Words of Wisdom The Universe is almost empty, from sub-atomic to cosmic scales The most important stuff is what we DONT see (dark matter & energy)
THE CURIOUS VACUUM 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 aether what medium carries light? Whats left in the vacuum? THE CURIOUS VACUUM
Words of Wisdom The Universe is almost empty, from sub-atomic to cosmic scales The most important stuff is what we DONT see (dark matter & energy) Even the vacuum is teeming with forces (dark energy) that dominate the dynamics of the Universe
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
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 weve 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.