enough that we see the innermost planet transit every 13 to 14 years. But transits of Venus are exceedingly rare, due to that world's tilted orbit: After the 2012 Venus transit, we won't see another until 2117.
The effect won't be visually impressive, but that black dot against the sun is a remarkable thing to see.