A Physicist Responds to “The Three Body Problem” part 2

To start with, this post will be almost pure spoiler. I’m assuming, if you got through part 1, that you’ve read Cixin Liu’s book.

I’ve gotten partway through the second book in the trilogy myself, meaning that I’ve had some additional time to think about the contents of this post, but that I don’t know the ultimate outcome of the series.

This post is addressing a central conclusion of the first book, a major piece of science fiction that I didn’t address in the previous post because it is so intrinsic to the plot. This is about the idea of the Sophon induced ‘science lock-down.’ An alien race is going to invade the planet Earth in 400 years and this race is concerned that Human technology will advance in that time to be more powerful than the alien race’s own technology, so the aliens have played a trick to prevent humans from performing fundamental scientific research in order to prevent human technology from developing.

The key of this is the idea of the “Sophon.”As mentioned in the previous post, the word ‘proton’ was chosen over the name of an actual fundamental particle in order to facilitate a wordplay in Chinese… particularly the Chinese word that got translated into English as “Sophon.” This word was chosen from a modification of the word “Sophont.” As any science fiction aficionado can tell you, this word means “intelligent creature.” A Sophon is intended to be an intelligent proton, a robot the size and mass of a subatomic particle. These Sophons are capable to some extent of changing their size and shape and can communicate back to the aliens instantaneously. Sophons can also travel, as subatomic particles, at very nearly the speed of light.

You can see right from that paragraph the first place where the Sophon (and therefore the idea of science lock-down) are broken. Sophons communicate with the aliens instantaneously by means of quantum entanglement. If you’ve read anything else I’ve written, you know how I feel about the cliche of the ‘Ansible.’ Entanglement can’t be used to pass information: the Quantum mechanics doesn’t allow for this, no matter how you misinterpret it. Entanglement means correlation, not necessarily communication. This quantum mechanical effect is an interesting and very real phenomenon, but to understand what it actually means, you need to understand more about the rest of what quantum is… the story of ‘Three Body Problem’ never goes there. I won’t go there either except to suggest learning about the Bell Inequality.

The reason that Sophons are capable of producing science lock-down is because they can falsify data coming out of particle accelerators. Sophons can fly through the sensors in particle detectors and trigger them falsely, creating intelligently designed noise. At the surface, this is a horrible prospect, making it impossible for Humans to probe the deep structure of matter and therefore attain the understandings necessary to build Sophons ourselves. Do not pass go, no ‘correct’ results means no good science!

Obviously, this looks really bad. Very interesting science fiction idea. On the other hand, it also demands a bit of discussion, both about how particle accelerators work and on how science works.

Particle accelerators are the wrecking ball of the scientific enterprise. They generate data almost entirely by accelerating charged particles up to substantial fractions of the speed of light and slamming them into each other and into stationary targets. Particle physicists are all about impact cross sections and statistical probabilities of outcomes. The gold standard of a discovery in particle physics is a 5-sigma observation. ‘Sigma’ is, of course, standard deviation, which is a statistical standard by which scientists use the Gaussian statistical distribution to judge probability of occurrence –it’s the Bell Curve. Average is the peak of this curve, while one standard deviation is either one sigma to the left or right of average. Particle physics is set up around a simple statistical weight tabulation which can be couched as a question: “How likely is it that my observation is false/true?” If an event observed in the accelerator is spurious –that is, if the event is noise– the statistical machinery of particle physics places it close to the peak of the Bell Curve, that is at the average, which is to say that the event observed is ‘not different’ from noise. A 5-sigma event is an event which has been so well observed statistically that the difference from noise is five standard deviations from the peak of the Bell curve out into the tail (99.9999% of the curve’s area is captured within this extent of the tail!) This is essentially like saying that a conclusion is better than 99% certain to be NOT false.

Do you know how big a particle accelerator data set is? They include billions of events. Particle accelerators run for months to years on end, collecting data automatically 24 hours a day. And, the whole enterprise is based on the assumption that every observation independently might be a false outcome. Statistical weight determines the correctness of an observation. Physical theory exists to model both the trends and noise of an experiment.

As I said above, the purpose of the Sophons is to produce false results within the sensors of an accelerator’s detector apparatus. The most major detection devices in the modern systems are calorimeters and photomultipliers. Calorimeters simply detect heat deposition within the sensor volume while photomultipliers give a small current when they are perturbed by a passing electric charge. Usually, detector assemblies contain layers of sensors wrapped around the collision target where photomultipliers form multiple inner layers and calorimeters reside around the outside of the whole assembly. There are usually also magnetic fields applied through the detector so that charged particles will tend to follow curving paths as they pass outward through the different layers away from the collision site. There are other detector technologies and refinements of these ideas, but this gives a basic taste.

