Lecture 2: General Relativity Gravity and Space Ripples

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Lecture 2 General RelativityGravity and Space
Ripples

• How is the gravitational force transmitted?
• Are black holes and worm holes real ?
• How did the universe begin and how will it end?
• Intro to basic cosmology some new insights.

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General Relativity PrimerPrice To avoid
tensor calculus would be to avoid a meaningful
expression of the ideas of GRT. To include the
mathematics, unfortunately, engenders a great
danger, that of the mathematical trees obscuring
the physical forest.

• This field equation states how the geometry of
  space is determined by the distribution of matter
  in it.
• If anyone wants to discuss geodesics or
  Christoffel symbols see me at the break !

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Space is bent by the presence of
matter/energyG Picture taken lecture notes by
Greene (NOVA site)Picture taken from The
universe in a nutshell by Hawking.
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Gravity is a very weak force on a small scale
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Principle of Equivalence

• Gravitational pull acceleration in vacuum
• Thats why space stations spin to provide
  artificial gravity.

Gravity waves and LIGO will be discussed in
lecture 9.
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Black holes are predicted by GR

• I would not recommend using a black hole for
  time/space travel. You are likely to be torn
  apart by tidal gravitational forces. The gravity
  at your feet would be much greater than at your
  head.
• Picture on left from http//www.pbs.org/nova/elega
  nt
• Picture on right by J. Bergerson. Sky Telescope
  Magazine and
• http//antwrp.gsfc.nasa.gov/apod/ap971107.html
• http//heararc.gsfc.nasa.gov/docs/blackhole.html
• http//hubblesite.org

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Wormholes might be out there and they might be
used as time machines. It is a sure thing you
could go in and come out at the same moment. Im
not sure whether you could go back in time? Going
forward in time is relatively easy and is a
consequence of SR and near light speed travel.
(Quantum wormholes are more likely).
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How did the universe begin?

• With a
• BANG

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Standard theory says that the universe started
from a tiny speck or quantum fluctuation in the
vacuum.

• String theory (or rather M-theory) suggests that
  our universe might be trapped on a 3 D brane and
  our universe may have begun from a cosmic
  collision of 3-branes.

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Cyclic model of 3-brane collisionsDiscover
magazine
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The cycle in close upDiscover magazine
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The inflationary periodSee Scientific American
next slide
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These 2 recent magazines might be of interest.
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For those of you who want to learn some of the
mathematical beauty of GR, you need to read these
books papers

• P.A.M. Dirac General theory of relativity
• R.H. Price General relativity primer AJP
  vol.50, (4) p300 (1982).
• H.C.Ohanian What is the principle of
  equivalence? AJP 45 (10) p903 (1977)
• K.S. Thorne et al. Black holes the membrane
  paradigm see also AJP 56, p395 (1988).

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Some simple books are shown here
non-mathematical.
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THE END

• 10 min break the NOVA program
• Next exciting lecture Feb 9th
• The Standard Model