Ch. 21 - Preclass 24

At first quarter it is approximately ________ week(s) until the new moon.

3

This scientist was the first to use the telescope in astronomy.

Galileo

Three laws of planetary motion were discovered by ________.

Johannes Kepler

The first modern astronomer to propose a Sun-centered universe was ________.

Nicolaus Copernicus

This scientist determined the nature of the forces that kept the planets in their orbits.

Sir Isaac Newton

Earth hits its perihelion position in January. Solar radiation is proportional to the distance squared between the sun and the earth, so why isn't it hot in "winter" at perihelion?

The ellipticity of the orbit is small, so the affect is small; seasons are caused by tilt of the earth's orbit.

Why do the planets "drift" east relative to the stars and then move west for periods of time?

They are moving in the same rotation sense as the earth around the sun, but as the earth moves faster (or slower, depending on the planet) the motion appears to be backwards.

Why were planets called "wanderers" by early Astronomers?

They move relative to the stars.

The belt of constellations through which all the planets move is called the ________.

Zodiac

One of the discoveries which led to the modern view of the solar system was that the orbits of the planets are ________

ellipses

A total eclipse of the Sun is only possible at ________.

new moon

Galileo observed several features using the telescope. Which one of the following did he not discover?

the two moons of Mars

The length of daylight on the Moon is about ________.

two weeks