The Universe

Known Universe

Our Neighboring Galaxies-Visible Light

Doppler effect & Red Shift Edwin Hubble, 1929 Realized that dimmer galaxies are likely farther away. The farther the galaxy, the greater the red shift. –Red shift = when a light source is moving away from the observer, the light waves get “stretched” causing it to appear redder than it really is. (Doppler effect)

Red Shift Top = Red shift: object moving away Middle = No shift: object not moving toward or away Bottom = Blue shift: object moving toward

Doppler Animation plershift.html

Hubble ’ s Law The Doppler effect can be used to figure out not only if an object is moving toward or away, but also the speed it is moving. –Larger Doppler effect = greater speeds –Smaller Doppler effect = slower speeds Hubble’s law - the farther the galaxy is from us, the faster it is moving away.

The Beginning Hubble’s law points toward the universe expanding. –Book example = raisin bread dough rising Galaxies are all moving away from each other –Exception to the rule are galaxies within the same galaxy cluster.

Raisin Bread Rising

Our perspective:

Galaxies at Time 1 and Time 2

What if you lived here?

Universe is expanding:

But we are NOT the center:

See! NOT the center!

Big Bang Theory States that all matter in the universe was in one hot, super massive ball b.y.a. there was an “explosion” All the mass in the universe began expanding outward from that point. Evidence –Red shifts –Cosmic background radiation - like the “boom” of the explosion. Unlike a boom, we “hear” it from EVERY direction.

@NeilTyson

THE BIG BANG

Big Bang Movie expanding_univ.mov

The End Expand forever? –Continued cooling and expansion of all matter in the universe Or, The Big Crunch? –Gravity takes over –Expansion stops and reverses –Eventually colliding into one point Proof? –Mass points to expansion option; favored by scientists. –Dark matter could indicate crunching option

Our Neighboring Galaxies-Visible Light

Same picture: X-Ray Vision!

So What?! X-Ray info tells us how much gravity is squeezing the matter in that galaxy cluster. Gravity = mass; therefore scientists have found that there is too much gravity for the amount of mass we can find. Infer that there must be mass that is invisible. Called dark matter.

Dark matter Doesn’t give off light/energy. Believed to be 10X the amount of mass in the visible galaxy clusters Thought to make up 23% of universe. Found as “halo” around galaxy clusters.

What do we mean by dark matter (and dark energy)? Dark matter and dark energy have never been directly observed, but each has been proposed to exist because it seems the simplest way to explain a set of observed motions in the universe. Dark matter is the name given to the unseen mass whose gravity causes the observed motions of stars and gas clouds. Dark energy is the name given to whatever may be causing the expansion of the universe to accelerate.

Dark Matter

Galaxy Clusters: X-ray & data extrapolation

The Universe

How do they study it?