Dark Matter & Dark Energy 19th March 2014

What the Universe is Made Of Neutrino = subatomic particle, emitted in nuclear reactions or when very high energy photons hit an atom. 21% = Dark Matter 74% = Dark Energy

What is Dark Matter? We can only account for about 5% of the mass of the universe with stuff we can specifically identify. Based on Newtons Theory of Gravity, we can approximate how much matter should be.

What do we think Dark Matter Exists? Rotational Curves and Individual Galaxies Galaxy orbits in clusters Gravitational lensing Looking at cosmic collisions of 2 galaxy clusters, splitting normal matter and dark matter apart.

How can we be sure that we have the right theory of gravity? We arent sure, but general relativity works so well that it takes strong evidence to adopt something else. Modified Newtonian Dynamics (MOND)

THEORY FOR DARK MATTER: MACHOS Massive Compact Halo ObjectsCandidates: White Dwarfs Brown Dwarfs

PRO We can test it.CON We have tested it, and we cant add up enough white/brown dwarfs to be enough.

THEORY FOR DARK MATTER: NeutrinosAdding up all the neutrinos to fill in the rotation curves. PRO: If Dark matter was created of these hot, fast moving particles. CON: They move too fast. The structure we see today is too clumpy, doesnt go together with predictions.

THEORY FOR DARK MATTER: Weakly Interaction Massive Particles (WIMP)

THEORY FOR DARK MATTER: String Theory Quantized Gravity LeaksPRO: Tidy. Mathematically sound.CONS: Cant be tested.

Dark Matter Recap: Massive Neutrons Matter too clumpt Supermassive Black holes Would have more signature in lensing MACHOS Microlensing experiements detect some but not enough Would requirem ore heavy elements that we can account for Monday Bullet cluster appears to rule out Parallel Not currently testable. Maybe new particle ace. Will help. WIMPS best so far.