Chelsea Esposito's Quiz

1. What do we mean by dark matter and dark energy?



Dark Matter is an undetected form of mass that emits little or no light but whose existence we infer from



its gravitational influence. Dark Energy is an unknown form of energy that seems to be the source of a



repulsive force causing the expansion of the universe to accelerate.



2. What is the evidence for dark matter in galaxies?



Rotation curves of galaxies are flat, indicating that most of their matter lies outside their visible regions.



3. What is the evidence for dark matter in clusters of galaxies?



Masses measured from galaxy motions, temperature of hot gas, and gravitational lensing all indicate that



the vast majority of matter in clusters is dark.



4. Does dark matter really exist?



Yes. Either dark matter exists or our understanding of our gravity must be revised.



5. What might dark matter be made of?



There does not seem to be enough normal (baryonic) matter to account for all the dark matter, so most



astronomers suspect that dark matter is made of (non-baryonic) particles that have not yet been discovered.



6. What is the role of dark matter in galaxy formation?



The gravity of dark matter seems to be what drew gas together into protogalactic clouds, initiating the



process of galaxy formation.



7. What are the largest structures in the universe?



Galaxies appear to be distributed in gigantic chains and sheets that surround great voids.



8. Will the universe continue expanding forever?



Current measurements indicate that there is not enough dark matter to prevent the universe from expanding



forever.



9. Is the expansion of the universe accelerating?



An accelerating universe is the best explanation for the distances we measure when using white dwarf



supernovae as standard candles.



10. Who discovered this acceleration?



Saul Perlmutter, Brian P. Schmidt, and Adam G. Riess for the 1998 discovery of the accelerating expansion



of the Universe through observations of distant supernovae.