Author Question: The period-luminosity relation for Cepheid variables was discovered in 1908 by A) William ... (Read 86 times)

jhjkgdfhk · **on:** Jul 27, 2018

The period-luminosity relation for Cepheid variables was discovered in 1908 by

A) William Herschel.
B) Henrietta Leavitt.
C) Harlow Shapley.
D) Heber Curtiss.
E) Edwin Hubble.

Question 2

Hubble's constant is related to the age of the universe, but the precise relationship depends on the way in which the expansion rate changes with time.

For a given value of Hubble's constant today (such as 24 km/s/Mly), the age of the universe is oldest if what is true? A) The expansion rate has remained nearly constant with time (a coasting universe).
B) The expansion rate has slowed by the amount expected for a universe with the critical density (a critical universe).
C) The expansion rate has been increasing with time (an accelerating universe).
D) The expansion rate is slowing dramatically with time (a recollapsing universe).