1. how did astronomers confirm the existence of dark energy?
a. by calculating it using kepler’s third law
b. by measuring the mass of galaxies
c. by detecting it with telescopes
d. by the ages of globular clusters

2. how did astronomers confirm the existence of dark matter?
a. by measuring how fast the universe is expanding
b. by detecting very hot gas in galaxy clusters that emits x-rays
c. by measuring the amount of compressed gas in the universe
d. by detecting electromagnetic radiation reflecting from the dark matter