After the two sophons arrive on Earth, their first mission is to locate the high-energy particle accelerators used by humans for physics research and hide within them. At the level of science development on Earth, the basic method for exploring the deep structure of matter is to use accelerated high-energy particles to collide with target particles. After the target particles have been smashed, they analyze the results to try to find information reflecting the deep structure of matter. […] Successful collisions are very rare. […] This gives the sophon an opening. A sophon can take the place of a target particle and accept the collision. Because they are very intelligent, they can precisely determine through the quantum sensing formation the parts that the accelerated particles will follow within a very short period of time and move to the appropriate location. […] After a sophon is struck, it can deliberately give out wrong and chaotic results. Earth physicists will not be able to tell the correct result from the numerous erroneous results.
The three body problem, Cixin Liu
Or do they?
In the scenario imagined by the Chinese sci-fi author Cixin Liu, an advanced civilization on its way to conquer Earth sends two engineered 11-dimentional protons (“sophons“) to trick scientists and interfere with basic research. The idea is a quite clever one: to develop space travel and other high-tech marvels, humans have to understand the structure of matter first. If high-energy experimental particle physics is maimed at its core, no serious advance will be possible and when the two civilizations will meet, there’s going to be only one possible outcome. Sophons were programmed so that they take the place real proton-proton collisions and give random results, confusing the subsequent data analysis and physical interpretation.
Let’s assume that creating a sophon is actually possible. Do the laws of physics allow them to play this trick? To try answer this question, we have to understand first whether a sophon can predict the trajectory of another proton so that it can “catch” it as described in the novel. According to Heisenberg’s uncertainty principle, the precision to measure at the same time the momentum (let’s say the direction of motion) and the position is limited by the fact that subatomic particle can be described as matter waves:
Assuming for simplicity that the proton travels at the speed of light, and that the speed can be measured with a precision of 1%:
Substituting the numerical values, one can obtain an estimate of the uncertainty on the position which is about ten times larger than the size of the proton. This is just a back-on-the-envelope calculation, but it suggests that a sophon would have a hard time to trick the physicists, unless it can violate the uncertainty principle.
So is there an alternative to explain how it can accomplish this trick? In order to violate the Heisenberg principle, the sophon must have access to the so-called hidden variables. In a famous alternative interpretation of quantum mechanics due to David Bohm and Louis De Broglie (the pilot-wave theory), particles travel along directions determined by an exact function of position and momentum. The theory is deterministic and non-local, meaning that information must travel somehow faster than light, yielding what Einstein called spooky actions at distance.
So do the sophon have a chance to access information concerning the pilot-wave and predict the exact future position of the upcoming proton? You must ask this question to Aephraim Steimberg of University of Toronto, who observed in an experiment the non-local influence of another photon that the first photon had been entangled with (though Steinberg points out that both the standard interpretation of quantum mechanics and the De Broglie-Bohm interpretation are consistent with experimental evidence, and are mathematically equivalent).
To summarize: from a theoretical point of view, sophon can play the trick only if reality is non-local, quantum mechanics is incomplete and they can access information about the pilot-wave or some similar mechanism.
Pile-up events, to the rescue!
In the LHC, or any other similar accelerator, two beams of protons are accelerated while they travel along the ring. The beams consist of billion of protons, and they cross in four points (called interaction points) surrounded by the detectors ATLAS, CMS, Alice and LHCb. When they cross each other (bunch crossing), usually more than one proton-proton interaction happen during the same time frame (“event”). If we are lucky, only one interaction is really interesting (hard scattering), while the other represent a nasty background noise (pile-up events) we can get rid by measuring the tracks of charged particles and extrapolating them to the interaction point. The vertex where the highest-energy tracks converge is called primary vertex and is the source of the subsequent analyses.
My main objection to the sophon trick is thus that they must also assume that only one interaction per bunch crossing happen, while this is not true in general. How can a sophon be sure which interaction vertex will generate for example a Higgs boson or a pair of top quarks?
Also in this case, it’s a consequence of quantum mechanics that the outcome of an interaction is a superposition of possible different states and it cannot be predicted exactly before the observation is actually performed.
To summarize: even if we assume that a sophon can hit head-on an incoming proton and scramble the outgoing particles, it seems hard to believe that it would also able to predict which proton-proton interaction among many simultaneous other ones will give rise to interesting physics, while all the others will just generate background noise.
Sophons [reprised]: Is the Standard Model all there is?
One thing that confuses me about the scenario proposed by the author is the “random outcome” of the experiments. In fact, there is a serious theory which predicts such a scenario: the production of quantum black holes! According to this theory, if extra dimensions exist beyond the usual 3+1, gravity spreads across the “bulk”, explaining why this force appears to be so weak compared to the other known three forces. If the energy of the collision is high enough, a microscopic and very short-lived black hole can be produced. Eventually, such black holes are predicted to emit particles in an almost random way (“democratically“) according to a statistical distribution devised by Stephen Hawking. And no, their creation is not really a safety issue at CERN, even though someone in the past believed that the LHC was about to create a black hole which might have swallowed the Earth.
On the other hand, sophons may trick physicists in an even smarter and startling way: by presenting us results only compatible with our current theory, the so called Standard Model of particle physics! In such a scenario, we would be almost certain that there must be some unknown theory explaining a large number of experimental observations (dark matter, neutrino mass, or the accelerated rate of expansion of the universe just to name a few), but we would not be able to find out any experimental clue of this theory. We would be stuck forever in a theoretical rut, called the Standard Model…
Is this what’s happening right now? Is an alien civilization tricking us, hiding from us vital experimental results which would guide us towards a Theory of Everything?