Here is the ALTAS detector at the Large Hadron Collider:


Using this layered design, photomultipliers can resolve the path of outward flying particles, determining their charges based upon their path curvature through the magnetic fields established by the solenoids and then the calorimeters determine how much energy was in the particle when that particle heats the calorimeter upon crashing into it. Certain particles types penetrate shields differently, necessitating layers of calorimeters with different structural characteristics in order to resolve different particle types. Computers correlate detection traces between the layers and tabulate what heat depositions relate to which flight paths. Particle physicists can then do simple arithmetic  to count up all the heats and all the charges on all the particles detected for one collision event and deduce which subatomic particles appeared during a particular collision. Momentum and energy/mass get conserved relativistically while charge is directly conserved and you simply add up what went in in order to account for what comes out during a collision.

In order to falsify data within such a detector, the smart subatomic particle, the Sophon, would need to fly back and forth through the detector layers, switching its charge polarity between passes and somehow dumping heat into calorimeters without being destroyed or lost in some way. How the Sophons get their kinetic energy is somewhat opaque in the story and I spent some time abortively rereading the TBP trying to figure this out, but it can be assumed that they possess a self-contained power supply which enables them to either recharge themselves from their surroundings, or simply dip into a long term battery reserve whenever they need it. They are clearly able to accelerate to highly relativistic velocities in a self-contained manner since they flew across the void from the alien homeworld to Earth, and then slowed down without external assistance at Earth. You could presume that they are able to write completely fake collision events into the detector, pretending to travel wrong velocities and masquerading as false charges and masses.

Now, like I said, this is terrible! The experiments can’t always give reliable results. Never mind that the real experiments must always be filtered for the fact that false results exist in the data set anyway.

In the paragraph above, I said “can’t always give reliable results” because the real data set of collision events still exists behind the fake data set. The Sophon flying back and forth can’t prevent real particle collisions from occurring and also interacting with the detector. The particle physicists would actually know right away that something isn’t right with the systematic structure of the experiment because they know how many particles are in their particle beams and also know the cross-sections of interaction, meaning that they start the experiment knowing statistically how many collision events to expect in a unit of time: Sophon interference with the experiment would only increase over the expected number. What you get is two overlapping data sets, one that is false and one that’s true. If the false data is much different from the true data, you inevitably bin them as distinct results because they would create a bimodal distribution to your data set… some measurements add up to five-sigma toward one result while a distinct set will ultimately add up as five-sigma toward something distinctly different. Then, you just let the theorists work out what’s what.

In the story, the scientists just throw up their hands and declare ‘sophon barrier’ saying that science ‘can’t advance’ because it can’t discern correctness.

This prospect has really kind of sat in the back of my mind, nagging me. I’m not completely certain that the author understands the overall scientific mindset or philosophy. Science starts out assuming that all results might be false! Having a falsehood layered on top of other potential falsehoods is really not that deterring to me, particularly since the scientists know the Sophon interference is present by the end of the story. Science as a process is intrinsically concerned with error checking and finding systematic interference, even intelligent fabrication of data within the scientific community –you think the Sophons are bad: somebody simply altering the data set as they see fit, completely independent of the experiment, is worse. And, we deal with this in reality! At least with the Sophons, a real data set must sit behind the mixture of false events. If the data set is merely bimodal or multimodal with statistics backing up each conclusion, you design experiments to address each… at some point, consistency of a result must ultimately dominate. Sorting out this noise would take time, but it would be unable to stop progress overall, especially since the scientists know the noise is present!

Now, giving false data is actually somewhat different than prohibiting data collection. This facet is somewhat unclear to me by the story –my memory fails. You can imagine that the Aliens realize that the humans know about the tampering and rather than leaving humans with a data set that contains some good data, they would simply have their Sophons swamp the detectors. In this, the Sophons fly back and forth within the detector giving so many false events that they prohibit the detector from being able to trigger for the resolution of real events. They could simply white us out!

While this would indeed be a bad thing, it would have a sort of a perverse effect on a real scientist. Consider: you know how fast your instrument triggers and you know the latency required for it to recover… this gives you a measure for how quickly and in what frequency the Sophon must act! You can just imagine the particle beam physicist salivating at the prospect of his Nobel prize in the nascent field of Sophon physics. Imagine the flood of grant proposals around the subject of baiting a Sophon into a particle beam line by the performance of basic science only to try to turn the particle beam against the Sophon in order to smash it apart and see how it works!

