Wednesday, 6 June 2012


Venus transiting the sun, in my backyard,
projected through a handheld telescope.
Today is a special day to be an Earthican, if you are interested in more than what is in you own backyard, that is.

The 2012 Transit of Venus is a rare celestial event where Venus blazes a trail across our local star. Every 108 - 121 years, Venus crosses in front of the sun twice, with about eight years between passes.  If you missed it, well, start dieting, exercising and living healthily because the next one won't be until 2117.

There are two stories about the transits of some 240 years ago that I like.  Scientists of the day were attempting to measure the distance to the sun using parallax and they needed measurements from around the globe to perform their calculations.

The first story is of Captain James Cook setting sail for Tahiti to observe this event. After lazy cocktails and basking in the sun, he opened sealed orders informing him that he was to search for the fabled land of Terra Australis.  And by skipping a few pages of the history book we end up with me tapping away on my keyboard on Australia's Eastern coast.

The second tale is not so happy.  It is of the misfortunes of Guillaume Le Gentil.  A Frenchman who was to observe the transit from Pondicherry, India.  On his sea voyage, war broke out between France and England (shock!) and when he arrived at Pondicherry he found it had been taken by the English.  The English forced himout to sea and he set sail to Mauritius. On the day of the transit he couldn't take any readings because of the rolling and banking of the ship.

He decided to take readings of the 1769 transit in Manila and filled the intervening time mapping the east coast of Africa.  When in Manila, the Spanish weren't welcoming so he set sail for Pondicherry once more.  Pondicherry was once again under French rule after a treaty in 1763.  He built an observatory and patiently waited the transit.

The weather was fine in the days leading up to the transit but the skies clouded over the whole day of the transit.He took no measurements.

But it gets worse!  The return trip was plagued by delays; storms, dysentry, unsettled humors.  He made it back home some eleven years after his departure.

But it gets worserer!  In the intervening time he had been declared legally dead.  His wife had remarried and his greedy relatives had picked apart his estate.  He had even lost his seat on the Academie des sciences.

He did remarry, reclaim his job at the Academie and lived a few more decades.  I bet he's glad that the next transit wasn't going to be until 1874!

No comments:

Post a Comment