Sorting the Solar System

	Examples	Approximate diameters(m)	Definition/Characteristic
Asteroid	Juno, Eros, Hygia	0-400	Often oblong-shaped has too small of a mass to be spherical
Planetoids	Sedna, Ceres, Pluto	400-1500	It is not large enough to have moons orbiting it and has not cleared its orbit. It must have enough mass to be spherical.
Satellites/ moons	The moon, Phobos, Europa	0-5000	Orbits a planet
Rocky Planets	Earth, Mars, Venus	1500-15,000	Orbits a star and has cleared its orbit of debris
Gas giant planet	Neptune, Saturn, Jupiter	15,000 - 200,000	A planet composed mainly of hydrogen and helium. No physical surface.
Stars	Sun, Sirius, Proxima Centauri	200,000- 1,000,000,000	a luminous spheroid of plasma held together by its own gravity. Very hot.

Gravity

F=-G*m1m2r2

F = force

G = gravitational constant (6.67408 × 10-11 m3 kg-1 s-2)

M = Mass or objects

r = Distance

With a negative mass, it would push things away.

Masses know the location of each other at all times and the force is instantaneously felt by both masses at all time.

The universe begins 13.7 billion years ago
The universe began as a single atom
The universe began as a violent expansion
Energy started freezing into matter clumps called protons, neutrons and electrons

We know the universe is expanding because the light from nearby galaxies is redder than it should be. The Doppler Effect tells us that when the distance between the observer and the source of light is increasing, the wavelength of the light also increases. So the fact that the light is redder than it should mean the wavelength of light is increasing, meaning the nearby galaxies (sources of light) are moving away from us.

Noise radiation is evenly spaced across space
The amount of radiation matched predictions
Law of conservation of energy says energy cannot be created so it must have come from somewhere

Can date the formation of the earth and the moon using rates of radioactive decay.

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