Last chance for the next 105 years!

Tomorrow, June 5th, is our last chance to see a transit of Venus until the next one occurs, 105 years from now - by which time I daresay most of us will no longer be interested!  Smithsonian.com reports:

Every century or so, something truly special happens in the sky, and it happens twice: Venus passes in between the sun and earth. The transit of Venus, as it’s called, comes in pairs spaced exactly 8 years apart, with each pair separated by gaps more than 100 years long. As a result, only 8 transits have occurred since the invention of the telescope.

The most recent one was in 2004, and the second half of the pair is next week, during sunset on June 5th for North American observers, and during sunrise on June 6th for many in Europe and Asia. After this, the next one isn’t until 2117.

Transit of Venus in 2004 (image courtesy of Wikipedia)

Why does it happen so rarely? Two events need to occur at the exact same time for us to see a transit of Venus. First, Venus needs to pass between us and the sun, so that to an observer looking down at the solar system, all three bodies would be in a straight line. This happens every 584 days.

However, Venus also needs to line up vertically so that it appears somewhere in front of the face of the sun from our vantage point. Because Venus and the earth don’t orbit the sun on the exact same plane—Venus’ orbit is tipped 3.4 degrees relative to ours—most of the time it’s too high or too low ... It only lines up in all 3 dimensions and traverses across the sun four times during an unusual 243 year cycle, with the transits coming in pairs separated by alternating periods of 121.5 and 105.5 years.

In the United States, the transit will begin at roughly 6:04 Eastern, 5:04 Central, 4:05 Mountain, and 3:06 Pacific Time. Over the course of several hours, Venus will appear as a small dot moving slowly against [the] backdrop of the sun. As with a solar eclipse (or anytime, really), looking directly at the sun can severely damage your retinas, so you should use a special filter or simply project the sun onto the ground or a piece of paper, by holding up a piece of cardboard with a small hole punched in it and allowing the sunlight to pass through.

There's more at the link.  Bold print is my emphasis.

I guess I'll have to keep my eyes peeled for that.  If I'm going to be long dead by the time the next one comes around, I may as well make the most of this opportunity!

Peter