Laniakea, our Supercluster, is 500 million light years wide

http://apod.nasa.gov/apod/ap140910.html

Our universe is a simple place. The distribution of matter is pretty much the same everywhere (on sufficiently large scales).

What is redshift?

What is dark matter?

Even around a galaxy, dark matter dominates

Evidence for Dark Matter: 1. Stellar Rotation in galaxies

One way to “weigh” things in the universe:

Gravitational lensing.

The gravitational field of a galaxy (or cluster of galaxies) deflects passing light; the more mass, the greater deflection.

So we can infer the existence of matter even if we can't see it.

Bullet Cluster

Bullet Cluster

Bullet Cluster

Evidence for Dark Matter: 2. Galaxy collisions

http://apod.nasa.gov/apod/ap060824.html

What is dark matter?

Hypothetical form of matter … but evidence that it exists!

Interacts with gravity

Does not interact with light (electromagnetic radiation)

cold, warm, and hot dark matter. Cold favored.

How did we detect neutrinos?

Sudbury Neutrino Observatory, 12-m sphere2000 m undergroundOntario, Canada

Kamiokande Detector50,000 tons of ultra-pure water1000 m undergroundMt. Kamioka, Japan

Detect dark matter? Let’s go 8000 ft below ground level at < 100 mK

What is dark energy?

But don't get complacent: the universe is expanding.

1929: Edwin Hubble shows that the further away a galaxy is, the more rapidly it is moving away from us.

Modern version of Hubble's diagram.

v = H0d, where the slope H0 is the "Hubble constant".

What does "expanding" mean? Distant galaxies are receding; the more distant, the faster the recession. Nothing more or less than that!

size

t> Big Bang <

Why need dark energy?

Universe is expanding!

Universe is flat!

Universe has large scale wave-patterns of mass density

How fast are supernovae moving away from us?

SN Ia

Brig

htne

ss

Redshift

dist

ance

dist

ance

Nobel Prize (1998): Universe is expanding!

Density of Matter

Den

sity

of E

nerg

y