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 Relationship Surface Area ~ r 2 Brightness ~ 1/r 2
Mass of H: Mass of He: 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!
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 2008Richardson-McDaniel22 What is Gravitational Lensing?
15 February 2008Richardson-McDaniel23 Strong Lensing Effects Einstein Ring Multiple Images, Arcs
15 February 2008Richardson-McDaniel24
What is Dark Matter?
Summary 1) 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 velocities 3) Dark matter is not ordinary matter -We understand gas dynamics -We can use gravitational lensing to measure mass