¡SkyCaramba! weekly astronomy blog for the week ending June 9, 2012
I hope you get a good safe view of the transit of Venus on June 5 and 6 (the date depends on which side of the International Date Line you’re on). I know as well as you do how a cloudy sky or being on the wrong side of the earth can ruin the fun. In case you don’t get to enjoy it, I thought this would be the ideal time to tell you about some upcoming transits. They don’t happen often, and I don’t expect to see most of them. But knowing what’s happening is half the fun, so the weather and your location can’t ruin the whole thing!
The next time people on Earth will get to see Venus cross the face of the sun will be in 2117. Today’s medical scientists are working on ways to greatly extend human lifespans. If you think your chances are good, plan a trip to Australia or Malaysia for a really good view on December 11 that year.
Space scientists are also working on ways to get people to Mars. If they’re successful by 2030, humans may see a transit of Venus from the red planet by August 19 that year. There’ll be another one on June 18, 2032.
Jupiter is a less habitable place for people. We’re certain not to make the deadline to see the next transit of Venus from Jupiter anyway. It’s on September 20, 2012. May 26, 2024 is a long shot too. I’m not counting on November 14, 2030 either.
It’s too bad Saturn’s even harder to get to. There was a transit of Venus there on May 6 and another one will happen on December 21.
Six transits of Venus will occur during a three year period for an observer who could be on Uranus starting September 22, 2028.
And from Neptune, Venus will cross the sun 11 times in the middle of the 21st Century. The first of those is on October 27, 2042.
Today, when a planet transits the sun, it’s a curiosity that gives the astronomy community a chance to make the public interested in science. But in the 1700s and 1800s, transits of Venus were of such serious scientific interest, astronomers traveled a long way to observe it and measure it every way they could.
Edmond Halley had shown how astronomers in different places could time a transit of Venus to figure out how far away Venus is from Earth. Science had already shown the proportionate distances of the planets. If someone could obtain an exact measure of one of them, the rest of the distances could be calculated too.
Getting those observations was easier said than done in the days before airplanes and vaccines. Wars didn’t help either. Today, you can enjoy a simulated view of a transit from your computer using mathematics already perfected.
http://www.skyandtelescope.com/observing/highlights/Transits-of-Venus-in-History-1631-1716-156303125.html has a wonderful history of observing transits of Venus.