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Announcements •Don’t forget about your project. Presentations will be next Monday May 1 at 3:20pm. A written paper is also due at the same time. Exam 4 is after the presentations •Last exam will cover from Chapter 9 Rotating Black Holes through Chapter 13. All essay exam…pick five from a list of eight to ten. Exam 4 samples have been updated to include Chapter 13 After Inflation, the strong nuclear force “freezes out” and the universe enters the Quark Epoch The universe is now a quark-gluon plasma. The quarks were created in the Unified Era and move around almost unbound during the Quark Era Gluons are the exchange particles that bind quarks together During the Quark Epoch there were three forces The strong force governs quarks and gluons, the electroweak force governs charges and leptons as well as exotic particles and gravity governs the large scale structure of the universe. The Electroweak Force won Weinberg, Salam and Glashow the Nobel Prize in Physics in 1979 James Clerk Maxwell unified the Electric force with the Magnetic force into the Electromagnetic force. Glashow, Salam and Weinberg unified the Electromagnetic force with the Weak force into the Electroweak force For a while the quarks still roamed free but that eventually changed Quark-Gluon Plasma Quarks confined into hadrons Finally, the temperature cools to 1015 degrees and the Weak force “freezes out” At this point, the universe enters the Lepton Epoch As the temperature decreased only electrons were left The heavier muon and tau particles stopped being created because there wasn’t enough energy density to produce them Once the temperature fell to 1010 degrees certain reactions resulted in more protons than neutrons p e n ne p Because the neutron is more massive, the reaction that creates it is less likely than the one that creates a proton When the temperature falls to a billion Kelvin nucleosynthesis begins n p d The first step forms deuterium, a heavy isotope of hydrogen. At first the deuterons are broken up by the high energy gamma rays. Once the temperature cools enough they can survive long enough for the next step. H-H and D-H fusion starts to produce 4He Once 4He is made other fusions occur for a short while 4 He He Li 4 He He Be 7 Be e Li 3 7 3 7 7 Since 7Li is easily destroyed, the abundance of this isotope in the universe gives us fundamental information about this period of time The relative abundance of certain isotopes restricts the baryon matter density of the universe The best current estimates say the baryonic matter density is only 0.04 times the critical density For several hundred thousand years after the end of nucleosynthesis the universe was a plasma The plasma was denser than the surface of the sun so it was opaque to light Finally, the density of mass became equal to the density of energy Once matter became dominate the next important event was Recombination After Recombination matter started to clump together Watch Cosmic Evolution WMAP video Measuring the Universe What parameters do we measure? H0: current value of the Hubble “constant” k: curvature parameter WM: mass/energy density parameter WDM: dark matter density parameter WL: cosmological constant parameter q0: deceleration parameter Determining these parameters will determine which model best fits the universe Measuring H0 Simple enough: measure the recessional velocity and distance to a bunch of galaxies and plot the data on a Hubble plot…the slope equals H0 Measuring H is a little more complicated Shape factor and mass density affect H, especially when you get to large Z