What’s out there as night falls? Not down here, where owls hoot and mice scurry, but up there where first one faint light and then another appears. People have been wondering in a serious way about the sun and the moon and the stars for thousands of years. Today Rob guided an exploration of the cosmos by probing and expanding our collective knowledge.
The ancient Greeks took some significant steps forward, and some back. Anaxagoris calculated the distance to the sun and said it was just a big ball of fire, and got banished from Athens for his pains; Hipparchus turned his geometric diagram around and said that because the earth was round, not flat, that what Anaxagoris had really measured was the radius of the earth. Knowing the size of the earth enabled him to use more geometry to calculate the distance to the moon (using the time the earth’s shadow obscured it during lunar eclipses).
Macoun member Carter said that today we measure the distance to the moon by bouncing laser beams off it, and dividing the time taken for signal to return by two. Rob pointed out that you have to know the speed of the speed of light for that method to work, and suggested how we could calculate that with instruments no more special than an ordinary telescope and a stop watch. How? Well, you had to be there to join in the fun!