How bizarre is our universe?

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How bizarre is our universe?

• Start with the Big Bang

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GUT Era lasts from Planck time (10-43 sec) to
end of GUT force (10-38 sec). At that point,
inflation occurs as the strong forces separates
from gravity releases energy (first kinetic,
then thermal)
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Recall that forces unify at high temperatures
Four known forces in universe Strong Force
Electromagnetism Weak Force Gravity
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Four separate forces today(t13.75 billion years
after Big Bang)

• Particle with mass? Affected by gravity.
• Particle with colour charge? Affected by
  strong force.
• Particle with flavour charge? Affected by weak
  force.
• Particle with electric charge? Affected by
  electromagnetic force.
• (The above is a simplification, but useful.)

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Three separate forcesat tlt10-30 seconds after
Big Bang

• Particle with mass? Affected by gravity.
• Particle with colour charge? Affected by
  strong force.
• Particle with flavour or electric charge?
  Affected by electroweak force.

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Two separate forcesat tlt10-38 seconds after Big
Bang

• Particle with mass? Affected by gravity.
• Particle with colour, flavour or electric charge?
  Affected by GUT force.

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Only one force (we think)at tlt10-43 seconds
after Big Bang

• Particle with mass, colour, flavour or electric
  charge? Affected by quantum gravity force.

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Future of the UniverseLet 1 millisecond
represent 1 billion years

• 1 msec runaway greenhouse effect on Earth
• 0.1 second only 1 galaxy in observable universe
• 1 second no more stars form
• 10 seconds all stars have stopped fusion
• 2 minutes all solar systems have been disrupted
• 120 days all stars have been ejected from
  galaxies
• 32,000 years all orbits decayed via gravity
  waves
• 100 trillion years protons have all decayed

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Future of the Universe

• Now let 1 second represent 100 trillion years
• 1 second protons have all decayed
• 100 trillion years stellar-mass black holes
  start evaporating
• Now let 1/100 trillionth of a second represent
  100 trillion years
• 1 second stellar-mass black holes start
  evaporating
• 100 trillion years all black holes have
  evaporated
• thats how long 10100 years is.
• Universe is cold, dark, nearly empty.

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Hawking radiation black hole evaporation

• If nothing escapes a black hole, how can it
  evaporate?
• By quantum fluctuations

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Quantum fluctuations

• On the smallest possible scales, the universe
  doesnt play by normal rules.
• Particle/antiparticle pairs can appear
  disappear, if they last for a short enough time
• electron-positron pairs can last for 10-22
  seconds
• proton-antiproton pairs have higher mass-energy
  and can last for only 10-25 seconds (at most)
• So on extremely small scales, the amount of
  energy in existence at one time in one spot
  fluctuates

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Hawking radiation black hole evaporation

• If nothing escapes a black hole, how can it
  evaporate?
• Quantum fluctuations are stronger when gravity is
  stronger, and the smallest black holes have the
  strongest gravity at their event horizons
• So what happens if a particle and antiparticle
  both appear near the event horizon of a black
  hole, but one falls in and one flies away?

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Hawking radiation black hole evaporation

• If nothing escapes a black hole, how can it
  evaporate?
• Quantum fluctuations are stronger when gravity is
  stronger, and the smallest black holes have the
  strongest gravity at their event horizons
• So what happens if a particle and antiparticle
  both appear near the event horizon of a black
  hole, but one falls in and one flies away?
• Then from our point of view, the black hole has
  emitted a particle (or antiparticle) and has lost
  mass!
• So black holes should eventually evaporate, and
  the smallest ones (e.g., from LHC) will evaporate
  first.

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Dark energy and the fate of our universe

• 100 billion years acceleration of universe
  redshifts all light from beyond the FMW beyond
  detection

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Dark energy and the fate of our universe

• 100 billion years acceleration of universe
  redshifts all light from beyond the FMW beyond
  detection
• Beyond that, we dont know enough about dark
  energy to know what it might do. Some ideas

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Dark energy and the fate of our universe

• 100 billion years acceleration of universe
  redshifts all light from beyond the FMW beyond
  detection
• Beyond that, we dont know enough about dark
  energy to know what it might do. Some ideas
• Big Rip happens if dark energy is a phantom
  energy which grows stronger with time and rips
  apart planets, molecules, nuclei, nucleons.

