Pentcho Valev
2017-10-21 16:48:07 UTC
In my view, the following dialog marks the beginning of a sweeping revolution in cosmology:
http://backreaction.blogspot.bg/2017/10/space-may-not-be-as-immaterial-as-we.html
Sabine Hossenfelder: "Is Space-Time Fluid? We have known at least since Einstein that space and time are inseparable, two hemispheres of the same cosmic brain, joined to a single entity: space-time. Einstein also taught us that space-time isn't flat, like paper, but bent and wiggly, like a rubber sheet. Space-time curves around mass and energy and this gives rise to the effect we call gravity. That's what Einstein said. But turns out... [...] That space itself isn't fundamental but made of other things is one way to approach the problem. Not everyone likes the idea. What irks physicists most about giving substance to space-time is that this breaks Einstein's bond between space and time which has worked dramatically well - so far. Only further experiment will reveal whether Einstein's theory holds up."
Arun: "How does a fluid analog of general relativity avoid having a preferred reference frame?"
Sabine Hossenfelder: "Arun, it doesn't. It's why I write it breaks the union between space and time." [END OF QUOTATION]
Sabine Hossenfelder is on the right track. Not exactly space but what is called vacuum is "made of other things". The "other things" slow down light - this explains the Hubble redshift (in a STATIC universe):
"...explains Liberati. "If spacetime is a kind of fluid, then we must also take into account its viscosity and other dissipative effects, which had never been considered in detail". Liberati and Maccione catalogued these effects and showed that viscosity tends to rapidly dissipate photons and other particles along their path, "And yet we can see photons travelling from astrophysical objects located millions of light years away!" he continues. "If spacetime is a fluid, then according to our calculations it must necessarily be a superfluid. This means that its viscosity value is extremely low, close to zero"." https://phys.org/news/2014-04-liquid-spacetime-slippery-superfluid.html
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." http://www.nature.com/news/superfluid-spacetime-points-to-unification-of-physics-1.15437
"Some physicists, however, suggest that there might be one other cosmic factor that could influence the speed of light: quantum vacuum fluctuation. This theory holds that so-called empty spaces in the Universe aren't actually empty - they're teeming with particles that are just constantly changing from existent to non-existent states. Quantum fluctuations, therefore, could slow down the speed of light."
https://www.sciencealert.com/how-much-do-we-really-know-about-the-speed-of-light?perpetual=yes&limitstart=1
The "preferred reference frame" does not affect the validity of the principle of relativity in its traditional usage but of course orcs will be raging for some time:
Lubos Motl: "Take Backreaction's newest blog post - something promoting the aether. She has totally ignored the LIGO+EM discovery of the golden binary. One of the things it implies is that the speed of light of all frequencies and the speed of gravitational waves are the same with a huge precision. Needless to say, it kills any kind of an aether theory much more than the data available before that. Hossenfelder just chooses the moment a few days after this huge confirmation of special relativity to promote crackpot theories involving aether and doesn't even realize the irony of it. She either doesn't have the slightest clue about the link between experiments or theory; or she just totally and arrogantly chooses to ignore these links entirely." https://motls.blogspot.bg/2017/10/27-cheers-for-shut-up-and-calculate.html
Pentcho Valev
http://backreaction.blogspot.bg/2017/10/space-may-not-be-as-immaterial-as-we.html
Sabine Hossenfelder: "Is Space-Time Fluid? We have known at least since Einstein that space and time are inseparable, two hemispheres of the same cosmic brain, joined to a single entity: space-time. Einstein also taught us that space-time isn't flat, like paper, but bent and wiggly, like a rubber sheet. Space-time curves around mass and energy and this gives rise to the effect we call gravity. That's what Einstein said. But turns out... [...] That space itself isn't fundamental but made of other things is one way to approach the problem. Not everyone likes the idea. What irks physicists most about giving substance to space-time is that this breaks Einstein's bond between space and time which has worked dramatically well - so far. Only further experiment will reveal whether Einstein's theory holds up."
Arun: "How does a fluid analog of general relativity avoid having a preferred reference frame?"
Sabine Hossenfelder: "Arun, it doesn't. It's why I write it breaks the union between space and time." [END OF QUOTATION]
Sabine Hossenfelder is on the right track. Not exactly space but what is called vacuum is "made of other things". The "other things" slow down light - this explains the Hubble redshift (in a STATIC universe):
"...explains Liberati. "If spacetime is a kind of fluid, then we must also take into account its viscosity and other dissipative effects, which had never been considered in detail". Liberati and Maccione catalogued these effects and showed that viscosity tends to rapidly dissipate photons and other particles along their path, "And yet we can see photons travelling from astrophysical objects located millions of light years away!" he continues. "If spacetime is a fluid, then according to our calculations it must necessarily be a superfluid. This means that its viscosity value is extremely low, close to zero"." https://phys.org/news/2014-04-liquid-spacetime-slippery-superfluid.html
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." http://www.nature.com/news/superfluid-spacetime-points-to-unification-of-physics-1.15437
"Some physicists, however, suggest that there might be one other cosmic factor that could influence the speed of light: quantum vacuum fluctuation. This theory holds that so-called empty spaces in the Universe aren't actually empty - they're teeming with particles that are just constantly changing from existent to non-existent states. Quantum fluctuations, therefore, could slow down the speed of light."
https://www.sciencealert.com/how-much-do-we-really-know-about-the-speed-of-light?perpetual=yes&limitstart=1
The "preferred reference frame" does not affect the validity of the principle of relativity in its traditional usage but of course orcs will be raging for some time:
Lubos Motl: "Take Backreaction's newest blog post - something promoting the aether. She has totally ignored the LIGO+EM discovery of the golden binary. One of the things it implies is that the speed of light of all frequencies and the speed of gravitational waves are the same with a huge precision. Needless to say, it kills any kind of an aether theory much more than the data available before that. Hossenfelder just chooses the moment a few days after this huge confirmation of special relativity to promote crackpot theories involving aether and doesn't even realize the irony of it. She either doesn't have the slightest clue about the link between experiments or theory; or she just totally and arrogantly chooses to ignore these links entirely." https://motls.blogspot.bg/2017/10/27-cheers-for-shut-up-and-calculate.html
Pentcho Valev