eratosthenes
esiegel | June 19, 2012"Soon the earth will tilt on its axis and begin to dance to the reggae beat to the accompaniment of earthquake. And who can resist the dance of the earthquake, mon?" -Peter Tosh
Every year, there are two special days where every place on Earth receives the same amount of sunlight -- 12 hours -- split evenly between night and day: the equinoxes!
Image credit: timeanddate.com.
Like all known objects that revolve around another due to gravity, the Earth rotates along its journey around the Sun. But on those two days of the equinox (from the Latin, meaning "equal nights"), the Earth's axis-of-…
rallain | December 28, 2009One of things I like to think about in science is "how do we know that?" It is interesting how one thing builds on another. This is a story of how the Greeks estimated the distance from the Earth to the Sun (an important idea in the development of the model of the solar system). I like this story because it is not too complicated. In fact, one could easily reproduce these measurements themselves. So, here is what I will talk about:
Measuring the size of the Earth.
Determining the distance from the Earth to the moon and the size of the moon.
Calculating the distance (and size) to the Sun.…