In the very first phase after the big bang, when the Universe was about a microsecond old, space was filled with____.
a. high-energy photons
b. protons and antiprotons
c. protons, neutrons, electrons, and positrons (anti-electrons)
d. electrons, and positrons (anti-electrons)
e. protons, neutrons, electrons
Question 2
When mapping the interior of the Sun, astronomers must measure _____ as the photosphere moves up and down.
a. Doppler shifts
b. magnetic fields
c. sunspots
d. limb darkening
e. supergranules