Lol...ouch!
Look I hate to be a wet blanket here - Paul Eno seems like a very nice guy with lots of interesting stories, but this whole "multiverse" thing has gotten way out of control. So I feel compelled to set some things straight.
All of this kind of speculation arises from Hugh Everett's "many worlds interpretation," which is probably the worst of many awful consequences spawned by the Copenhagen interpretation, which in turn appears to be the worst of all the possible interpretations of quantum theory - and where all this talk of wavefunction collapse and such stems from. Let's start by being explicit about the many worlds interpretation.
According to Everett's model, for every probabilistic event that happens anywhere in the universe - all possible outcomes actually happen. To do that, an entirely distinct and separate universe must exist for every possible outcome - and there's generally an infinity of possible outcomes for every probability function (though some of them are simple binary probabilities, like up-or-down spin). So, for example, if an atom can emit a photon in any random direction governed by a probability function, then an infinite number of distinct universes exist; one for each possible outcome. And we are only aware of whatever universe is defined by one outcome of that probabilistic event. In this model there is no "wavefunction collapse," a feature of the Copenhagen interpretation which is a different interpretation of quantum mechanics that shares a common philosophical feature with the many worlds interpretation - namely, that the mathematics of quantum theory supersedes the reality it describes. In other words, the mathematics in both theories is elevated to the status of ontological preeminence, instead of a mere description of the reality it models: the wavefunction is taken to be an objective reality, instead of a mere mathematical tool to predict outcomes. Everett took this misguided notion to its logical extreme to assert that all possible outcomes represented by some outlandishly complex and indeterminable universal wavefunction, are physically real, resulting in a mind-boggling spectrum of distinct and non-interacting universes for every possible outcome of every quantum interaction no matter how small.
That's insane. According to this model, the action of the uncertainty principle at work in every mote of dust requires infinities upon infinities of complete universes (each of which appears to be more or less infinite in size). Everett's idea is like the mathematical inversion of Occam's razor - I can't even imagine a more complete rejection of that guiding scientific principle, and I doubt that anyone else could either. He's basically saying that the emission of a single photon is sufficient cause to produce an infinity of complete new universes. This is an excellent example of the kinds of philosophical nightmares that result when mathematicians take the reigns away from physicists. We'll get back to this in a minute.
For the sake of argument, let's go along with Everett's insane idea for a moment, to discuss the physical meaning of this model. The observer exists within each one of the infinities of universes that coexist at every moment, and more infinities of ourselves are required at every moment of time as the universe constantly evolves along all of the possible trajectories for every possible particle everywhere. There's no going back, or "jumping" from one universe to the other. Why? Because the conservation of energy still applies to all of those universes. If you could "jump" between universes, then all of the mass-energy of your body would instantly disappear from one universe and appear in another universe. That's contrary to the laws of physics - and not just laws, but all of the experimental evidence that we've ever collected which supports that law.
At particle accelerators all over the world, we're constantly testing the conservation of energy under all kinds of conditions, usually very extreme conditions, and we've never detected the disappearance of a single photon or particle. If we had, it would be HUGE news, because countless theorists advocating exotic physical theories involving higher dimensions, microscopic black holes and worm holes, branes, etc, would claim this discovery as evidence for their validity. So far: donuts.
And if we presume that for some unknown mystical reason, physical beings can do something that subatomic particles can't do (let's ignore the logical paradox of that statement), and one could somehow "step" into a different universe, then the vacuum left in the surrounding atmosphere where the body had been would suddenly collapse into the void left behind, initiating a powerful thunderclap that would be heard for miles. So somebody, somewhere, would have heard such a thing.
There's a dark joke in the physics community about the only definitive test of the many worlds interpretation. It goes like this: since there's always a non-zero probability of every outcome permitted by physical law, the many worlds interpretation states that if you put a gun to your head and pull the trigger, there's a universe where the gun jams, or the round in the chamber fails to go off, or some other event intervenes, and you go on your merry way in that universe. If the many worlds interpretation is correct, it's impossible to experience your own suicide. To date, no one has accepted the challenge to test the many worlds interpretation and lived to tell the tale.
Let's get back to the theoretical underpinnings of all this. The entire basis for the many worlds interpretation and the Copenhagen interpretation appears to be little more than one big historical tragedy of scientific reasoning stemming from a simple and troubling little experiment: the good old double-slit experiment. Physicists were bewildered and disturbed by the simple and confusing fact that when you shoot single photons or electrons at a wall with two parallel slits, with a detection screen behind it, the distribution pattern on the screen is an interference pattern, rather than a pair of impact sites behind each slot, which one would expect from a classical particle, like bullets fired from a gun. And this confusion yielded everything from the idea of "wave-particle duality" to the notion of "wavefunction collapse" to Hugh Everett's insane idea about infinities of infinite universes - one for every possible outcome of every probabilistic event to ever occur.
