Spaghettification Flip Book

PURPOSE:
The participants make a "Spaghettification Flip Book" to learn about the tidal forces due to gravity acting on different points of an object near a black hole.

OBJECTIVE:
• Students will be able to identify gravity as the main mover and shaper of the Universe.
• Students will articulate that a force is a push or pull on an object.
• Students will identify gravity as a force and will cite examples of gravity throughout the universe.
• Students will describe Newton's Laws using mathematical expressions and give examples that relate to everyday situations as well as locations near black holes.
• Students will manipulate the Universal Law of Gravitation and generalize that it depends upon the masses of two objects and the distance between them.
• Students will identify and describe black holes as extreme examples of gravity.
• Students will define black holes as (a) infinitely dense objects from which nothing, not even light can escape, and (b) massive objects that warp space and time.

INTENDED AUDIENCE:
9th - 12th grade

TIME REQUIRED:
45 Minutes

MATERIALS:
• Several pairs of scissors
• Several staplers
• Spaghettification Flip Book picture page
• Ruler
• Silly Putty (cut into human shapes with a cookie cutter if desired)

BACKGROUND INFORMATION:

Although so far no humans have come close enough to a black hole to experience its effects first hand, students are often fascinated by imagining what would happen if they ventured too close. Black holes are so massive that the forces due to gravity are many times stronger than they are here on Earth. Gravity is an attractive force that is responsible for the orbits of the planets, the fall of an apple from a tree, and our weight on the Earth's surface. The force due to gravity between two objects depends on three things: the masses of both objects and the distance between them. Newton's equation for gravitational force is F=GMm/R². On Earth, gravity acts differently on our feet than our heads. The reason for this is because the force of gravity is inversely related to distance. Our feet are closer to the center of the Earth than our heads (unless we were doing a handstand!). Since the force due to Gravity is not that strong, and the distance between our heads and our feet is not great, we hardly notice the difference in forces. This is not the case near black holes. Near black holes, the force of gravity is so strong that the pull is much stronger on the point closest to the black hole. If you went in feet first, the difference between the gravity acting on your head and your feet would be different enough to stretch you out end to end and compress you in the middle like a piece of spaghetti. The difference in the gravitational force near a black hole is so large that this effect would happen to just about anything that got too close.

This phenomenon is called "spaghettification" because the object approaching the black hole would be stretched long and thin like a piece of spaghetti. Unfortunately, humans could not survive this spaghettification process. Another, more general name for this effect is tidal force. A tidal force from a black hole is like the tidal forces of the Moon, which cause high and low tides in the oceans here on Earth. On the other hand, near a supermassive black hole, which is millions of times wider than other types of black holes, you would NOT be spaghettified before you reached the event horizon. The larger size of the supermassive black hole means that the tidal forces outside the event horizon are much weaker. However, you would still cross the event horizon of the black hole and not be able to escape. Likewise, the shorter a body is near a black hole, the less spaghettification will occur because there is less distance between the top and bottom of the body.

PREPARATION:
• Gather materials for all students.

PROCEDURE:
1. Ask students what would happen to their bodies if they were to venture too close to a black hole. Explain that this has not happened and is a purely imaginary trip.
2. Explain that black holes are so massive that the forces due to gravity are many times stronger than they are here on Earth.
3. Explain the factors that affect gravity. If appropriate, introduce Newton's equation for gravitational force, F=GMm/R².
4. Pass out 1 Spaghettification Flip Book Picture Page to each student.
5. Ask the students to imagine that the astronaut in the flip book page, is made up from many tiny little pieces (she or he is, after all, made from many cells, and the cells are made from atoms...).
6. Ask the students to measure the distance from a little piece at the bottom of the astronaut's foot to the bottom of the page (pretending that that is where the black hole is located).
7. Ask students to record that distance.
8. Then ask the students to do the same thing for a tiny piece near the astronaut's head.
9. Ask which distance is smaller (foot-black hole). Explain that the closer together the two objects are, the greater the gravitational force between them.
10. Ask the students to identify the area on the astronaut where the gravitational force is stronger (feet).
11. Have the students calculate the force of gravity for the two different distances.
12. Show students the silly putty astronaut. Ask what would happen if you pulled more strongly on the bottom of a piece of silly putty than on the top (the putty becomes stretched).
13. Explain that the difference in the gravitational force near a black hole is so large that this putty effect would happen to just about anything that got too close. Explain that this is called "spaghettification."
14. Relate what the students have just seen to tidal forces here on Earth.
15. Have students cut out each rectangle from the Spaghettification Flip Book Picture Page carefully.
16. Put square #1 on top. Put square #2 and all other squares below it, in order.
17. Staple through the top square on the small line.
18. Flip sheets from front to back.
19. Explain that, near black holes, the force of gravity is so strong that the pull is much stronger on the point closest to the black hole. Ask what would happen if the astronaut went in sideways. (The shorter a body is near a black hole, the less spaghettification will occur because there is less distance between the top and bottom of the body.)
20. Ask what would happen if the astronaut ventured near to a SuperMassive black hole. (In a supermassive black hole, which is millions of times wider than other types of black holes, you would NOT be spaghettified before you reached the event horizon. The larger size of the supermassive black hole means that the tidal forces outside the event horizon are much weaker. However, you would still cross the event horizon of the black hole and not be able to escape. )
21. (Optional) Have students complete the Spaghettification Worksheet found at the end of this lesson. The answer page can be found here.

EVALUATION:
• Have students apply the concepts above by asking them:
      - What might happen to a body other than a human (such as a car, or a planet) which was caught in the gravity of a non-supermassive black hole?
      - What would happen if you went in head first?
• Use your students' responses to the Spaghettification Worksheet to evaluate their understanding of tidal forces.