1. Bellwork True or False: 1. Mirrors are used in some telescopes.
2. Telescopes are often located in humid environments because water vapor in the air enhances visibility of stars.

2. Bellwork
List the planets in order by the time it takes to orbit the sun from fastest to slowest.
If the semimajor axis of Earth’s orbit is 150 million Km, what is the major axis? (use pg. 81 for help)
What 2 properties affect the force of gravity?

3. Astronomy
Bellwork
What is astronomy?
Objective: Students will describe the difference between rotation and revolution in written notes.

4. Astronomy is…
the study of the universe to include moons, planets, stars, and other objects in space

5. Beginnings of Astronomy

6. Have you ever asked yourself?
This man has the answers
Why do the planets revolve around the sun?
Why don’t they fly off into space?
Does something hold them in their paths?

7. Can you distinguish the difference between rotation and revolution?

8. Difference between rotation and revolution.
When an object in space spins on it’s axis
Earth’s rotation on it’s axis causes day and night
Revolution
The movement of one object around another
Earth’s revolution around the sun is called a year.

9. Earth – about every 24 hours
Time Measurements
DAY (rotation)
– time it takes for a planet to rotate once around its own axis.
Earth – about every 24 hours
(23 hrs 56 min)
YEAR (revolution)
– time it takes for a planet to orbit once around the sun.
Sun
EPlanet
Earth – every days

10. Why is there an extra day in February every fourth year?
Earth’s orbit takes 365 ¼ days. To account for the ¼ day we add an extra day every fourth year. We call that year leap year.

11. Why do we have seasons?
Earth has seasons because its axis it tilted as it moves around the sun.

12. Seasons
– The tilt of the Earth’s axis causes the northern & southern hemispheres to get different amounts of solar radiation causing the different weather.

13. Solstice and Equinox Solstice Equinox
Two days of the year where the noon sun is overhead at either 23.5 degrees south or 23.5 degrees north.
Equinox
Two days of the year where neither hemisphere is tilted toward or away from the sun
Equinox means “equal night”

14. Sep 21, 2005
Dec 20, 2005
Mar 20, 2006
Jun 21, 2006
Sep 23, 2006
The amount of sunlight hitting different parts of the Earth changes as the Earth moves around the Sun over a year.

15. the one day of the year when the sunlight time is longest.
Sep 21, 2005
Dec 20, 2005
Mar 20, 2006
Jun 21, 2006
Sep 23, 2006
Summer SOLSTICE
the one day of the year when the sunlight time is longest.

16. the one day of the year when the sunlight time is shortest.
Sep 21, 2005
Dec 20, 2005
Mar 20, 2006
Jun 21, 2006
Sep 23, 2006
Winter SOLSTICE
the one day of the year when the sunlight time is shortest.

17. Sep 21, 2005
Dec 20, 2005
Mar 20, 2006
Jun 21, 2006
Sep 23, 2006
Spring EQUINOX
the one day between winter and summer when the sunlight time and night time are of equal length.

18. Sep 21, 2005
Dec 20, 2005
Mar 20, 2006
Jun 21, 2006
Sep 23, 2006
Autumn EQUINOX
the one day between summer and winter when the sunlight time and night time are of equal length.

19. Chapter 1 Section 1 Review
Why does Earth have day and night?
Why does Earth have seasons?
What is the difference between rotation and revolution?
What is leap year?

20. What is an astronomical unit?
AU – the distance from the earth to the sun. Approx. 150 million kilometers

21. Kepler’s 3 Laws

22. Kepler’s laws of motion?
The first law states that orbits are elliptical.
An ellipse is a closed curve in which the sum of the distances from the edge of the curve to two points inside the ellipse is always the same.
What are
Kepler’s laws of motion?

24. Kepler’s laws of motion?
The second says that planets move faster when they are closer to the sun and slower the farther away they are.
Mercury, the innermost planet, takes only 88 days to orbit the Sun but the outermost planet (Pluto) requires 248 years to do the same
What are
Kepler’s laws of motion?

26. Kepler’s laws of motion?
The third explains the relationship between the period of revolution and the semimajor axis of the elliptical orbit.
Planets further from the sun, such as Saturn, take longer to orbit the sun.
What are
Kepler’s laws of motion?

29. -Newton explained that the force of gravity on an object in the solar system depends on its mass and distance from the sun.
-This force along with the forward motion of the object keeps it in an elliptical orbit around the sun.
How does the
Law of Universal
Gravitation explain
how the objects in the
solar system revolve
around the Sun?

31. Newton’s law of universal gravitation- The force of gravity depends on the product of the masses of the object divided by the square of the distance between the objects.

32. Bellwork
List the planets in order by the time it takes to orbit the sun from fastest to slowest.
If the semimajor axis of Earth’s orbit is 150 million Km, what is the major axis? (use pg. 81 for help)

33. Bellwork
List the planets in order by the time it takes to orbit the sun from fastest to slowest.
If the semimajor axis of Earth’s orbit is 150 million Km, what is the major axis? (use pg. 81 for help)
What 2 properties affect the force of gravity?