Which of the following statements correctly describes the "flatness problem" in cosmology?
A)Observations of the distant universe indicate that the universe is at least moderately flat, yet matter creates lumps in the geometry of spacetime. Therefore it is hard to account for the observed flatness.
B)The density of the universe must have been equal to the critical density to a precision of 50 decimal places in order for us to see the universe we see today. This astounding flatness is hard to account for.
C)The universe appears to have a hyperbolic geometry to within observational error, yet the universe is expanding, and expanding universes have to be flat.
D)The universe appears to be flat to within observational error, yet the universe is expanding, and it is impossible for an expanding universe to be flat.

Question

Quizplus · Accepted Answer

The flatness problem refers to the mystery of why the density of the universe is so close to critical density, to a precision of about 50 decimal places. If the density had deviated from the critical value by more than a tiny fraction, the universe would be severely curved, and this would have had important consequences for the evolution of the universe, such as the way in which galaxies form. It is hard to account for this apparent fine-tuning of the initial conditions of the universe.

Which of the Following Statements Correctly Describes the "Flatness Problem