The Big Bang Theory

2. The simplest and most abundant element in the universe
4. The science that studies space, including stars, planets, galaxies, and everything beyond Earth's atmosphere
5. A scientist who discovered that the universe is expanding and showed that many galaxies exist outside our own Milky Way
10. A scientist who, along with Arno Penzias, discovered the cosmic microwave background radiation, helping confirm the Big Bang theory
13. The faint heat energy left over from the beginning of the universe, spread out evenly through space and detectable as microwave radiation
16. A huge group of stars, gas, dust, and planets held together by gravity
17. Light, colorless gas that doesn't react easily with other substances
18. A scientist who developed important ideas about space, time, and gravity, including the theory of relativity

1. A scientist who helped discover the cosmic microwave background radiation
3. A scientist who studied stars and helped develop ideas about how elements are made inside stars, and he also strongly disagreed with the Big Bang theory
6. The full range of all types of light energy, from radio waves to gamma rays, including visible light that humans can see
7. Everything that exists, including all space, stars, planets, galaxies, matter, and energy
8. Part of light that humans can see, made up of different colors ranging from red to violet
9. Idea that the universe began a very long time ago as a tiny, extremely hot and dense point
11. A tool that splits light into its different colors so scientists can study what something is made of and how it is moving
12. The ability to do work or cause change producing heat or creating light
14. When light from an object in space shifts toward the red end of the spectrum because the object is moving away from us
15. When light from an object shifts toward the blue end of the spectrum because the object is moving closer to us