A hundred years ago or more, when trance mediumship was in its heyday, many of the purported spirit communicators talked about the "ether" as a key to the nature of reality. At the time, the idea of the ether - often styled the luminiferous ether - was universally accepted by physicists and was well known to educated members of the public. The consensus was that some sort of extraordinarily subtle and uniform substance, as yet undetected, permeated the universe and served as a conducting medium for light waves, gravitational fields, etc.
In the years since, however, the ether has fallen out of fashion. Attempts to measure the ether proved fruitless. The consensus now is that the ether, at least in its original meaning, does not exist.
So what are we to make of the mediumistic communiques? How could the "spirits" get it so wrong? Were all the references to the ether merely products of the mediums' subconscious minds? If so, how much of the rest of the communications are similarly flawed?
Before we give up on the ether entirely, we might consider the possibility that the general idea was right, but the details assumed by physicists of the time were wrong. This is the tack taken by physicist Brian Whitworth in his recent paper Simulating Space and Time (PDF), which Ben recommended to me.
Whitworth earlier wrote a paper (PDF) arguing that the universe can be understood as a virtual reality simulation. In his new paper he expands on this idea by suggesting ways in which space and time could be created in a virtual world.
First, Whitworth posits the existence of a "grid," which he describes as "the processing screen that creates the pixels, where ... the directions of space reflect grid transfer connections [and] the passage of time reflects grid processing cycles."
The "pixels," in this scenario, are light ("cyclical patterns passed between processing nodes"), matter ("information pattern tangles that stay in a node"), and energy ("the amount of processing in any transfer").
The "nodes" in the grid are comparable to Internet Service Providers (ISPs) on the Web. As the universe expands, new nodes are added, meaning that the universe is "scalable" like the Internet. In each case, "new nodes that increase network load also add more processing. As network supply rises in tandem with network demand, the system can grow indefinitely. Scalability also shares control, which is why the Internet has no 'control centre'.... [S]haring control lets systems evolve better."
But what does all this have to do with our old friend, the ether? In Whitworth's view, the grid is the ether.
The idea of an ether that is physical like the objects it contains was shown false by the Michelson–Morley experiment, but the idea of a non-physical ether has never been contradicted:
"Since 1905 when Einstein first did away with the luminiferous aether, the idea that space is filled with invisible substances has waged a vigorous comeback."
The traditional argument against an ether is that a thin, transparent jelly-like substance permeating all space would give a standard frame of reference to all movement, which by Einstein doesn't exist. However a non-physical ether, such as the grid, is compatible both with quantum theory:
"The ether, the mythical substance that nineteenth-century scientists believed filled the void, is a reality, according to quantum field theory."
And with relativity:
"According to the general theory of relativity space without ether is unthinkable; for in such space there not only would be no propagation of light , but also no possibility of ... space and time..."
If the physical universe is a virtual reality, the new ether is the grid-screen that processes it.
When we view empty space we see nothing, just emptiness. This could mean nothing is there, as objective reality supposes, or that it is a processing host that perfectly transmits all light and matter, as proposed here. When one looks out a perfectly transparent window, the glass transmits the light from objects behind it. One sees the message of light the window passes, but not the glass medium that sends it. One only knows a glass window is there by its imperfections, by its frame surround, or by touching it.
Now imagine a world filled by a perfect transmitter with no imperfections so it can't be seen, that is all around so it has no boundary, and that transmits matter so it doesn't repel touch. If physics is information, then this is not impossible. If this medium filled every direction, one couldn't see around it. If it passed on all light perfectly, it would itself be unseen. And if we moved into it, it would just pass on the matter of our bodies on as it does light. Yet it could be known by logical inference, as is done here.
In the virtual reality conjecture, the grid is like a perfect diamond that completely fills the universe, continuously and flawlessly reflecting the images within it. Empty space then is quite "full", and the idea of “nothing” is just a figment of the human imagination. [pp. 239-240]
In other words (as I read it), the ether exists, but it is not a physical substance suffusing the cosmos. Rather, it is a grid of information-processing nodes - a network of information transfer and storage.
There is much more of interest in Whitworth's paper. I certainly didn't follow all the details on a first reading, and I intend to go back for a deeper look.
But in the meantime, it's tempting to speculate that maybe the "spirit communicators" of a hundred years ago weren't so far off, after all.