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Dark energy and the fate of our universe

• 100 billion years acceleration of universe
  redshifts all light from beyond the FMW beyond
  detection
• Beyond that, we dont know enough about dark
  energy to know what it might do. Some ideas
• Big Rip phantom energy grows stronger with
  time and rips apart planets, molecules, nuclei,
  nucleons.
• Standard dark energy yields accelerating
  universe but no big rip vacuum energy is
  constant with time

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Dark energy and the fate of our universe

• 100 billion years acceleration of universe
  redshifts all light from beyond the FMW beyond
  detection
• Beyond that, we dont know enough about dark
  energy to know what it might do. Some ideas
• Big Rip phantom energy grows stronger with
  time and rips apart planets, molecules, nuclei,
  nucleons.
• Standard dark energy yields accelerating
  universe but no big rip vacuum energy is
  constant with time
• Decaying dark energy acceleration stops,
  reverses?

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Dark energy and the fate of our universe

• 100 billion years acceleration of universe
  redshifts all light from beyond the FMW beyond
  detection
• Beyond that, we dont know enough about dark
  energy to know what it might do. Some ideas
• Big Rip phantom energy grows stronger with
  time and rips apart planets, molecules, nuclei,
  nucleons.
• Standard dark energy yields accelerating
  universe but no big rip vacuum energy is
  constant with time
• Decaying dark energy acceleration stops,
  reverses?
• Wont know fate of universe for sure until we
  understand dark energy. (If then!)

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So much for the end of the universethe universe
seems to go fromBig Bang to Big Whimper.But
what about the beginning?What caused the Big
Bang?
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What caused the Big Bang?

• Currently (always?), science runs out of answers
  to why? questions at this point.
• But cosmologists have lots of ideas!

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What caused the Big Bang?

• Currently (always?), science runs out of answers
  to why? questions at this point.
• But cosmologists have lots of ideas!
• Conservation of energy The universes positive
  kinetic mass-energy plus its negative potential
  energy (gravitational, electroweak, and
  strong-force) can sum to zero.

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What caused the Big Bang?

• Currently (always?), science runs out of answers
  to why? questions at this point.
• But cosmologists have lots of ideas!
• Conservation of energy The universes positive
  kinetic mass-energy plus its negative potential
  energy (gravitational, electroweak, and
  strong-force) can sum to zero.
• Superstrings the current leading contender to
  deepen our understanding of the Big Bang, etc.
• Superstring theory predicts there are 10
  dimensions, not four (1 time, 3 space, and 6 very
  tiny, rolled up space dimensions)

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A two-dimensional cylinder looks like
a1-dimensional line if the width of the cylinder
is much smaller than its length
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With 6 or 7 dimensions, you get weirder geometric
shapes, but the idea is the same
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A point in spacetime would not be t,x,y,zbut
t,x,y,z,a,b,c,d,e,f maybe g
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What caused the Big Bang?

• Superstring theory predicts there are 10
  dimensions, not four (1 time, 3 space, and 6 very
  tiny compactified space dimensions)

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What caused the Big Bang?

• Superstring theory predicts there are 10
  dimensions, not four (1 time, 3 space, and 6 very
  tiny compactified space dimensions)
• Superstring theory might unify gravity and
  quantum mechanics. In this theory, all particles
  are actually vibrating 1-dimensional strings of
  the minimum possible size the Planck length
  (10-33 cm)

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What caused the Big Bang?

• Superstring theory might unify gravity and
  quantum mechanics. In this theory, all particles
  are actually vibrating 1-dimensional strings of
  the minimum possible size the Planck length
  (10-33 cm)
• Superstring theory predicts there are 10
  dimensions, not four (1 time, 3 space, and 6 very
  tiny compactified space dimensions)
• M-theory (M for membrane, a 2-D string) predicts
  11 dimensions, with the 11th spanned only by
  gravity

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What caused the Big Bang?

• Superstring theory might unify gravity and
  quantum mechanics. In this theory, all particles
  are actually vibrating 1-dimensional strings of
  the minimum possible size the Planck length
  (10-33 cm)
• Superstring theory predicts there are 10
  dimensions, not four (1 time, 3 space, and 6 very
  tiny compactified space dimensions)
• M-theory (M for membrane, a 2-D string) predicts
  11 dimensions, with the 11th spanned only by
  gravity
• Big Bang caused by (mem)branes colliding in that
  11th dimension? Cyclic Big Bangs?

