The Edge Of Inifinty

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The Edge Of Inifinty

• Supermassive Black Holes in the Universe
• By Fulvio Melia

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What is a Black Hole?

• An area of space-time where the gravitational
  force is so strong that not even light can escape
• Normal Black Holes 10-20 solar masses
• Supermassive gt1000 solar masses, possibly
  billions

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If Nothing Can Escape, How Can We Detect Them?

• Radiation from infalling matter
• Gravitational clues
• Ejected Plasma

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Where Are They?

• Nuclei of galaxies with a central bulge
• Astronomers believe billions of them exist in the
  universe

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How Do They Form?

• Highly Debated
• Collapse of a supernova?
• Accretion?
• Galactic Collision?
• Merging of smaller black holes?

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Is the Universe a Black Hole?

• Schwarzschild Radius scales directly with its
  total mass but for a given mass the density drops
  off inversely with the enclosed volume (radius
  cubed)
• 100kg person r 10-23cm, p 1073g/cm3
• Sun r 3km, p 1016g/cm3
• 100 million Suns r 2.4x108km p 1g/cm3
• Known Universe r 12 billion light years, p
  5x10-30g/cm3
• Density is equivalent to 6 hydrogen atoms per m3
• Of all the possible average densities that the
  universe could have had, why is it that the one
  with which it is apparently endowed is so
  strikingly close to the value needed to create an
  event horizon at the edge of what is visible?