I recently completed reading an article in Scientific American on black holes (a link to the article is below).
The authors, Theodore Jacobson and Renaud Parentani, made the argument that sound waves in fluid (under certain conditions) behave similarly to light waves in space. I was most caught by some statements towards the end of the article; in particular, two points.
The first one has to do with the frame of reference of an observer seeing the Hawking emissions from black holes. Specifically, the infinite redshift problem of Hawkings theory may be avoided if the macroscopic flow of the environment surrounding a black hole changes significantly more slowly than the changes at the molecurlary state. In fluid, the wavelength of phonons bottom out at the intermolecular distance. The frame of reference problem arises because observation of phonons in fluid have an implied frame of reference. There is no implied frame of reference in space when discussing black holes. Apparently, having an implied frame of reference might violate relativity.
This is where I have the problem. It seems that there must be a Universal Frame of Reference that must reflect a general null movement through space and time (as opposed to 0 movement through space and time -- 0 Space / 0 Time). The presence of all the objects in the universe -- all moving at different speeds and directions, all at the same time -- implies that they all share a common frame of reference. We are all here together. Yes, there are likely other frames of reference that exist, such as Near Light Speed, Light Speed and the aforementioned 0 Space / 0 Time. However, the majority of the universe must share the Universal Frame of Reference, which represents no special or extreme movement with respect to other universal bodies.
This leads to the second point, when one considers the makeup of space and time such that a frame of reference can be said to exist.
In the article, the authors refer to the possibility that continuous space and time might be abandoned in order to unify general relativity and quantum mechanics. They mention that even Einstein considered this possibility very late in his life. Einstein thought that abandoning the field concept would destroy his lifes work and all of modern physics.
Balderdash, I say.
It all depends upon your frame of reference. If one views the ocean from beyond the earths atmosphere, it is a single, blue, continuous, smooth field. If one views it from a few hundred meters above, it is still single and continuous, but no longer smooth and not necessarily blue. When one examines the water at the molecular level, one cannot even say that it is single and continuous.
I believe space operates this way as well. When considered at the Universal Frame of Reference level -- large enough to encompass galaxies, space is entirely smooth ane continuous. A single field at which level general relativity operates without paradox.
However, as one examines space in finer detail, it looses its smoothness. Like water, space is filled with eddies, streams and flows. Within those structures are molecules that are not smooth or continuous. At the sub-molecular level is the underlying structure, the quantum fields and rules that are not evident from further away.
In this way, photons which are created at the event horizon, which should start with infinite redshift in a smoothly contiguous space time field, actually are created in accordance to quantum rules and are "bottomed out" in terms of a wavelength. This way they don't have to start with an infinite wavelength at all.
Scientific American: An ECHO of Black Holes [ PHYSICS ]
Sound waves in a fluid behave uncannily like light waves in space. Black holes even have acoustic counterparts. Could spacetime literally be a kind of fluid, like the ether of pre-Einsteinian physics?