Across
- 3. Downward movement under the force of gravity only.
- 5. A property of matter by which it continues in its existing state of rest or uniform motion in a straight line, unless that state is changed by an external force.
- 8. A person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft.
- 11. A natural satellite of any planet.
- 13. The chemical element of atomic number 2, an inert gas that is the lightest member of the noble gas series.
- 14. National Aeronautics and Space Administration
- 15. The science of the origin and development of the universe.
- 16. A region of space-time exhibiting such strong gravitational effects that nothing—not even particles and electromagnetic radiation such as light—can escape from inside it.
- 19. The leading explanation about how the universe began.
- 20. To orbit a central point.
Down
- 1. The brightest star in the constellation of Cygnus.
- 2. The great size or extent of something.
- 4. Space void of matter.
- 6. A thin band or disk of rock and ice particles around a planet
- 7. The universe seen as a well-ordered whole.
- 9. The lowest possible temperature (-273.16°C).
- 10. The center of gravity of the Earth and moon.
- 12. A gravitationally curved path of an object about a point in space.
- 17. An imaginary line on which objects rotate on.
- 18. A period of twenty-four hours as a unit of time (on earth).