1. WHAT IS…..
DARK MATTER??

2. What do you call something you can’t see?
OR…
What do you call something you can’t see?

3. It is estimated that
only 10% of the matter in the universe is emitting electromagnetic radiation. AND

4. 1% of the total matter in the universe.
Perhaps only
1% of the total matter in the universe.

5. Why suggest there is more matter?
The force that causes motion in the universe is GRAVITY.
Gravity depends on the mass of the objects doing the pulling, and the distance between them.

6. So….
objects farther from the gravitational center should move more slowly in their orbits.

7. P2 = a3 Kepler’s 3rd Law: p = period of revolution
a = distance from other body
(see Kepler’s laws simulator under websites)

8. The center of the Milky Way has most of the mass.
Q: So why don’t the stars on the outside of the galaxy revolve around the center more slowly than those near the center??????

9. A: There must be
Matter (unseen) closer to those outer stars must be pulling them along, adding to their orbital speed.