Really, if you were a high energy physicist and you knew unequivocally that a smart particle was flying around inside your instrument, how could you not be trying to figure out a way to probe it? It’s like getting Maxwell’s demon handed to you on a shiny platter!

A realistic outcome here is actually not the prohibition of science. It would be an arm-wrestling match with the Aliens: at the very best, leaving us with a partial data set that we can ultimately advance with, or giving us the chance to probe the Sophons directly.

The prospect of probing the Sophons directly contains the danger that it would be hard to distinguish engineered results from real ones, but every demonstration by the Sophons of some other confusing behavior is in fact data itself. The author made a huge argument in “Three Body Problem” that Sophons are typically point-like and would probably subscribe to the notion that they can’t be probed since they would essentially have no collision cross-section; I would resist this idea because it either violates or misunderstands quantum mechanics, which I detailed a bit in the previous post. The author might even suggest that Sophons can’t be probed because they can dodge collisions with other particles in the collider, but I would doubt that simply because of the inability for the Sophon to know things about other particles due to simple quantum mechanics and the affect of relativity altering the rates of information flow: the decision would need to be made very quickly and it would have a built in imprecision from Uncertainty! Moreover, the more time the Sophons spend performing confusing behavior in order to foil their own direct examination, the less time they can spend faking data in the experiments directed at basic research. As you may be aware, machines like the LHC are actually devoted to many lines of research simultaneously and physicists are remarkably adept at piggybacking one experiment on top of another in order to conserve resources and obtain additional bang for the same buck.

One final aspect of the “science lock-down” which I take some umbrage with is the notion that only particle accelerators are responsible for fundamental research. They aren’t. There is a huge branch of physics and chemistry probing quantum mechanics based on spectroscopy. Lasers are unequivocally a quantum mechanical device and much probing into basic quantum mechanics is performed by some variation on the theme of lasing. The Nobel prize winning discovery of the Bose-Einstein condensed matter phase did not occur in a super-collider, it occurred on an optical bench. Most super precise clock mechanisms used by the human race at this point are optical devices and have absolutely nothing to do with particle accelerators –optical gratings and optical metrology are driving the expansion of precision measurement! The leaps which are in the process of producing quantum computers (one device the author specifically prohibits in book 2 under the science lockdown!) are not being made at particle accelerators at all: they are being made in optical lattice traps on lab benches and in photo-etched masks used to produce nano-scale solid state resonators. We are currently in the process of building analog quantum computers for the purposes of simulating quantum chromodynamic systems using optical and nano-resonator devices… and this development has nothing to do with particle accelerators, except as a means of reproducing results! The author made the argument that humans couldn’t build massive super-collider accelerators, Synchrotrons and Linacs, fast enough to match the production capacity that the Aliens have for making the sophons needed to foil these instruments, but the author never even touched on the rapidly expanding field of plasma wake field acceleration, which uses lasers to accelerate particles to relativitistic speeds in bench-top apparatuses for a fraction of the price of a super-collider.

The bleeding edge of physics is very multi-pronged; the Higgs boson discovery carried out in a synchrotron may someday be reproduced by a bench-top plasma wake field accelerator for a tiny fraction of the price. Can ‘locking down’ big particle accelerators like the LHC prohibit the extensive physical exploration that is occurring due to a mostly unrelated black swan technological development like lasers? I really don’t think it can. Tying one arm behind your back leaves you with the other arm. It’s true that the mothballing of the superconducting super-collider in the United States prevented humans from definitively discovering the Higgs boson for more than a decade, but that isn’t to say that there aren’t other avenues to the same discovery.

Do I think that science lockdown is possible by the means suggested by the author? Not really. And, especially not for devices like quantum computers, which is one critical development that the author suggests is prohibited by sophon interference in the second book.

Don’t get me wrong, this is a good piece of science fiction and it’s a wonderful thought experiment, but like many thought experiments, it’s arguable.

edit 2-16-17

I saw a physics colloquium yesterday delivered by a Nobel prize winner. His lab is currently working on a molecular spectroscopy experiment directed at measuring the electric dipole moment of the electron. A precision measurement of this value ties directly to the existence (or not) of supersymmetric particle theory… which is one candidate expansion of the Standard Model of particle physics. This experiment is not being done in a super collider, but on an optics bench for a fraction of the price. Experiments like this one completely invalidate the thesis of Three Body Problem: that by locking down colliders that there is no other way for particle physics to advance. There are other ways that are comparatively cheap and requiring less resources and manpower. Physics would find a way.