Self-study
Astronomer: Earlier estimates of the distances of certain stars from Earth would mean that these stars are about 1 billion years older than the universe itself, an impossible scenario. ██ █████████ ██ ███ █████████ ████████ ████ █████ █████ ███ ████ ███████ ████ ████ ██████████ ████████ ███ ███ ███████ ████ ███ █████ ████ ███ ███████ █████ █████████ ██████████ ████ ███ █████ █████ ██████████ ██ ██ ██ ██████ ██ ███ ███ █████████ ██ █████ ██████ █████████ ████ █████ ████ ███████ ███ ███████ ████████ ███████ ███ ████ ██ █████ █████ ███ ███ ███ ██ ███ █████████
"Surprising" Phenomenon
Why does knowing these stars are farther from Earth resolve the discrepancy between their age and the age of the universe?
Objective
Any hypothesis explaining why this conflict is resolved must imply that the stars are younger than previously estimated or that the universe is older than previously estimated. Correcting the distances of these stars from Earth was enough to resolve the conflict, so the correct answer must imply that more distant stars imply an older universe or that knowing stars are more distant allows scientists to know they are younger.
20.
Which one of the following, ██ █████ ████ █████ ██ ███████ ███ ███ ████████████ █████████ ██ ███ ██████ █████████ ████ █████ ████ ███████ ███ ███████ ████████ ███████ ███ ████ ██ █████ █████ ███ ███ ███ ██ ███ █████████
a
The stars are ███ ██████ ███████ ███ ██████████ ██ ███ █████████
This does not state that the universe is older than previously estimated, nor does it provide a reason for concluding so. It remains unexplained why updating the stars’ distances resolves the apparent conflict between the age of the stars and the age of the universe.
b
The younger the ████████ ███ ███ ████ ██████ █████ ██ ██ ██████ ██ █████
This makes the resolution more surprising. Since the stars are more distant, they have a greater inherent brightness to achieve the same apparent brightness here on Earth. Therefore, this suggests the universe should be younger than previously estimated, not older.
c
The brighter a ████ ███ ███ ███████ ██ ███
This explains why correcting the stars’ distances resolves the conflict. If the stars are more distant than believed, they must have a greater intrinsic brightness to achieve the same apparent brightness. This means they are younger than the earlier estimates suggest.
d
How bright celestial ███████ ██████ ██ ██ ███████ ██ ███ ███ ████ ████ ███ ████████ ████ ████
This is not enough information to explain why the conflict is resolved. It is a generalization of the astronomer’s claim that farther stars must have a greater intrinsic brightness to achieve the same apparent brightness on Earth.
e
New telescopes allow ███████████ ██ ███ █ ███████ ██████ ██ ███████ ██████
This is irrelevant information. Improved telescopes may explain how the stars’ distances were corrected, but not how that correction resolves the conflict regarding their age.