Interesting post from Sara Reardon in Symmetry (A joint Fermilab/SLAC publication):
In 2008, Fermilab particle astrophysicist Craig Hogan made waves with a mind-boggling proposition: The 3D universe in which we appear to live is no more than a hologram. Now he is building the most precise clock of all time to directly measure whether our reality is an illusion.
The idea that spacetime may not be entirely smooth — like a digital image that becomes increasingly pixelated as you zoom in – had been previously proposed by Stephen Hawking and others. Possible evidence for this model appeared last year in the unaccountable “noise” plaguing the GEO600 experiment in Germany, which searches for gravitational waves from black holes. To Hogan, the jitteriness suggested that the experiment had stumbled upon the lower limit of the spacetime pixels’ resolution.
Black hole physics, in which space and time become compressed, provides a basis for math showing that the third dimension may not exist at all. In this two-dimensional cartoon of a universe, what we perceive as a third dimension would actually be a projection of time intertwined with depth. If this is true, the illusion can only be maintained until equipment becomes sensitive enough to find its limits.
“You can’t perceive it because nothing ever travels faster than light,” says Hogan. “This holographic view is how the universe would look if you sat on a photon.”
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