A reminder that the transit of Venus across the Sun will be visible a little over 24 hours from now (starting before sunset June 5th in the United States.) It’s the last of your lifetime, so make your plans now. Weather forecast across much of the eastern U.S. is pretty bad, I’m afraid. Of course there will be many places to watch on-line. For more information, I highly recommend http://transitofvenus.nl/wp/ . Also, though you and I can’t see Venus right now (too close to the Sun), the SOHO satellite can: click here for the latest photo, updated frequently, which shows the sun (at center, blocked out) and the sun’s corona around it, and a white dot approaching the sun, which is Venus (ignore the white horizontal lines, which are an imagining artifact).
The transit of Venus was used, historically, to figure out how big is the solar system (the sun and the planets). As I’ll explain tomorrow, it wasn’t that hard to figure out how large are the distances between the sun and the planets relative to one another, but getting the overall scale — the absolute distances — was a much harder problem. The first measurement accurate to a couple of percent came from the transits of Venus in the 1760s. I’ll explain (roughly) how this works tomorrow; the technique relies on the principle of parallax, a principle which lies behind our own ability to perceive depth, and is used by astronomers to measure distances to (relatively nearby) stars.
[Reminder: two events coming up in which I’ll be speaking:
First, a panel discussion June 7th, sponsored by SoNYC (Science online New York City), entitled “Reaching out of the Ivory Tower”, about the experiences of scientists who are reaching out to the public. (free tickets required, click here for details and tickets.) Panelists: Ethan Perlstein, Sarah Weisberg, Matt Strassler, Jeanne Garbarino. Location and time: Weiss 305, Rockefeller University, East 66th and York Ave. New York, NY, Thursday, June 7,2012 from 7:00 PM to 9:00 PM (ET)
Second, again in New York, Saturday June 16th at 2pm, I’ll be giving a lecture (click here for details): THE EINSTEIN OBSESSION: SCIENCE, MYTH AND PUBLIC PERCEPTION.]