Quiz 3: String Theory and Cosmology

. Check how much you've learned so far about the topics we've presented here with this self-scoring quiz.

Question 1: Why do astronomers and physicists believe the Universe is expanding?
The light from distant galaxies is is too hard to see.
The light from distant galaxies appears to Doppler-shifted.
The temperature of the Universe is getting cooler and cooler.

Question 2: Which observed feature of our visible Universe has not been explained through the Big Bang theory of cosmology?
The absence of isolated magnetic charge, known as magnetic monopoles
The temperature of the cosmic background radiation
Why there is so much more hydrogen than helium today

Question 3: How were the heavy elements like carbon and iron believed to have been made during the expansion of the Universe?
By confinement of quarks and gluons into baryons and mesons
By decoupling of matter and radiation
By nuclear fusion of light nuclei in the middle of stars, then ejection via supernova explosions

Question 4: In superstring theories, how many spacetime dimensions must remain tiny as the visible Universe expands?