ASTR100 Exam 2

James C. Hunt ASTR100 Ex2 UMD CP

Proof the earth is round

Ship sailing into the horizon, earth’s shadow during lunar eclipses, different stars visible at different latitudes

Eratosthenes

Librarian of Alexandria, figured out the circumference of the Earth

Antipode

Exact opposite spot

Zenith

the exact point above your head on the celestial sphere

Nadir

Opposite point on the celestial sphere

Horizon

Right between zenith and nadir

North celestial pole

North Pole zenith

South celestial pole

South Pole zenith

Celestial equator

Between north and south celestial poles

What direction is earth’s spin from the north pole

counterclockwise

What direction do moons orbit in

Counterclockwise

North star

Polaris - almost right over the North Pole, North Star changes during earth’s wobble

Precession

Earth’s 26k year wobble

Why does the precession happen

Earth forms, molten and spinning, not an exact sphere/bulge at the equator, sun and moon pull on earth unevenly with gravity, discovered by newton