If neutrinos have mass but do not interact much with normal matter,why can't they be the dominant form of dark matter in the universe?
A) Structure formation would have started with large objects fragmenting into smaller objects.
B) Structure formation would have started with small objects merging to form larger objects.
C) Neutrinos would decay over time and disappear,causing galaxies to fall apart.
D) Neutrinos would not gravitationally lens background galaxies.

Question

Quizplus · Accepted Answer

Neutrinos have a high velocity and low mass, meaning they would have been moving too fast to clump together via gravity and form the large structures we observe in the universe. Therefore, structure formation would have started with large objects fragmenting into smaller objects, which is inconsistent with the observed formation of galaxies and large scale structures.

If Neutrinos Have Mass but Do Not Interact Much with Normal