I had a once in a lifetime chance to see the Transit of Venus, not only that I saw it on a rooftop in Athens, Greece. Aside from its rarity in occurrence, a transit of Venus is important for many other reasons. The first recorded observations of a transit of Venus was made by Jeremiah Horrocks from his home near Preston in England, on December 4, 1639. His friend, William Crabtree, also observed this transit from Broughton, near Manchester, England. There have only been 5 other transits of Venus recorded in history, hence why scientists scoured the globe to be able to view it back in the 1700s and 1800s.
If Venus and the earth orbited the sun in the same plane as the sun, transits would happen frequently. That means that the planets are in slightly different planes. Venus' orbital plane intersects that of the Earth at only two points along its orbital path. When the planet lies at either one of those two points, and when it catches the Earth too, it appears to inch across the solar disk, as we viewed it on the morning of June 6th.
Transits of Venus occur in a strange pattern. The last transit occurred in 1886, then again in 2004, and then 8 years later in 2012, and the next one will not occur until 2117. So the transit pattern is 121 ½ years, 8 years, 105 ½ years, 8 years. They occur in eight year pairs because the length of eight Earth years is almost the same as 13 years on Venus, so every eight years the planets are in roughly the same relative positions. Something similar happens with our moon, when every month the moon passes between the sun and the earth, yet we do not see a solar eclipse every month..
To view the transit of Venus, we took a box and covered the opening with paper. We poked a hole through the top of the box. This made our own camera obscura. We held the side with the hole up to the sun and projected the shadow onto another piece of paper straight in front of us. It worked well once we got the hole adjusted by making it larger. We also used binoculars to project the image onto the same piece of paper held in front of it. This way was easier to view the transit. Using these methods, we could safely view the transit without looking at the sun directly.
Getting up at 6 a.m. to view this event was definitely worth it, even more worth it when you’re on a rooftop in Athens, with a view of the Parthenon on one side and watching the transit (safely) as well! I wouldn’t have missed it for the world, because I’ll never get to see another one in my lifetime!