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What caused the Big Bang?

• Did the Big Bang occur as a quantum fluctuation
  in another universe?

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Quantum energy fluctuations quantum mass
fluctuations quantum spacetime fluctuations
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What caused the Big Bang?

• Did the Big Bang occur as a quantum fluctuation
  in another universe?
• or did the universe create itself? (Quantum
  fluctuations at the Planck length might be able
  to create a wormhole through which energy travels
  back in time 10-43 seconds to create the
  spacetime!)

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Wormhole in spacetime
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What caused the Big Bang?

• We dont know! (Yet)

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Just how bizarre is our universe?

• The Multiverse if our universe is finite, there
  might be other universes beyond it (separated by
  regions of eternal inflation)

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Duplicate universes?

• If our universe (or the multiverse) is infinite,
  then any part of it must eventually repeat
  itself.
• The consequences may argue against
  universe/multiverse being infinite!
• No communication between island universes,
  however.

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Just how bizarre is our universe?

• Regardless of whether our universe is finite or
  infinite, quantum mechanics might allow parallel
  universes to exist.
• Such universe might overlap with ours yet be
  impossible for us to perceive!

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Is any of this testable?
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Is any of this testable? Yes!

• (Though not all of it, and not easily)
• Analogs to Hawking radiation exist (e.g., high
  acceleration substitutes for strong gravity)
• Patterns in CMBR constrain amount of inflation,
  cyclical Big Bang theories, etc.
• Quantum gravity theory would aid in understanding
  both general relativity (wormholes) and quantum
  mechanics (parallel universes) better
• Measuring history of universes expansion will
  tell us more about dark energy (e.g., Big Rip or
  not)

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Just how bizarre is our universe?

• The Multiverse regions of eternal inflation
  separating island universes where inflation
  stopped?

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Just how bizarre is our universe?

• The Multiverse regions of eternal inflation
  separating island universes where inflation
  stopped?
• Weak Anthropic Principle why are the physical
  constants of our universe just right to allow
  stars and planets to form and thus give life a
  chance to develop?

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Just how bizarre is our universe?

• The Multiverse regions of eternal inflation
  separating island universes where inflation
  stopped?
• Weak Anthropic Principle why are the physical
  constants of our universe just right to allow
  stars and planets to form and thus give life a
  chance to develop? Because by definition, life
  will develop only in universes that allow life to
  develop (e.g., that dont have too much dark
  energy or dark matter).

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Just how bizarre is our universe?

• The Multiverse if our universe is finite, there
  might be other universes beyond it (eternal
  inflation)
• Weak Anthropic Principle why are the physical
  constants of our universe just right to allow
  stars and planets to form and thus give life a
  chance to develop? Because by definition, life
  will develop only in universes that allow life to
  develop (e.g., that dont have too much dark
  energy or dark matter).
• Only universes that can support life will have
  life in them wondering why the universe supports
  life!

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What have we learned?

• What aspects of the universe were originally
  unexplained by the Big Bang model?
• (1)     The origin of the density enhancements
  that turned into galaxies and larger structures.
• (2)     The overall smoothness of the universe on
  large scales.
• (3) The fact that the actual density of
  matter is close to the critical density.

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What have we learned?

• How does inflation explain these features of the
  universe?
• (1)     The episode of inflation stretched tiny,
  random quantum fluctuations to sizes large enough
  for them to become the density enhancements
  around which structure later formed.
• (2)     The universe is smooth on large scales
  because, prior to inflation, everything we can
  observe today was close enough together for
  temperatures and densities to equalize.
• (3) Inflation caused the universe to expand
  so much that the observable universe appears
  geometrically flat, implying that its overall
  density of mass plus energy equals the critical
  density.

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What have we learned?

• How can we test the idea of inflation?
• Models of inflation make specific predictions
  about the temperature patterns we should observe
  in the cosmic microwave background. The observed
  patterns seen in recent observations by microwave
  telescopes match those predicted by inflation.

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What have we learned?
Why is the darkness of the night sky evidence
for the Big Bang? Olbers paradox tells us that
if the universe were infinite, unchanging, and
filled with stars, the sky would be everywhere as
bright as the surface of the Sun, and it would
not be dark at night. The Big Bang theory solves
this paradox by telling us that the night sky is
dark because the universe has a finite age, which
means we can see only a finite number of stars in
the sky.