The title of this post is the same as that of an article in Scientific American by Tam Hunt. Hunt has been a fan of electromagnetic theories of consciousness and this article is certainly in line with that view. Hunt makes some interesting claims in the article I would like to discuss. The claim has to do with ephaptic field effects.
Another team compared the speed of ephaptic field effects in various tissues, finding that the speed of propagation of ephaptic fields in gray matter is about 5,000 times faster than neural firing.
This means that what would take normal spike pathways one second to span through the brain, could be traversed 5,000 times during that same time interval with ephaptic effects. If we cube this over the volume of the brain we get an information density up to a staggering 125 billion times more from ephaptic fields than from synaptic firing.
Here’s the problem I have with this claim. In this same article, Hunt discusses a 2019 paper: Slow periodic activity in the longitudinal hippocampal slice can self-propagate non-synaptically by a mechanism consistent with ephaptic coupling. I’ve read this paper before and it demonstrates that an EM field generated by a neuron can activate nearby neurons up to a distance of 400 microns. The study may prove that the EM field can propagate activity to nearby neurons at a very fast rate, but that doesn’t mean a signal could be passed across the entire brain passing through different functional boundaries at the same rate. For that to be possible, each neuron across the brain would have to activate some kind of ionic activity in the dendrites, soma, or axion of other neurons in order to continue the propagation of the signal. What’s more the strength of activity would need to be strong enough to cause other neurons to activate and to pass the signal to other neurons. Not only would the generation of ionic activity require additional time, but also the signal could fade away or become distorted as soon as any gaps appeared in the propagation.
It’s seems misleading at best to suggest neurons using EM fields could be propagating signals across the entire brain at a 0.0002 millisecond rate. However, it certainly might be possible that propagation could occur more quickly that synaptic transmission, but only in relatively small parts of the brain. This could be part of the mechanism that produces the traveling waves that move in the familiar alpha, beta, delta, theta, and gamma bands.
That the laws of physics are computable seems to be an article of faith among some. If the laws of physics are computable, then the brain (and consciousness) would be computable unless we are willing to entertain supernatural exemptions from the laws. The computability of reality, however, is actually a conjecture. It certainly can’t be proven because we can never be sure we might come up with physical phenomena that could never be computed.
We have good reason to suspect that the conjecture is false. There is the fermion problem in the Standard Model that I’ve discussed previously. There are also the problem of computation with many-body problems in condensed matter physics. A particular case of the many-body problem called the “spectral gap problem” seems to demonstrate that at least one physical phenomena cannot be computed.
Interestingly, recent work in condensed matter quantum physics indicates that—possibly—quantum many-body systems could infringe the Total thesis. In 2012, Eisert, Müller and Gogolin established the surprising result that
the very natural physical problem of determining whether certain outcome sequences cannot occur in repeated quantum measurements is undecidable, even though the same problem for classical measurements is readily decidable. (Eisert, Müller & Gogolin 2012: 260501.1)
This was a curtain-raiser to a series of dramatic results about the uncomputability of quantum phase transitions, by Cubitt and his group (Cubitt, Perez-Garcia, & Wolf 2015; Bausch, Cubitt, Lucia, & Perez-Garcia 2020; Bausch, Cubitt, & Watson 2021). These results concern the “spectral gap”, an important determinant of the properties of a substance. A quantum many-body system is said to be “gapped” if the system has a well-defined next least energy-level above the system’s ground energy-level, and is said to be “gapless” otherwise (i.e., if the energy spectrum is continuous). The “spectral gap problem” is the problem of determining whether a given many-body system is gapped or gapless.
The uncomputability results of Cubitt et al. stem from their discovery that the halting problem can be encoded in the spectral gap problem. Deciding whether a model system of the type they have studied is gapped or gapless, given a description of the local interactions, is “at least as hard as solving the Halting Problem”
There is a great account of the development of the Cubitt et al proof written by the researchers themselves in a Scientific American article called the “The Unsolvable Problem.”
