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IAS IAS April 9, 2008April 9, 2008
Lawrence Rudnick, University of Minnesota Lawrence Rudnick, University of Minnesota in collaboration with Shea Brown & Liliya Williamsin collaboration with Shea Brown & Liliya Williams
A UniverseA UniverseFull ofFull of
NOTHINGNOTHING
EVERYWHERE, EMPTINESS air, atoms, stars, universe
WHAT WE DON’T SEE
THE CURIOUS VACUUM
FINDING the BIGGEST NOTHING
EVERYWHERE EMPTINESS
AIR
INTO THE ATOM
Lord Ernest Rutherford1911 Gold Foil Experiment
PLANETS & STARS PLANETS & STARS
The 3-D Universe: TIME & SPACE
0.0001 sec
100’s years
5 min
1000’s years
Looking back – time and space
Structures in the Universe
Words Words of of
WisdoWisdommThe Universe is almost empty,
from sub-atomic to cosmic scales
WHAT WE DON’T SEE
“DARK” Matter
Behind the scenes…
“DARK” Energy
Behind the scenes…
Behind the scenes...
Words Words of of
WisdoWisdomm
The Universe is almost empty, from sub-atomic to cosmic scales
The most important stuff is what we DON’T see (dark matter & energy)
THE CURIOUS THE CURIOUS VACUUMVACUUM
“That gravity should be innate, inherent and essential to matter, so that one body may act upon another at a distance through a vacuum, without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity, that I believe no competent faculty of thinking, can ever fall into it. Gravity must be caused by an agent acting constantly according to certain laws; but whether this agent be material or immaterial, I have left to the consideration of my readers.” I. Newton, 25 Feb, 1693
• Making a vacuum
• The luminiferous aetherwhat medium carries light?
• What’s left in the vacuum?
THE CURIOUS THE CURIOUS VACUUMVACUUM
Evangelista Torricelli 1640s
Von Guericke – the Magdeburg spheres (1654)
WHAT CARRIED THE LIGHT?
Michelson-Morley 1881, 7
Is the vacuum empty?
The vacuum is that which is left in a vessel after we have removed everything from it that we can remove from it. James Clerk Maxwell 1892
Vacuum Waves
• Casimir effect: 1948
Vacuum Waves
• Casimir effect
Radioactive Decay
210Po 206Pb + 4He
E*t > h/2
Radioactive Decay
energy from the vacuum
Have we reached the ultimate vacuum?
Words Words of of
WisdoWisdomm
The Universe is almost empty, from sub-atomic to cosmic scales
The most important stuff is what we DON’T see (dark matter & energy)
Even the vacuum is teeming with forces (dark energy) that dominate the dynamics of the Universe
FINDING THE BIGGEST NOTHING
Early Universe – first look
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Ear
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rse
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2.73K
Early Universe – a fine look
WilkinsonMicrowaveAnisotropyProbe
Isolating the CMB Cold Spot
Early Universe
Hole in the NVSS
Early Universe “Local” Universe
Late Integrated Sachs-Wolfe (ISW) Effect
EnergyEnergyEnergyEnergy
• A CMB photon will change energy as it traverses a potential well
• -- if the well evolves during the transit.
f
iISW
rdrT
T),(2
Peebles & Ratra 2003
Void Statistics
• Very unlikely given the current void statistics, such large scales have not been investigated either in observations or simulations
Hoyle & Vogeley 2004
Average: δ = -0.94±0.02; R=(15.61±2.84) h-1 Mpc
I love talking about nothing. It’s the only thing I know anything about. (OW)
Olber’s paradox
“LOCAL” UNIVERSE
How Large of a Void is Needed?
• We can do an order of magnitude calculation to find the size of the void need to create the “cold spot”
• If we assume δ = -1 and z = 0.5-1.0, we calculate that a ~280 Mpc void is need.
• Void statistics done so far find that the probability of finding a 280 Mpc void is ~5x10-10
• Second order effects could change the size of the void(s) needed Inoue & Silk 2006, 2007
What we’ve learned...
• CMB has tiny fluctuations from Early Universe, (at 46 billion light years away) plus mysterious “cold spot”
• There is a “deficit” of radio galaxies in the same direction as the cold spot (6-10 billion light years away)
• If the radio galaxy deficit is due to an empty void, 1 billion light years across, it could be responsible for the WMAP cold spot.