PHYS 183 Lecture Notes - Before Present

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Published on 12 Apr 2013
School
McGill University
Department
Physics
Course
PHYS 183
Professor
Lecture 34: April 12th, 2013
the final will cover everything we have done in class
it will be the same format as the midterms and same difficulty, but approximately
100 questions (3x length of midterms)
Monday and Tuesday lectures are both cancelled
we talked about on Wednesday how the fate of the universe depends on the amount
of dark matter
our universe appears to be an accelerating universe (it appears to be speeding
up/expanding faster) due to something called dark energy
dark energy is also unknown stuff, but it is something that is causing the universe to
accelerate even faster than it would be from the original explosion
evidence for the acceleration? look-back time
the type of universe we live in changes the age of the universe we live in
if the universe accelerates and expands forever it will eventually become cold and
dark as matter is separated, but who knows what other surprises are out there
why do we think that the universe is expanding at this accelerated rate? we do not
know
o dark matter gets diluted (density is going down) with expansion, but dark
energy doesn’t
o since dark matter is becoming diluted, the gravitational pull is getting
diluted as well
o but we think that dark energy doesn’t get diluted
o so as the universe gets larger, you have to create more of it
o so then dark energy starts to take over
o once the dark energy is more dominant, the acceleration “takes off”, it is a
cosmic jerk
o dark energy and dark matter are completely independent, they aren’t
related
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Document Summary

Lecture 34: april 12th, 2013 the final will cover everything we have done in class it will be the same format as the midterms and same difficulty, but approximately. Monday and tuesday lectures are both cancelled. We talked about on wednesday how the fate of the universe depends on the amount of dark matter. Our universe appears to be an accelerating universe (it appears to be speeding up/expanding faster) due to something called dark energy. Dark energy is also unknown stuff, but it is something that is causing the universe to accelerate even faster than it would be from the original explosion.

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