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.
"Visual Acuity Testing, Assessing Distance Vision
Using a sphygmomanometer to measure blood pressure.
Major moons of Uranus in order of increasing distance (left to right), at their proper relative size
Elliptical Galaxy M32
Wintrobe tube and Westergren tests are used to measure the ESR.
A hydrometer is used to measure the American Petroleum Institute (API) specific gravity of diesel ...