Earth's Motion, Lunar Phases, and Eclipses Study Guide

year

the time required for Earth to orbit around the Sun; 365.242 days

day

the time required for Earth to rotate once on its axis; 24 hours 56 minutes

month

roughly the amount of time for the moon to orbit once around Earth; 27.3 days

Ptolemy

developed a theory of an Earth-centered universe in 140 CE

Copernicus

developed a theory of a sun-centered universe known as the heliocentric model

Tycho Brahe

used a mural quadrant to accurately measure the positions of planets and stars

Johannes Kepler

stated that planets move in elliptical orbits around the Sun

Galileo Galilei

one of the first persons to observe celestial bodies using a telescope

Sir Isaac Newton

showed that planets and moons stay in orbit due to gravity

Edwin Hubble

proved that galaxies existed other than the Milky Way

William Herschel

an astronomer who discovered 8 comets and nebulae

Caroline Herschel

an astronomer who discovered several comets

Gregorian calendar

present day calendar used by most countries and will be accurate for another 3000 years

solstices

when the Sun's rays strike Earth at their northernmost and southernmost positions

equinoxes

the times of the year when day and night are approximately equal in length; 12 hours each

lunar eclipse

occurs when the Earth passes between the Sun and the Moon, casting a shadow on the Moon

solar eclipse

occurs when the Moon passes between the Sun and the Earth, blocking the Sun's light

waxing phases of the Moon

phases during which more of the Moon's near side is lit each night

waning phases of the Moon

phases during which less of the Moon's near side is lit each night

umbra

the central darker part of a shadow where light is totally blocked

penumbra

the lighter part of a shadow where light is partially blocked

revolution

the orbit of one object around another object

Orbit

The path of an object as it revolves around another object

Phase

The lot part of the moon or planet that can be seen from space

Rotation

Spinning motion

Rotational axis

the line on which an object rotates