Download How does the earth orbit the sun?

Earth’s Motions
Bellwork page: ______
How does the earth orbit the
sun?
4
Aphelion: point in the earth’s orbit where the earth and sun are the furthest
apart.
Ellipse: oval-shaped
Gravity: force of attraction that exists between all objects in the universe
Perihelion: point in the earth’s orbit where the earth and sun are the closest.
January 3
July 4
94,500,000 miles
91,500,000 miles
Look at the figure above. Notice that the earth’s orbit is not in the shape of a circle.
The earth’s orbit is slightly oval-shaped. This
shape is called an ellipse.
What is the difference between a circle and an
ellipse?
In a circle, the distance from the center to any
point along the edge is the same. In an ellipse,
the distance from the center to the edge changes
as you move along the edge. An ellipse has a long axis and a short axis. They cross at
right angles at the center of the ellipse.
The earth’s orbit is an ellipse. The sun is not exactly in the center of the ellipse. It is
slightly off center. For these reasons, the earth is not the same distance from the sun at
all times.
Around January 3, the earth is closest to the sun. It is about 147 million kilometers
away. The point in the orbit that is closest to the sun is called the perihelion.
Around July 4, the earth is farthest from the sun. It is about 152 million kilometers
away. The point in the orbit that is farthest away from the sun is called the aphelion.
All the planets-not just the earth-orbit the sun in elliptical paths.
1. What is the shape of the earth’s orbit? ____________________
2. Is the sun in the center of the orbit?
____________________
3. Is the earth the same distance from the sun along the entire orbit? ___________
4. How far is the earth from the sun around January 3? _________________
5. On January 3 the earth is the ______________ from the sun.
6. What do we call this point in the earth’s orbit?
___________________________
7. How far is the earth from the sun around July 4? _________________________
8. On July 4 the earth is the ______________ distance from the sun.
9. What do we call this point in the earth’s orbit? __________________________
A planet moves at different speeds at different points of its orbit. The speed depends upon
how close or far away from the sun the planet is.
10. How many planets orbit the sun? (if you were to include Pluto) ________
11. List the planets in order starting with the planet that is closest to the sun.
1. _________________
6._________________
2. _________________
7._________________
3. _________________
8. _________________
4. _________________
9.__________________
5. _________________
12. What shape is the orbit of EVERY planet? ________________
Scientists have found that the CLOSER a planet is to the sun, the FASTER it moves.
The FARTHER a planet is from the sun, the SLOWER it moves. The speed of a
planet’s orbit is called it’s orbital velocity.
13. Which planet has the slowest orbital velocity? _________________
14. Why does this planet have the slowest orbital velocity?
______________________________________________________________
15. Which planet has the fastest orbital velocity? ____________________
16. Why does this planet have the fastest orbital velocity?
______________________________________________________________
A planet moves at different speeds at different points of its orbit. The speed
depends upon how close or far away from the sun the planet is.
17. On which date does the earth move the fastest? _____________________
18. Why does it move the fastest on this date?
______________________________________________________________
19. On which date does the earth move the slowest? _________________________
20. Why does it move the slowest on this date?
______________________________________________________________
You throw a ball into the air. It moves upward for a short time. Then it starts falling back to the
ground. Why does it fall back? Why doesn’t it keep moving upward? A force called gravity pulls
it back toward the earth. Gravity is a pulling force. It is the force that attracts objects toward one
another.
Gravity pulls the earth and anything on the earth towards one another. As you stand on the
earth, you are pulled downward, towards the center of the earth.
Every object in the universe pulls on every other object in the universe, from the tiniest atom to
the largest star. However, all objects do not have the same gravitational pull. The strength of a
gravitational pull depends upon two things. They are the amount of matter something has
(mass) and the distance.
Amount of matter is the objects pulling on each other. The more matter there is the stronger the
pull. The pull of an atom is tiny. The pull of the star is huge.
Distance between the objects is also important. The closer two objects are to each other, the
more they pull on each other. The pull of earth on you is very large since you are so close to
the earth. The pull on Jupiter on you is smaller since Jupiter is so far away.
Gravity holds the planets around the sun and moons around the planets. If there were no gravity
the planets would just fly off into space away from the sun.
Complete each statement using the words below.
Matter
Gravity
Moon
Distance between
Downward
pulling
Sun
21. The force that pulls objects toward one another is called _______________.
22. Gravity is a ____________ force.
23. Gravity pulls things on the earth ______________.
24. Gravity depends upon two things; the amount of ____________ objects have, and
the _______________________________ the objects.
25. Gravity keeps the ____________________ moving around the earth. It also
keeps the planets moving around the _______________________.
In the spaces provided write “True” if the sentence is true. Write “False” if the
sentence is false.
26. _________ The planets move in circular orbits around the sun.
27. _________ The sun is in the very center of the earth’s orbit.
28. _________ The earth is the same distance from the sun at all times.
29. _________ The earth’s orbital velocity changes as it moves around the sun.
30. _________ Aphelion is the closest point of an orbit.
31. _________ Perihelion is the closest point of an orbit.
32. _________ The earth is at aphelion in July.
33. _________ The earth is closest to the sun in July.
34. __________ The closer a planet is to the sun, the faster it moves.
35. _________ The orbital velocity of Pluto is faster than the orbital velocity of
earth.