Prof Martin HendryUniversity of Glasgow

A long time ago,

in a galaxy far, far away…

The nature of the nebulae?…

Early 20th Century

Gas clouds within the Milky Way, or Island Universes?….

Galaxy

Laboratory

Hubble’s Law

Einstein’s RelativityEinstein’s Relativity

Matter causes space Matter causes space to to curvecurve or or warpwarp

“Space tells matter how to move, and matter tells space

how to curve”

Gravity in Einstein’s Universe

Will the Universe expand forever?...

It depends how much matter there is

Weighing the Solar System

Johannes Kepler

Isaac Newton

Vera Rubin

1970s: studies the rotation of

spiral galaxies.

Weighing galaxies

Galaxies were spinning faster than they should be!

What we seeWhat we see

What we think is really there….

10 times as much as the luminous matter in the visible galaxy

Will the Universe expand forever?

Answer depends on the density of matter in the Universe.

Density high enough to cause re-collapse, leading to ‘Big Crunch’

Density too low; Universe expands forever

‘Critical’ density

So, is the expansion slowing down?...

Answer depends on the shape of the Universe

Answer depends on the shape of the Universe

Closed

Answer depends on the shape of the Universe

Closed Open

Answer depends on the shape of the Universe

Closed Open Flat

redshift

‘Speeding up’ model

‘Slowing down’ model

Hubble’s law for nearby supernovae

Hubble diagram of distant supernovaem

easu

re o

f di

stan

ce

So what exactly is this dark energy?...

So what exactly is this dark energy?...

redshift

Latest results: still speeding up...m

easu

re o

f di

stan

ce

Early Universe too hot for neutral atoms to exist

Free electrons scatter light (as in a fog)

Early Universe too hot for neutral atoms to exist

Free electrons scatter light (as in a fog)

After ~380,000 years, Universe cool enough for neutral hydrogen to form: the fog clears!

Background radiation predicted in 1950s and 1960s by Gamov, Dicke, Peebles.

Discovered in 1965 by Penzias and Wilson

Arno Penzias and Robert Wilson

Robert Dicke

Jim Peebles

COBE map of temperature across the sky

CMBR ‘ripples’ are the seeds of today’s galaxies

Galaxy formation is highly sensitive to the pattern of CMBR temperature

WMAP map of temperature across the sky

Adapted from Bassett & Nichol (2006)

Coming attractions...

Coming attractions...• Multi-wavelength (messenger)

• Ground- and space-based

• Multiple cosmological probes:

• Many opportunities for better constraining dark matter and dark energy models

Supernovae Gamma-ray bursts GW ‘Sirens’ Baryon Acoustic Oscillations Galaxy Cluster Statistics Weak Gravitational Lensing

???