And our most brilliant physicists remained utterly perplexed by the double-slit experiment for decades, so they went along with all of this. Richard Feynman even said, regarding the double-slit experiment:
"In this chapter we shall tackle immediately the basic element of the mysterious behavior in its most strange form. We choose to examine a phenomenon which is impossible,
absolutely impossible, to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only mystery. We cannot make the mystery go away by 'explaining' how it works. We will just tell you how it works. In telling you how it works we will have told you about the basic peculiarities of all quantum mechanics."
The Feynman Lectures on Physics Vol. III Ch. 1: Quantum Behavior
Well, it turns out that they were all wrong. In 2005, a French physicist named Yves Couder performed a nifty little experiment that reproduces the results of the double-slit experiment using a purely classical system. He simply poured some oil onto a vibrating plate, and dropped some oil droplets onto it so that they bounced along the surface, making little waves with each bounce. And when they passed through a double-slit toward a detection screen, they reproduced the interference pattern of the double-slit experiment that had baffled physicists for nearly a century. The field of pilot-wave hydrodynamics was born:
It’s almost impossible to overstate the significance of this experiment on our understanding of quantum physics. We now have a completely classical explanation for quantum behavior, which restores determinism to quantum theory, refutes the Copenhagen interpretation, dashes the notion of “wavefunction collapse” (which was an ugly and insoluble conundrum to begin with), and provides a clear and sensible path forward to re-writing everything we thought we knew about quantum physics. It also spells the end for Everett’s “many worlds interpretation,” thankfully. Additionally, a new technique called "weak measurement" has provided compelling support for the pilot-wave theory. If some clever physicist had thought up Yves Couder's experiment 70-80 years ago, the history of quantum theory would almost certainly have taken an entirely different, classically deterministic direction.
In fact the biggest problem now is that the physics establishment is so deeply invested in decades of work in the wrong direction, that they’re loathe to go back and start over from scratch. All of the equations still work the same way, and yield flawless results. But our interpretation of all those equations will have to be chucked out entirely, and replaced with brand new explanations. A god-awful amount of work has to be done to restore common sense and classical understanding to our theory of the microcosm. Fortunately, huge strides have already been made: the de Broglie-Bohm pilot-wave theory has been around for decades, but most physicists ignored it because the Copenhagen interpretation was far more fashionable (and honestly I think that most quantum physicists have enjoyed the public perception of their work as some kind of exotic witchcraft that defied human reasoning – they’ll have to hand in their magic wands and cool pointy hats).
And similarly, an alternative model for quantum vacuum fluctuations has recently made huge strides, and its first major successful prediction, and now appears to be poised to overthrow the interpretation of the quantum field based on the Heisenberg uncertainty principle. It’s called stochastic electrodynamics, and it postulates that the field of “virtual particles” proposed by quantum theory is actually a field of real particles. And with only a handful of maverick physicists working on it, they’ve already managed to accurately model the Casimir effect, the Van der Waals force, diamagnetism, spontaneous parametric upconversion (its first major prediction) and a wide spectrum of explanations that are currently under development for other keys aspects of physics. Wikipedia has a begrudgingly tiny page dedicated to a rough outline of this theory:
Stochastic electrodynamics - Wikipedia
So it seems that quantum metaphysical mumbo jumbo is on the way out, and the halcyon days of scientific rationality and deterministic causality will soon be restored. Einstein would be delighted, but legions of would-be quantum mystics will soon be populating the bread lines.
But do not despair! Exciting things are happening behind the scenes that promise to unlock a dizzying spectrum of mind-bending new vistas of physical reality. For starters, we’ll soon find out if antimatter falls up or down in the Earth’s gravitational field – and if it falls up, a beautiful new theory will explain the dark matter and the dark energy effects in one fell blow. And yes, we’re talking about antigravity here ;
Also: a largely unsung theoretical physics genius named Itzhak Bars has elucidated a riveting new theory that describes our 4D universe as a “shadow” of a higher-dimensional 6D reality that possesses two perpendicular dimensions of time. He’s already derived general relativity and the standard model of physics from this beautiful new theory, which points the way to new insights into the nature (and malleability) of gravity, and resolves the problem of the hypothetical axion particle. It hasn’t caught on yet, but the powerful symmetries and elegance of his theory can’t remain ignored forever - the as-yet-unrealized potential of his model will lure in some ambitious brilliant theorists sooner or later. Then maybe we’ll achieve some real understanding of the most exotic paranormal events as the intersection of this higher-dimensional reality with the four dimensional world that we know and love.
