From the Archives: Venus Transit Edition

I found this on my old blog from 2012, and it seemed interesting and relevant, and worth re-posting.  Enjoy!

Did you watch the Venus Transit this year?  You know, when Venus’s orbit makes it appear that it’s going across the sun, and it happens every 110 years or so?  Well, that’s not entirely accurate.  It happens in pairs – just a few years separating each one, and then nothing for another 110-ish years.  We watched it through the clouds in New York City in June when I was there for BookExpo.  We went to a spot along the waterfront where they had telescopes, and even though I couldn’t see much, it was cool to see something so historic.

But three hundred years ago people took it way more seriously.  I’m reading this book about it, Chasing Venus.  So apparently Edmund Halley (of Comet Fame), in the late 1600’s, heard a story about an astronomer who had seen Venus when it crossed in the mid-1600’s.  Telescopes were just brand new then, so most astronomers didn’t have access to them.  So Halley starts doing some advanced math, and he decides that if you get enough people to go out into the world, in all different places to measure the times of the Venus transit – ie when it crosses in front of the sun, and when it leaves – that you can figure out how far the sun is from the earth.  And do some more calculus, and you can figure out the size of the universe.  Which was a really big deal back then.  Now we know the universe is Really Big, and Expanding, so we don’t worry too much about it.  But Halley was super concerned about it.

He talked to a young astronomer, Delisle, and made him promise that even though Halley wouldn’t be alive for the next transit, he (Delisle) would spearhead putting together a panel of astronomers who will go all around and take these measurements – he even outlined what measurements you needed to take, and how to do it.

Fast forward to 1761, and the Seven Year’s War is going on (we know it better as the French and Indian War) and these scientists from France, England, Russia, Prussia, Sweden and even the American Colonies are all trying to coordinate sailing through hostile seas in the middle of a war to watch Venus.  I won’t give away the story, but suffice it to say that they learned a lot, and by 1769 (the war was over by then) when the second of the pair of transits came around again, the scientists decided they needed to go even further, to the South Pacific, and they wound up finding Australia.

The main point in summation: in the middle of a giant world war these people traveled through the arctic on sleds, through treacherous roads, in hostile seas, risking their life to watch a little dot move across the sun so that they could figure out how big the universe was.  And all because an old guy in Paris told the Paris Academy that Edmund Halley told him that he once heard of a guy who had seen the transit a hundred years before.  Seriously?  Would you risk your life on a story like that?

And here I could barely get myself to the pier to watch it through a telescope a few months ago.

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