Astronomical observations of days gone by

There is a book by Canadian astronomer Don Fernie, “The Whisper and the Vision,” where he describes trips made by early astronomers

 

Outside, rain is falling from a leaden sky, and it looks as though it will continue for the rest of the day. As I write this, the transit of Venus is half over, and there is no sign the weather will clear. Things do not look good for seeing today’s transit of Venus, the last for more than 100 years. Hopefully others across Canada will have more luck.

A cynical possible consolation is that in the past others travelled halfway around the world to see transits of Venus, and instead of seeing Venus moving between them and the Sun, they saw clouds.  We’re seeing the same thing without the inconvenience of having to travel.

There is a marvellous book by Canadian astronomer Don Fernie, called “The Whisper and the Vision,” in which he describes trips made by early astronomers to make important observations. One of the astronomers mentioned in the book is Guillaume Le Gentil.  Born in 1725, Le Gentil showed great potential as an astronomer and was elected to the French Academy of Sciences. He was the one picked to travel to Pondicherry in India to observe the 1761 transit of Venus, to measure the precise distance of the Sun and establish the scale of the Solar System. He set sail in early 1760. When he arrived at Isle de France he heard that Pondicherry was besieged by the British and he would have to wait until the siege was lifted.

He hitched a ride to Pondicherry on a troopship loaded with French reinforcements. However a series of storms blew them off course and the day of the transit found Le Gentil in the middle of the Indian Ocean. He was forced to observe the transit from the rocking deck of a ship and could make no useful observations because his clocks and other instruments needed firm ground under them.

Rather than fight his way back to France and then out again for the second transit of the pair, which would happen in 1769, he decided to travel directly to Manila in the Philippines, where his calculations indicated would be an ideal place to observe it. He laboriously made his way there, set up and let the Academy know what he had done.  He got an angry reply, telling him to get back to Pondicherry. Since the Academy was paying, he reluctantly obeyed.

On the day of the second transit there was a huge storm, with high winds, clouds and rain. He got to see nothing of the transit at all. What added to his misery was the news he received later that observing conditions had been ideal in Manila.

Enduring hurricanes and storms, he finally got home in 1771, only to find that he was believed to have died on his travels, and his estate had been ransacked by family members and those claiming to be his creditors. It took a long and expensive court battle to get at least some of his property back. However, the Academy awarded him a special position and he lived out the last 20 years of his life in relative peace. He died in 1792, escaping the French Revolution and probably the guillotine by a few months. There is no question that we astronomers have an easier time of it today.

Mercury is low in the west after sunset. Mars and Saturn dominate the southern sky. The Moon will be new on the 19th.

 

Ken Tapping is an astronomer with the National Research Council’s Dominion Radio Astrophysical Observatory, Penticton.