2.3 the moon, our constant companion
As the moon orbits the Earth, it returns to the same position relative to the Sun in our sky about
every 29.5 days. (origin of word month)
The moons orbit around the earth explains different lunar phases.
Phases from a
3.1 The ancient roots of science
Astronomy has been called the oldest of sciences.
Ancient people used the position of the sun/moon to tell time. Starting at 1500 BC, Egyptians
began using the flow of water to measure time through an opening of a particul
3.3 The Copernican Revolution
By the time Copernicus began studying astronomy in his late teens, tables of planetary motion
based on the Ptolemaic model had noticeable inaccuracies. He decided to try Aristarchus sun
centered idea and recognized the much s
4.2 Newtons laws of motion
Newtons recognition of gravity allowed him to bring the heavens and earth together as one
1. An object moves at constant velocity if there is no net force acting upon it.
2. F = ma or f = rate of change in
4.4 The Universal Law of Gravitation
1. Every mass attracts every other mass through the force called gravity
2. The strength of the gravitational force attracting any two objects is directly
proportional to the product of their masses.
5.2 Properties of light
Light has been argued to be a particle or a wave.
Wave has three basic properties: wavelength, frequency, and speed. Wv x freq = speed
Unlike waves we see in everyday life, light waves pass electric and magnetic fields, and so ligh
A red shirt absorbs all visible photons except those in the red part of the spectrum.
3 basic types of spectra:
1. Continuous spectrum, such as from a traditional light bulb. Contains a rainbow of
color because it spans a broad range of wavelengths wi
6.1 Eyes and Cameras: Everyday light sensors
We can analyze Earths surface and the matter on it directly, as well as the matter on surfaces and
atmospheres of worlds visited by spacecraft. Virtually all other data about the universe come to
us in the form
6.3 Telescopes and the atmosphere
Daylight and weather are the most obvious problems with observing with telescopes from the
The atmosphere also scatters human-made light and blurs images of atmospheric motion. Also,
most forms of light cannot rea
Core radiation zone convection zone photosphere corona
The second balance is energy balance between the rate at which fusion releases energy in the
Suns core and the rate at which the suns surface radiates this energy into space. This balance
keeps the ba