If the laws of physics are not completely computable, then the question of whether the brain is computable becomes an empirical question.
Is there empirical evidence that suggests activity in the brain that is not Turing computable?
I think the answer is yes.
Cognition seems to be accompanied by synchronous firings of groups of neurons sometime in distant parts of the brain. There is evidence some of this is generated from a form of communication that is not mediated by chemicals or physical connections and goes under the general term of “ephaptic coupling.”
In the present study, we show that slow periodic activity in the longitudinal hippocampal slice is a self-regenerating wave which can propagate with and without chemical or electrical synaptic transmission at the same speeds. We also show that applying local extracellular electric fields can modulate or even block the propagation of this wave in both in silico and in vitro models. Our results support the notion that ephaptic coupling plays a significant role in the propagation of the slow hippocampal periodic activity. Moreover, these results indicate that a neural network can give rise to sustained self-propagating waves by ephaptic coupling, suggesting a novel propagation mechanism for neural activity under normal physiological conditions.
Travelling waves propagate in different directions during separate cognitive processes. In episodic memory, travelling waves tended to propagate in a posterior-to-anterior direction during successful memory encoding and in an anterior-to-posterior direction during recall. Because travelling waves of oscillations correspond to local neuronal spiking, these patterns indicate that rhythmic pulses of activity move across the brain in different directions for separate behaviors.
The traveling waves – think of a stadium wave – have an uncanny resemblance to turbulence. They began to appear in the conscious brain on waking and mostly vanish during sleep and unconsciousness.
Furthermore, we build a whole-brain model with coupled oscillators to demonstrate that the best fit to the data corresponds to a region of maximally developed turbulent-like dynamics, which also corresponds to maximal sensitivity to the processing of external stimulations (information capability). The model shows the economy of anatomy by following the exponential distance rule of anatomical connections as a cost-of-wiring principle. This establishes a firm link between turbulent-like brain activity and optimal brain function.
The brain consists of connections of neurons called the connectome. The number of neurons, of course, varies by species. The C. elegans brain has a few more than a hundred. The human brain has around 85 million in total with about 16 billion in the cortex. Undoubtedly communication of information in either brain is largely through the connectome. The connectome might explain completely the operation of the C. elegans brain. In that sense, its brain might be computable. The human brain on the other hand seems to have supra-connectome properties. Turbulent, wave-like, and vortical activity arise as emergent properties as a function of the complexity, size, and structure of the connectome. This activity has causal force since it produces real neural firings that might not be predictable from the connectome itself.
A supra-connectome might be the evolutionary solution for communicating tightly coupled data across a fragmented and asynchronous brain. By tightly coupled data, I mean data that couldn’t be broken into chunks without losing meaning. For example, this paragraph could be broken into words but, if the words arrive in pieces and at different times, it might be impossible to reassemble the paragraph and understand its meaning. Turbulent activity in the brain may have arisen evolutionarily as a side effect of size and been detrimental. Rather than eliminating it, however, evolution might have learn to control it through a critical balance between excitatory and inhibitory pressures and to use it as an information transmission mechanism over and above the connectome itself.
A white elephant is a possession that its owner cannot dispose of without extreme difficulty, and whose cost, particularly that of maintenance, is out of proportion to its usefulness. – Wikipedia
SpaceX is scheduled for another try at launching its giant rocket in June. Will it work this time? By work, I mean both booster and Starship vehicle return to the ground more or less intact Each launch has done better than the previous but all three launches have experienced “disassemblies” of both its booster and its main vehicle.
This will be the fourth test in a year. Some people reckon it may need twenty launches before it is ready for its first commercial cargo and even more launches before it is ready for a crew.
It’s years behind its promised schedule.
