Across
- 2. growing
- 3. electromagnetic radiation
- 6. person who helped others understand gravity
- 7. a force
- 8. a particle of matter
- 9. an idea
Down
- 1. the universe expanding
- 2. radiation and their respective wavelengths and photon energies
- 4. any substance that has mass and takes up space by having volume
- 5. space