The figure below shows the current measurements of the abundances of various light elements in the universe (vertical yellow bar), along with theoretical predictions. If you redetermined the abundance of ordinary helium (4He) and it was 90% of the current value, what would you conclude about the density of normal matter in today's universe?
A) It would be higher, and all the various density indicators would agree.
B) It would be higher, but the various density indicators would disagree.
C) It would be lower, but the various density indicators would disagree about its value.
D) It would be lower, but the various density indicators would agree.
E) It would be about the same as current observations suggest.

Question

The figure below shows the current measurements of the abundances of various light elements in the universe (vertical yellow bar), along with theoretical predictions. If you redetermined the abundance of ordinary helium (4He) and it was 90% of the current value, what would you conclude about the density of normal matter in today's universe? 
A) It would be higher, and all the various density indicators would agree. 
B) It would be higher, but the various density indicators would disagree. 
C) It would be lower, but the various density indicators would disagree about its value. 
D) It would be lower, but the various density indicators would agree. 
E) It would be about the same as current observations suggest.

Quizplus · Accepted Answer

The abundance of ordinary helium (4He) is a density indicator, and it depends on the density of protons and neutrons in the universe at the time of its production. If the abundance of helium was 90% of the current value, then the density of matter in the universe at that time would have been lower than the currently accepted value. However, the various density indicators (such as cosmic microwave background radiation and large-scale structure formation) would likely disagree about the exact value of the density, as they are sensitive to different aspects of the universe's evolution. Therefore, the correct answer is C.

The Figure Below Shows the Current Measurements of the Abundances