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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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.