11 - Dark Matter in Cosmology

Radiation has a ____ pressure compared to the pressure from the number of atoms in deep space.

high

Pressure ___________ gravity and stops light from _________ under its own pull

Counteracts, collapsing

The _____ and ordinary matter will interact - ______ bounce off atoms, and atoms off atoms.

Light, photons

What will ignore both photons and baryons?

Dark matter

Light and atoms both do not ______, so only ____ ______ is pulled into clumps by _______.

Cluster, dark matter, gravity

___ provides a hyper-precise and very well-understood measurement that cannot be fit without dark matter.

CMB

There is about _ times as much dark as regular matter.

5

The CMB fluctuations are the seeds of modern-day _______.

Galaxies

What is the primary blob size in the CMB called in galaxies (initially generated from sound pressure waves in the early universe)?

BAO peak (Baryon Acoustic Oscillations)

Gravity bends _____, but not very much due to its speed (need massive source of gravity to bend it enough to be able to detect).

Light

The first lensing measurement by Arthur ___________ during solar eclipse ____.

Eddington, 1919

Why is lensing evidence for dark matter?

Lensing shows how mass influences the path of light, revealing the presence of unseen mass, such as dark matter, based on the amount of bending observed compared to the visible matter.

What are “arcs”?

Background galaxies lensed around cluster mass

Galaxy clusters in X-ray are dominated by ___.

Gas

Dark matter does not _______; particles move straight through each other.

Collide

We can measure ____ _______ across the whole sky, and measure the average DM density across the Universe.

Weak lensing