How did the universe begin?

How do we know?Doppler Shift

Lower pitched,longer wavelength

Higher pitched,shorter wavelength

Longer wavelength-->

Shorter wavelength-->

Redshift & Velocity

Distance & Brightness RelationshipSurface Area ~ r2

Brightness ~ 1/r2

Mass of H: 1.0079

Mass of He: 4.0026

How stars burn: 4H → 2He

Super Novae are standard candles

Hubble's Law

1) The universe is expanding (Hubble's Law)

- We can measure galaxy redshifts (velocities)-We know about spectral absorption lines.

-We understand how these lines are redshifted. - We can measure luminosity (brightness) - We can connect luminosity to distance (Super Novae)

Evidence for Dark Matter

How fast do you have to travel to leave the Earth?

Fun with cannons!http://galileoandeinstein.physics.virginia.edu/more_stuff/Applets/newt/newtmtn.html

How fast do you have to travel to leave the Earth?

Kinetic (moving) Energy Potential

Energy (height)

Energy Conservation

How fast do you have to travel to leave the Earth?

Kinetic (moving) Energy Potential

Energy (height)

Energy Conservation

7 miles/s

Binary Stars

Dark Matter Rotation Curve

2) There is more mass in galaxies than can be explained by starlight alone (Dark Matter) -We know the star-mass in galaxies because we can measure binary star system masses and luminosities -We know how fast galaxies are moving -We know the required mass because we understand escape velocities

The Bullet Cluster

Gas Dynamics

15 February 2008 Richardson-McDaniel 22

What is Gravitational Lensing?

15 February 2008 Richardson-McDaniel 23

Strong Lensing EffectsEinstein RingMultiple Images, Arcs

15 February 2008 Richardson-McDaniel 24

What is Dark Matter?

Summary1) The universe is expanding (Hubble's Law)

- We can measure galaxy redshifts (velocities) - We can measure luminosity (brightness) - We can connect luminosity to distance (Super Novae)2) There is more mass in galaxies than can be explained by starlight alone (Dark Matter) -We know the star-mass in galaxies because we can measure binary star system masses and luminosities -We know how fast galaxies are moving -We know the required mass because we understand escape velocities3) Dark matter is not ordinary matter

-We understand gas dynamics -We can use gravitational lensing to measure mass