In the early universe, why were inhomogeneities in the distribution of normal matter much smaller than inhomogeneities in the dark matter?
A) Normal matter was pushed away by supernova explosions.
B) Large-scale magnetic fields smoothed the distribution of charged particles in the normal matter but not in dark matter.
C) Dark matter particles were more massive than and cooled off before normal matter, and so dark matter fluctuations had more time to grow.
D) Dark matter was 10 times more massive than normal matter.
E) Radiation pressure affected normal matter but not dark matter.

Question

Quizplus · Accepted Answer

Radiation pressure from photons in the early universe smoothed out fluctuations in normal matter, which interacts with radiation, while dark matter does not interact with radiation and thus retained its inhomogeneities.

In the Early Universe, Why Were Inhomogeneities in the Distribution