Black Holes

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Black Holes Relativity
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In this chapter you will discover

• Einsteins theory of general relativity
• space time are not separate
• how black holes arise
• surprisingly simple properties of black holes
• X rays jets of gas created near black holes

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Relativity

• Einsteins vision
• Theorized Time Distance cannot be measured
  absolutely
• Time Distance only have meaning when measured
  relative to something

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The Up Paradox

• We regard up as single direction above our
  head
• People in Australia do not stand upside-down
• So we revise our common sense
• up is defined relative to the center of the
  Earth

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What is Relative?

• A plane flies WEST from Nairobi to Quito at 1,000
  mi/hr.
• The Earth rotates EAST at the equator at 1,000
  mi/hr.
• What an observer sees depends on her/his position!

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What is Relative?

• A plane flies WEST from Nairobi to Quito at 1,000
  mi/hr.
• The Earth rotates EAST at the equator at 1,000
  mi/hr.
• An observer on the Earths surface?
• gt Would see the plane fly westward overhead

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What is Relative?

• A plane flies WEST from Nairobi to Quito at 1,000
  mi/hr.
• The Earth rotates EAST at the equator at 1,000
  mi/hr.
• An observer far away in space?
• gt Would see the plane not seem to move at all,
  and the Earth turn under it!

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Motion Reference

• Objects moving relative to one another are in
  different reference frames.
• Experience time measure distance mass
  differently

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Einsteins Vision

• 1905 Special Relativity
• Speed of Light c same for ALL observers
• No matter how fast they are moving!
• No matter what direction they are moving!

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Einsteins Vision

• 1915 General Relativity
• Acceleration upward gravitation
  downward
• And we cant tell the difference!!

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Einsteins Vision

• 1915 General Relativity
• Matter will bend space and time

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Time is affected by gravity
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Light is affected by gravity

• Gravity is warping of spacetime about an object
  with mass
• Even light is affected by gravity.

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Proof!

• Deflection of Starlight by the Sun
• 1919 Total Solar Eclipse
• Precession of Mercurys orbit
• Gravitational Redshift of light moving up
• Delay in signals from Spacecraft on Mars

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Gravity Bends Light!
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Gravity Bends Space!
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Gravity Bends Light!
Mars Orbiters Landers send radio signals to
Earth
Signals travel at speed of light across solar
system
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Radio Signals from Mars
Signals bent by gravitation of the Sun
Signals take longer to reach us than predicted
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Special Relativity Consequence

• Length is different for moving observers
• Stationary observers measure longer lengths
• Moving objects appear to be shorter
• Time is different for moving observers
• Stationary observers measure longer times
• Time for Moving objects appears to be less
• Energy and Mass are related (E mc2)

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A ball in moving train
Seen from INSIDE the train, the ball simply goes
UP and DOWN in a certain time tinside observer
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A ball in moving train
Seen from OUTSIDE the train, the ball goes UP and
DOWN, but ALSO sideways at the speed of the
train, say in a certain time toutside observer
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A ball in moving train
The faster the train is moving, the faster the
ball appears to be going to an outside observer
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A ball in moving train
The faster the train is moving, the faster the
ball appears to be going to an outside observer,
covering a longer distance in that same time
toutside observer
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So what??

• Replace the Ball with a Beam of Light
• And
• Suppose both inside and outside observers assume
  the speed of light is the same

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A light beam in moving train
For the observer in the train, the light moves up
and down at the speed of light, in a time
tinside observer
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A light beam in moving train
For the observer OUTSIDE the train, the light
travels farther .
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A light beam in moving train
For the observer OUTSIDE the train, the light
travels farther . but if it moves at the same
speed of light it must take longer! toutside
gt tinside
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Consequences!
Time measured by someone moving is different than
time measured by someone who isnt! toutside
observer gt tinside observer
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Consequences!
Time measured by someone moving is different than
time measured by someone who isnt! toutside
observer gt tinside observer The faster you go,
the greater the difference in your perception of
time vs. for someone not moving!
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Proof!

• Decay of Subatomic Particles (Muons) (cf.
  https//www.youtube.com/watch?vqgC-NDpt-mw)
• Actual Aircraft Travel (Hafele-Keating exp.)
  (cf. http//www.youtube.com/watch?vgdRmCqylsME)
  
• GPS satellites!
• (cf. https//www.youtube.com/watch?v30KfPtHec4s
  (cf. https//www.youtube.com/watch?vzQdIjwoi-u4
  )
• Nuclear Colliders

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Additional Consequences of Special Relativity

• Time as measured by stationary observer is longer
• Length as measured by stationary observer is
  longer
• Mass as measured by stationary observer is more
• All compared with measurements made by moving
  observers

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Additional Consequences of Special Relativity

• Time is relative! (https//www.youtube.com/watch?
  v02tchltLm3c)
• Length as measured by stationary observer is
  longer
• Mass as measured by stationary observer is more
• All compared with measurements made by moving
  observers

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Traveling to the Stars
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The Doppler Shift Explained through Relativity
Speed of light is measured to be identical but
observed frequency (wavelength) is not!
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So what happens to light near a VERY massive
object?
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Black Holes General Relativity
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Black Holes Theory!

• After massive star supernova, if core mass gt 3
  M?, gravity will be too strong for even neutron
  degeneracy to stabilize star.

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Black Holes Theory!

• The star will collapse into a singularity
• zero size
• Infinite density
• Enormous gravitational pull IF you get too close

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Black Holes - Theory

• The star becomes infinitely small.
• it creates a hole in the Universe
• Since 3 M? or more are compressed into an
  infinitely small space, the force of gravity NEAR
  to the star is HUGE!!!
• WARNING!!
• Newtons Law of Gravity is no longer valid !!

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Black Holes - Theory

• Defined by their event horizon
• Radius inside of which light cannot escape
  (Schwarzschild radius)

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Black Holes - Theory

• Defined by their rotation
• Rapidly rotating holes will affect space around
  them

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Rotating Black Holes drag space around them
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Black Holes - Theory

• Defined by their event horizon
• Radius inside of which light cannot escape
  (Schwarzschild radius)
• Defined by their rotation
• Rapidly rotating holes will affect space around
  them
• But how can they be observed??

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Black Holes affect Time in nearby space
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Black Holes affect matter in nearby space, too
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• Cygnus X-1
• A candidate for a stellar-sized black hole
• 11x more massive than Sun.
• 8000 ly away.

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Black Holes can emit jets of radiation
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Black Holes come in different sizes
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Black Holes at the Centers of Galaxies
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Black Hole at Center of Milky Way!
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Intermediate Mass Holes?
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Gamma Ray Bursters
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Gamma Ray Bursts as indicators of Black Holes
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Detecting the Gravitational Dance of Black
Holes?
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