Its design is revolutionary and promises to make reaching Earth orbit cheap and easy. It’s fueled by liquid methane and liquid oxygen. The booster and the Starship vehicle are intended to be fully reusable. Both bodies are composed of stainless steel cylinders, each with a height less than six feet, and walls less than a quarter inch thick that have been welded together. When I think of those quarter inch walled cylinders welded together, I can’t help but think of the Titan submersible. How many heatings and coolings, jarring launches and landings before something pops? I hope they have tested this some way.
Elon Musk has promised a lot from the system. He considers it to be a kind of all purpose workhorse not only for interplanetary travel but even for quick travel from point to point on Earth. The U.S. military is even looking into whether it could be used to transport troops. It is critical to Musk’s plan to colonize Mars.
I’m not a fan of Elon Musk but I am a fan of SpaceX, so I think this would be great if Starship works. And maybe it will. I doubt this is going to fulfill Musk’s dreams of interplanetary travel or much of anything else besides lifting some heavy stuff into low Earth orbit.
Do we really think business travelers are going to hop a Starship to reach Tokyo in an hour? Is there going to be another booster waiting there for the return flight? What about weather? Can it launch in rain or with a little bit of wind? Probably not. The next generation of supersonic transport is going to fill this need. An SST might need a few extra hours to get there, but it will probably be a lot cheaper and more reliable than a giant rocket. A little bit of wind isn’t going to ground it. Even if it lacks the cachet of space flight, I think I’ll take the SST.
What about space flight? The problem is that Starship has been designed as a sort of Swiss Army knife of space transport. A Swiss Army knife can be a great tool in a pinch for some things. But it is not a hammer or even a saw unless whatever you need to slice is fairly skinny.
What really is needed for interplanetary exploration are different types of special purpose vehicles that can work together, not one single massive rocket.
1- Boosters that can lift really large and heavy objects from Earth to orbit.
The Starship booster could succeed at doing this, but the Starship vehicle isn’t needed because most of this stuff isn’t coming back. This will be things destined for Earth orbit or hauled to the Moon or Mars.
2- Transports for equipment, supplies, and people between Earth and the Moon or Mars.
These needs to be big and fast, but they don’t need to return to Earth or land anywhere else. They can be constructed in orbit, but they will need to use an advanced propulsion system, such as an ion drive, that can shorten the travel times. An ion drive is under development by NASA that could reach Mars in two months.For interplanetary travel a transport will need heavy shielding to protect humans from galactic cosmic rays.
3- Landers for non-human cargo.
Landing on Mars, landing on the Moon, and returning to Earth have different requirements. A lander carrying equipment and supplies doesn’t need to be able to return to space. No need for a Starship rocket carrying equipment to Mars to blast off after arrival.These could be cheap and able to be carried by the transports from Earth orbit to their final destination. Ideally the landers themselves could be repurposed once their cargo is removed. No need for complex or heavy life support systems for humans on these.
4- Space planes for humans to return to Earth.
The Space Shuttle had the right idea for return to Earth. Sierra Space is developing the Dream Chaser space plane. We can fly or glide like a plane in the Earth’s atmosphere. Why not take advantage of it?Why build a return vehicle with a big engine that it can land upright like Starship? It’s pointless on Earth where a lighter or even jet-fueled plane can serve. A plane could potentially land on almost any runway in a pinch.
5- Landers for humans for Mars and the Moon.
These need to be able to refuel and takeoff again without an additional boosters after landing. NASA is expecting the Starship vehicle to land on the Moon. Maybe it will some day. But since we are only carrying humans and life support, the Starship may be overbuilt unless we are planning to be transporting hundreds of people. I don’t see that anytime soon.
Where does the Starship system fit into this? The booster will be wonderful when we need to launch heavy stuff. There will always be that need, but ideally we would want to move to a miniaturization approach with most satellites and exploration vehicles.The Starship vehicle might work as human landers on the Moon or Mars, but probably vehicles specifically designed for the task might serve better.
Bottomline is I don’t see the future Musk sees, but then I’m not a visionary.
Broad Speculations 
