The Transit Of Venus? This Can't Be Good For Anyone

Because some numnut will hear the story and look directly at the sun for an extended period of time hoping to see something spectacular.

There have been only seven transits of Venus since the invention of the telescope in 1610, according to NASA. They occurred in 1631, 1639, 1761, 1769, 1874, 1882 and 2004.

Captain Cook and the Transit of Venus

The 1769 transit was an especially historic one. Several decades earlier, astronomer Edmund Halley realized that by observing the transit of Venus, scientists could finally crack the question of the absolute size of the solar system. At this time, astronomers knew the distance of the planets to the sun as fractions of Earth's distance to the sun, but they had no idea of the absolute distance. Venus could have been a million miles away or a billion.

Halley figured out that by having one person measure the transit of Venus on one side of the planet and another do the same on the other side, scientists would be able to triangulate the absolute distances involved. In 1768, the famous British explorer James Cook set sail for Tahiti to make this crucial measurement.

Look skyward, space-lovers: Tuesday, June 5 is the last chance in your lifetime to see the transit of Venus across the face of the sun.

Venus won't visibly pass between the Earth and the sun again until 2117, so get your special sun-viewing glasses now. In North America, the transit will start in the hours before sunset on June 5. Viewers in Asia, Australia, Africa and Europe can catch the transit at sunrise on June 6. The transit will begin at about 6:03 p.m. EDT, 5:04 p.m. CDT, 4:05 p.m. MDT and 3:06 p.m. PDT.