How did Hubble tell the universe was expanding?

Related questions

1. What is light distortion?
2. What causes atmospheric blurring?
3. What is lens distortion correction?
4. How long would it take to travel 4 light years?
5. How do you see Neptune?
6. What is the hottest and coldest star?
7. What causes atmospheric turbulence?
8. Which is closer to Earth moon or stars?
9. What's the coldest star in the universe?
10. What is the hottest planet in the universe?

Tags

1. #earth
2. #galaxy
3. #finding
4. #distance
5. #universe
6. #proportional
7. #expanding
8. #brilliant
9. #farther
10. #faster
11. #moving
12. #things
13. #hubble
14. #meant
15. #announced
16. #directly
17. #other
18. #observation
19. #shift
20. #words
21. #galaxies