The theory of relativity usually encompasses two interrelated theories by Albert Einstein: special relativity and general relativity. Special relativity applies to elementary particles and their interactions, describing all their physical phenomena except gravity. General relativity explains the law of gravitation and its relation to other forces of nature. It applies to the cosmological and astrophysical realm, including astronomy.

The theory transformed theoretical physics and astronomy during the 20th century, superseding a 200-year-old theory of mechanics created primarily by Isaac Newton. It introduced concepts including spacetime as a unified entity of space and time, relativity of simultaneity, kinematic and gravitational time dilation, and length contraction. In the field of physics, relativity improved the science of elementary particles and their fundamental interactions, along with ushering in the nuclear age. With relativity, cosmology and astrophysics predicted extraordinary astronomical phenomena such as neutron stars, black holes, and gravitational waves.

Albert Einstein published the theory of special relativity in 1905, building on many theoretical results and empirical findings obtained by Albert A. Michelson, Hendrik Lorentz, Henri Poincare and others. Max Planck, Hermann Minkowski and others did subsequent work.

Einstein developed general relativity between 1907 and 1915, with contributions by many others after 1915. The final form of general relativity was published in 1916.

1. Whose theory did Einstein's replace?
2. How old was Newton's theory?
3. What is one phenomenon predicted with relativity in the field of astronomy?
4. Did the theory predict black holes?
5. Neutron stars?
6. Supernovae?
7. Was Einstein's theory based entirely on his own findings?
8. What is the name of one man whose findings Einstein drew from?
9. And another?
10. And one more?
11. Did Max Planck continue in Einstein's line of work?
12. Who else did?
13. What age did Einstein's theories bring about?
14. What two theories are included in the theory of relativity?
15. True or False: Special relativity describes how gravity works.
16. Does general relativity apply to the study of space?
17. What century does Einstein's theory belong to?
18. In what year did he begin to develop general relativity?
19. When did he publish its final form?
20. When did others begin to add to it?
1. Isaac Newton
2. 200
3. cosmological
4. yes
5. yes
6. no
7. no
8. Albert A. Michelson
9. Hendrik Lorentz
10. Henri Poincare
11. yes
12. Hermann Minkowsk
13. nuclear age
14. special relativity and general relativity
15. false
16. yes
17. 20th century
18. 1907
19. 1916
20. 1915