l20 - Today Announcements: HW#8 is due 26 March at 8:00am...

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ISP209s7 Lecture 20 -1- Today • Announcements: – HW#8 is due 26 March at 8:00am – HW#9 is due 2 April at 8:00am – Voting for the Spring Break Story Contest is now open. Voting will close on 2 April. The winner will be announced on 4 April. • The Past – the Big Bang • The Present, Future, and Time • Black Holes, Wormholes and Back to the Future
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ISP209s7 Lecture 20 -2- A summary of the forces of nature Force Strength Carrier Acts on Range (m) Strong 1 Gluon, g quarks anything with charge quarks, electrons (leptons) , neutrinos anything with mass 10 -15 size of a proton Electromagnetic 1/137 photon infinite Weak 10 -6 Vector Bosons W +, W - ,Z 0 10 -18 Only 0.001 width of proton Gravity 6x10 -39 Graviton (?) infinite
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ISP209s7 Lecture 20 -3- Unification of Forces • Wind, Waves, push, pull, etc. – all due to the electric force and atoms pushing against each other • Electric and Magnetic – both due to the exchange of photons. Maxwell combined into electromagnetic. • Weak and electromagnetic fit into one theory called electroweak theory (Weinberg in the 1970s) • The strong force may be connected (unified with electroweak by a set of theories called supersymmetric theory) • Gravity does not yet fit in.(Maybe string theory)
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ISP209s7 Lecture 20 -4- At high temperature forces are “unified” • Current theory says at very high temperature we don’t see all the forces. We say they are “unified”. • Example: The Curie point of metals • At the start of the Big Bang the 4 forces were unified. • At the Universe cooled the forces became distinct – this is called spontaneous symmetry breaking
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ISP209s7 Lecture 20 -5- Big Bang Timeline (the early moments)
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ISP209s7 Lecture 20 -6- Picture of Events after the Big Bang What we see as we look away from the Earth
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ISP209s7 Lecture 20 -7- Why does time always move in one direction? • Inflation during the Big Bang resulted in a
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l20 - Today Announcements: HW#8 is due 26 March at 8:00am...

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