NSCI 110_Unit 4_From Dust to Dust.pdf - The Big Bang Regent University Up Unto This Point The universe is very large Parallax Cepheid variable stars

NSCI 110_Unit 4_From Dust to Dust.pdf - The Big Bang Regent...

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The Big Bang Regent University
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Up Unto This Point The universe is very large Parallax, Cepheid variable stars, Hubble’s Law General Relativity includes the most accurate set of equations ever written Began with several immediate tests: precession of Mercury’s perihelion, 1919 eclipse, redshift of space The universe is expanding—it was once together What do we expect to see if it was once together? It was once in thermal equilibrium—at some point it cooled enough so atoms would no longer be ionized (Cosmic Microwave Background) An astrophysics group was building a machine to measure it and got scooped!
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Where do We Go From Here? Before the Cosmic Microwave Background The first 20 minutes of our universe Observations of the first 20 minutes Stealing God’s Glory?
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Before the CMB The CMB: an era when the universe cooled so atoms could form What’s smaller than an atom?
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Before the CMB The CMB: an era when the universe cooled so atoms could form What’s smaller than an atom? Was the universe ever so hot that nuclei could not even form? You can predict the temperature of the universe from the Friedman Equations You find that 380,000 years before the CMB the temperature was hot enough to break apart even nuclei At this moment (~1 second after the universe ‘began’) The temperature is so hot that no nuclei can even form The temperature is also hot enough to convert protons to neutrons
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The Delicate Dance The universe cools and no new neutrons can form—how many neutrons and protons exist at this time? Can estimate this assuming a Maxwell-Boltzmann Distribution 𝑁𝑁 𝑛𝑛 𝑁𝑁 𝑝𝑝 = 𝑚𝑚 𝑛𝑛 𝑚𝑚 𝑝𝑝 3 / 2 𝑒𝑒 𝑚𝑚 𝑛𝑛 −𝑚𝑚 𝑝𝑝 𝑐𝑐 2 𝑘𝑘 𝑏𝑏 𝑇𝑇 When the universe cools enough for nuclei to form, there is 1 neutron for every 5 protons Maxwell quote: The only desire which I can have is like David to serve my own generation by the will of God, and then fall asleep. At this temperature, all the neutrons start to decay unless they get married with a proton forming a nuclei (they only have 15 minutes to pair up before half of them are gone!)
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The Clock is Ticking Half of the neutrons will be gone in just 610 seconds All of the neutrons would be gone in a single day Where can they go? 𝑝𝑝 + 𝑛𝑛 → 𝐷𝐷 𝐷𝐷 + 𝑝𝑝 → 3 𝐻𝐻𝑒𝑒 𝐷𝐷 + 𝐷𝐷 → 4 𝐻𝐻𝑒𝑒 This epoch is radiation dominated (one billion photons for every proton or neutron), and it would be extremely rare for 3 baryons to collide at once so this process can only occur in one proton/neutron steps
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The End of BBN (Big Bang Nucleosynthesis) After 20 minutes the whole process is done The temperatures are too low to form any nuclei The p/n ratio will keep increasing and all unbound n will decay into protons What remains at this time
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  • Summer '18
  • Dr. Marshall Bowles
  • Big Bang, Redshift, Physical cosmology, Cosmic microwave background radiation

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