17th September 2014: The Smoking Gun

This is the notes I took from the TED Talk I found on a discovery earlier this year…

The Smoking Gun: Observations of the BICEP2

  • Quantum fluctuations in the shape of space-time
  • Stretched by inflation to a fraction of the size of the observable universe
  • First detection of effects involving quantum gravity
  • Take a bell and hit it with a hammer – it will ring and vibrate for quite a while then fade
  • The universe was extremely dense
  • The bell is space-time and the hammer is quantum mechanics
  • Found evidence of the ringing – what is called gravitational waves
  • Waves have long since faded – totally invisible
  • But when the universe was creating the afterglow, gravitational waves put twists in the light we see
  • Spent 3 years looking for the faint twists (BICEP2 in South Pole)
  • These twists are the signal of the ringing
  • Isn’t conclusive evidence for inflation
  • Afterglow that we see is CMB
  • BB took place 798 +/- 0.037 billion years ago
  • CMB emitted later but before that, everything was both glowing and opaque – light being absorbed as quickly as its being emitted
  • When the universe cooled down, it became transparent
  • Light emitted from then was not absorbed and has been floating round the universe ever since (CMB)
  • CMB is the fossil for light
  • Smoking gun for the idea of cosmic radiation – rapid expansion terminated in the BB
  • Inflation solved a load of problems but also erased evidence of the inflationary epoch with the exception of primordial gravitational waves which if produced with significant strength would cause twists in CMB which is what BICEP2 observed
  • IF THEY HOLD UP, they appear to directly confirm inflation
  • Below – visual representation of gravitational waves

gravitational waves

  • The idea of the multiverse being like lots and lots of bubbles
  • Given everything we know about inflation and the way it fits into the physics of quantum mechanics and gravity, the BICEP2 results make this picture very natural
  • B-mode polarisation
    • Light from the CMB is partially polarised
    • Electric field lines of incoming radiation are generally going in one direction
    • Either E-mode or B-mode
    • E-mode goes in a line away from the source whereas B-mode bends around the source
    • Observation of B-mode signal is a direct link to inflation
  • Inflation as a beginning for the universe?
    • The explosive expansion of space during inflation would have created ripples in the fabric of space. As explained below, these gravity waves should have left a signature in the polarization of the last-scattered photons (CMB).
    • Explains why the universe is flat
    • If we could detect deviations in flatness in the observable universe, it would disprove inflation but this evidence for inflation explains the flatness of the universe

To aid my understanding of this discovery I referenced the following…

http://www.physicsforums.com/showthread.php?t=431264

http://cosmology.berkeley.edu/~yuki/CMBpol/CMBpol.htm

http://profmattstrassler.com/2014/03/18/if-its-holds-up-what-might-bicep2s-discovery-mean/

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