How did Edwin Hubble measure the distance to the Andromeda Galaxy?
A) He measured its parallax.
B) He applied the period-luminosity relation to Cepheid variables.
C) He deduced it from its redshift.
D) He used white dwarf supernovae.
Question 2
What use are 21 cm radio waves to Galactic astronomers?
A) They cut through the dusty cocoons to let us watch star birth.
B) We can reflect them off the core of the Galaxy.
C) Their Doppler shifts let us map the motions and locations of gas in the spiral arms.
D) They bounce off stars like our Sun to let us precisely measure their distances.
E) They pick up the cool, dark matter much better than can optical telescopes.
Species richness decreases with distance from the source pool.
Scale used to measure pupil size in millimeters.
Uranus revolves around the Sun once every 84 Earth years. Its average distance from the Sun is rough
The Reinstatement Procedure, a Measure of Craving
A partial stream sampling exhaust probe being used to measure exhaust gases in parts per million ...
Fornax Galaxy Cluster