1. WARM UP/ DO NOW
1) Where does nuclear fusion occur and where does nuclear fission happen?
2) Explain the Doppler Effect
3) What is Hubble’s Law and what theory does it explain?

2. Early Astronomy Astronomy: Study of the universe
The Greeks made many astronomical discoveries.

3. Varying Models
Geocentric (Earth centered): Moon, Sun and the planets orbit the Earth.
Heliocentric (sun centered): Earth, the Moon and the other planets orbit the Sun.

6. Laws of Planetary Motion
Kepler: Used math to discover 3 laws of planetary motion.
The path of each
planet around the sun
is an ellipse.

8. Kepler’s 2nd Law
2. Each planet revolves so that an imaginary line connecting it to the Sun sweeps over equal areas in equal time intervals.
-This means that planets travel faster when they are closer to the Sun and slower when they are farther away.

10. Kepler’s 3rd Law
The length of time that it takes a planet to orbit the Sun and it’s distance to the Sun are proportional.
The farther away, the longer it takes to orbit

12. Rotation of Earth
Rotation: The turning or spinning of a body on it’s axis.
Earth’s rotation is what is responsible for day and night.
1 rotation= 1 day

14. Revolution of Earth
Revolution: The motion of a body along a path around some point in space
Earth revolves around the Sun and the Moon revolves around Earth.
1 revolution= 1 year ( days)

15. Earth’s Position
Aphelion -- the point on its orbit when the Earth is farthest from the sun
Perihelion -- the point on its orbit when the Earth is closest to the sun
(FYI: Helion=nucleus of a helium-3 atom)

17. Seasons Seasons occur as a result of Earth’s tilt.
Earth’s axis is tilted 23.5 degrees
Because of this, the sun hits at difference angles, causing different seasons in different hemispheres.

19. Northern Hemisphere Seasons
Equinox: Equal day and equal night. Happens when the sun crosses directly over the equator.
Spring Equinox=March 21st or 22nd (Earth is North of the Sun)
Autumnal Equinox=September 22nd or 23rd (Earth is South of the Sun)

20. Equinox

21. Northern Hemisphere Seasons
June 21st or 22nd=Summer Solstice -longest day of summer (Sun’s angle and Earth’s tilt create larger amounts of daylight)
December 21st or 22nd=Winter Solstice-shortest day of the year (Sun’s angle creates and Earth’s tilt create less daylight)

22. Summer Solstice

23. Winter Solstice

24. Precession and Nutation
Earth’s axis maintains
same angle of tilt
DIRECTION the axis
points constantly changes
Nutation
Wobble around the
axis

25. Effects of Precession and Nutation
Changes position of stars and constellations relative to someone on Earth.
Currently, axis points toward Polaris (North Star)
Year 14,000: axis will point toward Vega
Period of precession is 26,000 years
By the year 28,000, axis will point to Polaris again.

26. Barycenter
The point between two objects where they balance each other.
the center of mass where two or more celestial bodies orbit each other.
When a moon orbits a planet, or a planet orbits a star, both bodies are actually orbiting around a point that is not at the center of the primary (the larger) body.

28. Earth’s Moon
Giant Impact Hypothesis: Most widely accepted model for the formation of the moon.
States that when the solar system was forming, a body the size of Mars impacted the Earth. A piece of the debris got ejected into Earth’s orbit and became the moon

30. Earth’s Moon Perigee: When the moon is closest to Earth
Apogee: Moon is farthest from Earth
Lunar phases are a result of the motion of the moon and the sunlight that is reflected from its surface