2017-02-08 20:12:29 UTC
"Indeed, Wilczek began his lecture by speaking of the profound analogy between materials and vacuum. What our naked senses perceive as empty space turns out to be a riotous environment of virtual particles fluorescing and dying away on extremely small scales of space and time, as well as fog-like fields and condensates, which permeate all space and dictate the properties of elementary particles. To give an analogy for this perplexing new picture of reality, Wilczek asks us to imagine intelligent fish in a world surrounded by water. Such creatures would perceive the water surrounding them as their version of empty space or a vacuum. "The big idea I want to convey is simply this: We're like those fish," he said. What our senses perceive as empty space is better understood as a substance, a material."
Paul Davies: "This leads to the prediction of vacuum friction: The quantum vacuum can act in a manner reminiscent of a viscous fluid."
New Scientist: "Vacuum has friction after all."
The Hubble redshift is due to the property of vacuum to slow down light - an effect analogous to slowing down moving objects by friction. The idea that vacuum constituents can slow down light is largely discussed, but only in a quantum gravity context:
Sabine Hossenfelder: "It's an old story: Quantum fluctuations of space-time might change the travel-time of light. Light of higher frequencies would be a little faster than that of lower frequencies. Or slower, depending on the sign of an unknown constant. Either way, the spectral colors of light would run apart, or 'disperse' as they say if they don't want you to understand what they say. Such quantum gravitational effects are miniscule, but added up over long distances they can become observable. Gamma ray bursts are therefore ideal to search for evidence of such an energy-dependent speed of light."
It is time to start discussing the parallel idea: that slowing down light by vacuum constituents produces the Hubble redshift (in a STATIC universe):
Nature: "As waves travel through a medium, they lose energy over time. This dampening effect would also happen to photons traveling through spacetime, the researchers found."
For not so distant stars the slowing down of light is expressed as Hubble redshift but beyond a certain distance the star light does not reach us at all (Olbers' paradox).