Basics of Astronomy Outline
I. Our place in the universe
A. The modern view of the universe
1. The Sun is a star in our solar system that generates heat and light to our planet, Earth through nuclear fusion.
2. Our Milky Way galaxy is an island of stars in space with hundreds of billions of stars like our Sun.
3. The Big Bang is a theory of when the universe started expanding about 14 billion years ago.
4. The phase “looking out in the universe is looking back in time,” refers to the light from other stars we see at night happened in 1913 because light takes time to travel through space.
B. Where are we in the universe?
1. Earth’s place in the solar system is the third planet nearest to the Sun, a …show more content…
F. Galileo’s observations
1. He saw four moons orbiting Jupiter.
2. He saw Venus go through phases in a way that shows it is orbiting the Sun.
G. Laws that tell us how the planets move around the Sun,
1. Kepler’s laws of planetary motion
2. Newton’s laws of motion
H. The Earth rotates once each day around its axis counterclockwise.
1. The Earth rotates on its axis 24 hours each day.
2. When the Earth rotates on its axis on the light side it is day.
3. When the Earth rotates to the dark side it is night.
4. When the Earth tilts on its axis the seasons change.
I. The Earth revolves around the Sun as it spins on its axis.
1. The Earth revolves around the Sun 365 days.
J. The tilt of the axis causes the seasons on Earth not the changes in the distance from the Sun.
1. The summer solstice occurs when the Northern Hemisphere is tilted toward the Sun.
2. The winter solstice occurs when the Northern Hemisphere is tilted away from the Sun.
3. The spring equinox occurs when the Northern Hemisphere starts tilting slightly toward the Sun.
4. The fall equinox occurs when the Northern Hemisphere first starts to tilt away from the Sun.
III. Gravity, free-fall, and orbits
1. Gravity is a force that pulls a body towards the center of the Earth or towards two masses.
2. Gravity does not get weaker as a person pulls away from it; instead his or her body will become weightless.