Question

Choose the correct statements from the following list. (Give ALL correct answers, i.e., B, AC, BCD...)

A) The critical density is the density needed to cause the Big Bang.

B) Assuming no dark energy, if the matter density of the universe is greater than critical, the universe is will eventually recollapse in a big crunch.

C) The horizon problem in cosmology is that regions of the universe that should not have ever had thermal contact with one another have the same temperature.

D) Assuming no dark energy, if the matter density of the universe is less than critical, the universe is closed.

E) A major difference between dark matter and dark energy is that one causes the universe's expansion to slow down, the other to make it expand faster.

F) Observations show us that the geometry of our universe must be very open

G) The inflationary model of the universe solves both the flatness and the horizon problems.

Answer 1

The answer will be BCEG, because in the first statement A critical density is the density that maintain the universe stability by not causing big bang expansion.

In statement B it is correct because as the matter density becomes more than the critical density the universe start contracting.

In statement C also in Horizon problem, they are not in contact with each other but they have a equal amount of temperatures everywhere as studied by CMB data

In statement D for if the matter energy density is less than critical density, the universe will be open and starts expanding continuously.

In statement E, it is right because the dark energy helps in expanding of the universe as it has repulsive forces and the dark matter help to contain the universe through its gravitational attraction.

In statement F, the universe shouldn't be open because open universe starts expanding and big bang occurs. Hence, the universe should be closed or should be flat.

In statement G, it is correct as the inflationary model actually solve the problem in some way.

I think this is the required answer. Hope you will like it. Thank you