The creation of matter and energy.

Transcription

1 THE FIRST MILLION YEARS The creation of matter and energy. Recap: the Big Bang Theory 1. The Universe had a beginning. 2. The Universe is expanding. 3. The Universe is changing. 4. When the Universe was younger, it was hotter and denser. Eras of the Big Bang (photon) (proton) Dark energy dominated 3000 years 5 billion yrs 1

2 The Planck Time Time = sec Space and Time appear. Gravity begins. The Four Forces!Gravity "Holds the Solar System together.!electromagnetic force "Holds the atom together.!strong force "Holds the nucleus together.!weak force "Converts one particle into another. 4 Forces: Gravity!A long-range force!works on all matter!always attractive!exceedingly weak!dominates in stars and galaxies!carried by the graviton 2

3 4 Forces: Electromagnetism!A long-range force!works on particles with electric charge # Like charges repel # Opposite charges attract!causes light!carried by the photon 4 Forces: the Strong Force!A short-range force (size of nucleus)!holds together protons & neutrons!always attractive!works on hadrons (like the proton), not leptons (like the electron)!carried by the gluon 4 Forces: the Weak Force!A short-range force!doesn't hold anything together!works on all particles # Both hadrons & leptons!can turn one particle into another # Example: proton into neutron!carried by W +, W -, Z particles 3

4 Q. The Earth is held together by the force A. Gravity B. Electromagnetic C. Strong D. weak Q. Your body is held together by the force A. Gravity B. Electromagnetic C. Strong D. weak Force Particles: Bosons Gravity Graviton Electromagnetism Strong force Weak force Photon Gluons W +, W -, Z 4

5 Principle of Asymptotic Freedom!At high temperatures, all the forces are equal and symmetrical.!at low temperatures, the symmetry is broken. Separation of the 4 Forces TOE (Theory of Everything) GUT (Grand Unified Theory) Gravity Strong Electroweak Weak Electromagnetic Q. When radioactive Carbon-14 decays, a neutron turns into a proton. This process is caused by the force. A. Gravity B. Electro-magnetic C. Strong D. weak 5

6 The 4 Fundamental Particles u up quark e - electron down quark d! neutrino Antimatter!every particle has an antiparticle!the antiparticle has opposite electric charge!when particle meets antiparticle, they annihilate each other electron: -1 anti-electron (positron): +1 e - e + Q. A proton and an antiproton 1. attract each other 2. repel each other 6

7 2 Kinds of Matter Particles Hadrons Feel the strong force. Made of quarks. Example: the proton p + Leptons Don't feel the strong force. Fundamental particles. Example: the electron e - Leptons electron Charge -1 positron charge +1 e - e +! "! neutrino antineutrino both chargeless (neutral) Q. Which two forces does the neutrino feel? 1. Strong force & weak force 2. Electromagnetism & gravity 3. Weak force & gravity 7

8 The Quarks u Up quark: charge +2/3 Down quark: charge -1/3 d _ u Anti-Up quark: charge -2/3 Anti-Down quark: charge +1/3 _ d Note: isolated quarks are never seen. Pair Production (a) (pair production) 2 photons > electron + positron (b) (annihilation) electron + positron > 2 photons Law of Conservation of Charge The net charge is unchanged in any particle reaction. Net charge = positive charges negative charges e - # e + # Charge: = 0 Charge: = 0 8

9 Law of Conservation of Charge n p + e -? What is the charge of the mystery particle? 1. positive (+) 2. negative (-) 3. neutral The Hadrons Baryons 3 quarks Mesons 2 quarks Proton: uud Neutron: udd _ antiproton: uud antineutron: udd +Pion: ud _ -Pion: ud...and many others Note: only the proton is stable. At about 1ns, the four forces had completed separating. There followed 1 ns 1 ms 1 min - The Quark Epoch - The Lepton Epoch - The Nuclear Epoch 9

10 The Quark Epoch Age: 1 ns!all particles continually being created & destroyed: # Baryons & antibaryons leptons & antileptons!baryons, leptons and photons exist in equal numbers!end at 100 µs: Annihilation of baryons: protons! antiprotons, neutrons! anti-neutrons!1 proton & 1 neutron in a billion survived somehow. The Lepton Epoch Age: 100 µs! All leptons continually being created & destroyed: # electrons & positrons neutrinos & antineutrinos! leptons and photons exist in equal numbers (equilibrium) # 1 billion leptons and photons for each baryon.! At 2 s: Universe becomes transparent to neutrinos.! End at 1 minute: Annihilation of electrons and positrons: neutrinos & antineutrinos don t annihilate! They re still here!! 1 electron in a billion survived somehow. Q. When electrons and positrons annihilated, they created 1. protons and antiprotons 2. neutrinos and antineutrinos 3. more electrons and positrons 4. photons 10

11 The Nuclear Epoch Age: 1 minute! Formation of nuclei (He 4 mainly)! After 15 minutes, fusion ceases. # Neutrons decay into protons.! Universe is made mostly of photons and neutrinos. # 1 billion photons & neutrinos for every solitary proton. 10 protons for every He 4 nucleus + dark matter particles! Not much happens for 500,000 years. # The whole Universe is like one star. Q. During the Nuclear Era, A. There are more protons than electrons B. There are more electrons than protons C. There are equal numbers of protons and electrons The Matter Era For half a million years, the Universe is made of photons, neutrinos, protons, He 4 nuclei, and electrons 400,000 yr 200,000,000 yr!formation of atoms ("recombination")!formation of stars & galaxies 11

12 Recombination!Formation of hydrogen & helium atoms!age = 400,000 years!universe becomes transparent!photons no longer interact with matter. "Seeds" of Galaxies Slight unevenness in inflation > cool spots > clumps > galaxies Cosmic Ripples Fluctuations in the 3 K background 12

13 The Dark Ages Awaiting the birth of the first star 13