5 x 10^113 J/m^3
Hi Tom
At the space-time quantum level the energy density is the rather large figure I've written above. At the electron orbital radius it's somewhat lower, but still pretty huge... 4 x 10^14 J/m^3.
You know of the Many Worlds Interpretation - what's little appreciated is that it spawns off new 'Worlds' at an incredible rate. All that quantum space-time foam might just be those 'Worlds' pinching off from our history.
Our Hubble horizon encloses something like 1.5 x 10^55 kg, so 10^96 kg/m^3 means about 6 x 10^40 Worlds spawn off per cubic metre per second.
Owww... my head hurts.
Adam
