PowerPoint Presentation Chapter 22 Opener Neutron Stars and Black Holes: Strange States of Matter

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Chapter 22--Second Half Blackholes
Black Holes Einsteins Theories of
Relativity Special Relativity Space Travel Near
Black Holes
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What is Gravity?
Newtonian Picture
Einstein's Picture
Isaac Newton (1642-1726)
the gravitational field.
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Foundations of General relativity Principle of
Equivalence It is impossible to tell, from within
a closed system, whether one is in a
gravitational field, or accelerating
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General Relativity and Gravity

• In Einsteins General Theory of Relativity,
  gravity arises from the curvature of spacetime
  continuum.
• The curvature of the spacetime continuum is
  produced by the presence of mass.
• Massive object distorts spacetime continuum more.
• Spacetime Continuum
• We are used to thinking that we have three
  physical dimensions (space), and one time
  dimension. Space and time are separate.

Spacetime is stretched near objects with large
mass, like our Earth.
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The general theory of relativity

• Published by Einstein in 1915, this is a theory
  of gravity
• A massive object causes space to curve and time
  to slow down
• These effects manifest themselves as a
  gravitational force
• These distortions of space and time are most
  noticeable in the vicinity of large masses or
  compact objects

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Orbits of Planets
Verification of General Relativity
43 arcsec/100years
The extra amount of precession of planet
Mercurys orbit is explained by GTR.
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Verification of General Relativity
Einstein 1918 - should see shift of 1.75 arc
sec. 1919 Solar Eclipse Within 20 of
Prediction! Modern Test - Radio Waves Within 1
of Prediction!
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Harvard 1959 Atomic clock in basement -
slower! Einstein 2.46x10-15 Observed
2.50x10-15
fast
slow
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• If a stellar corpse has a mass greater than about
  2 to 3 M?, gravitational compression will
  overwhelm any and all forms of internal pressure
• The stellar corpse will collapse to such a high
  density that its escape speed exceeds the speed
  of light

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Black Hole
Rs radius of event horizon is the size of
black hole. Depends upon mass and the speed of
light.
2GM
Rs
The size of a black hole!
c2
1. Photon Sphere 1.5Rs distance where light can
go into circular orbit! 2. Event Horizon
Rs distance where escape speed equals speed of
light! 3. Singularity Mathematical point at
center we dont know what it is, but it is where
the point of the funnel comes to a head if it
does?
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2
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Black Holes

• Light emitted close to the critical surface is
  severely red-shifted (the frequency is lower) and
  at the critical surface, the redshift is
  infinite. Inside the critical surface, spacetime
  is so warped that objects cannot move outward at
  all, not even light.
• Events inside the critical surface can never
  affect the region outside the critical surface,
  since no information about them can escape
  gravity.
• We call this surface the event horizon because
  it shields the outside completely from any events
  on the inside.

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Black Hole Singularity

• Singularity central point containing all of
  the mass. Known laws of physics break down.

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Tidal Forces Near a Black Hole
Matter encountering a black hole will experience
enormous tidal forces that will both heat it
enough to radiate, and tear it apart
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Gravitational Red Shift Light emitted from
compact object( strong gravity) is red shifted
The photon is giving up energy as it escapes
from the pull of the gravitational field Time
Dilation Clocks in stronger gravity fields
appear to slow down to an external observer.
Time Slows
time slowed
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Blackhole Evaporation
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The center of the Blackhole

• Could a black hole somehow be connected to
  another part of spacetime, or even some other
  universe?
• General relativity predicts that such
  connections, called wormholes, might exist for
  black holes

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Travel through a black hole and wormhole to Vega!
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Gravitational Radiation
LISA A space-based gravity wave observatory
Laser Interferometric Gravitational Observatory
(LIGO)
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