The Big Bang

3. Prominent British astronomer and mathematician best known for explaining how chemical elements are created inside stars
7. A groundbreaking American astronomer who proved that other galaxies exist outside our own Milky Way
8. A massive, gravitationally bound system containing billions of stars, planets, gas, dust, and dark matter
9. The scientific study of everything in the universe outside Earth's atmosphere
12. German-born theoretical physicist widely considered one of the most influential scientists of all time
15. The narrow range of electromagnetic radiation (light) that the human eye can perceive, spanning colors from violet to red
16. An American astronomer who won the 1978 Nobel Prize in Physics for discovering cosmic microwave background radiation, which helped prove the Big Bang theory
17. An instrument that splits light into its different colors or wavelengths, creating a spectrum that is then recorded
18. The simplest, lightest, and most abundant chemical element in the universe

1. The "afterglow" or leftover heat from the Big Bang
2. A lightweight, colorless, and odorless gas that is commonly used to fill balloons and make them float
4. The capacity or ability to do work
5. American physicist who co-discovered Cosmic Microwave Background (CMB) radiation
6. The entire range of all possible frequencies of electromagnetic radiation, which travel in waves and transport energy
10. The leading explanation for how the universe began
11. Everything that exists, encompassing all space, time, matter, and energy
13. The displacement of the spectrum to shorter wavelengths in the light coming from distant celestial objects moving toward the observer
14. The stretching of light waves from an object (like a star or galaxy) as it moves away from the observer