On 6/6/12 7:02 AM, Mike S wrote:
On 6/6/2012 9:09 AM, Jim Lux wrote:
does anyone have a reference to the math and process used to measure
distance from earth to sun using transit of venus?
http://transitofvenus.nl/wp/getting-involved/measure-the-suns-distance/
Of course, back in the 1700s, they didn't have nice iPhone apps to give
good time hacks..
I see that Halley's scheme relied on measuring the length of the chord
of the transit, which could be done geometrically (at least from the
drawing, it looks that way), without needing time involved.
http://www.transitofvenus.nl/halleysmethod.pdf seems to say that a
precision of around 1 second for the duration between contacts would do.
(of course, here in southern California, we couldn't do it, because
the sun set before 3rd contact)
Delisle's technique seems to require synchronized clocks. How well
synchronized?
A good math treatment of the technique would be nice to find, then one
could take known clock and measurement accuracy and figure this kind of
thing out. I think this has more of the info
http://www.venus2012.de/venusprojects/contacttimes/basicidea/basicideatimes.php
but I'm still looking through it.
I'm also interested in how did they get their "absolute time" hack for
the Delisle technique.
It's an astronomical measurement, so maybe the lunar distances or Jovian
moons approaches would work, but then you have to have a stable enough
clock to last from night until day.
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