## Tuesday, February 19, 2008

### How to disprove spoon bending

The video above is wrong, as you will see below. :-) The video is an example of situations where you should discard observations done by a nervous Colombian skeptic pretending to be a charlatan and insist on your theory or more precisely a theory of others, QED.

After some time, Sean Carroll wrote an article that I enjoyed and that I completely subscribe to. His aim is to explain that the limits of science don't mean that it is reasonable to expect the discovery of new phenomena such as telekinesis.

He begins by explaining several principles of science:

• Science never proves anything rigorously. Instead, it is constructing a framework that allows us to say that certain things are very plausible while others are less plausible or almost implausible. For example, it allowed Feynman to say that it is much more likely for UFOs to be explained by the known irrational characteristics of terrestrial beings rather than by any unknown rational efforts of extraterrestrial beings. ;-)
• Every good theory not only describes some phenomena but it also descibes the range of its validity. It tells us what special things we have to do in order to "take it to the limits" where the theory may break down. Inside the mantinels, it is very implausible that we don't understand what's going on.
• A theory can't be universally proven to be right but it can in principle be proven wrong but such a falsification is only conceivable outside the limits where the theory hasn't yet been tested. As Feynman said, we can never be sure that we are right; we can only be sure when we are wrong.

Concerning telekinesis, the scientific strategy to (almost) prove that it is impossible is based on the following steps:

Spoons are composed of known matter

Electrons, up-quarks, down-quarks, gluons, and photons are everything you need. If a new particle were relevant for spoon bending, it would have to be either light enough and strongly enough interacting (but then we would have already known it) or heavy enough or too weakly interacting (but then it couldn't be relevant in the spoon bending setup).

There is no middle ground here. If something is very visible, it is inevitably well-known, and if something is not known, then it cannot have too visible and far-reaching consequences. The only loophole would be to find something really special about spoons and brains that allows the laws that were determined using other objects to break down. It seems very unlikely that spoons and brains are such special objects.

Matter interacts through forces

One must also defend the viewpoint that all phenomena in Nature that we have observed as of 2008 can be described by an effective field theory that can be interpreted, in laywoman's terms, as a system of laws describing forces that influence particles. In quantum field theory, forces may be described as the exchange of virtual bosons.

No behavior of physical systems that would require something more than particles and forces for its explanation (at least an approximate one) has been empirically observed so far and it is thus likely that spoons and brains cannot be exceptions either.

Phenomena are controlled by electromagnetism

Using the language of quantum field theory, we only know four forces: electromagnetism, gravity, strong force, weak force. The strong and weak nuclear forces are finite-range forces (among color-neutral objects) and cannot be used to transfer influence from the brain to the spoon because the distance is too long. Gravity is too weak because brains and spoons are too light.

Electromagnetism is the last candidate but we know that Maxwell's equations don't allow us to bend spoons unless the brain is capable to produce extremely strong electromagnetic fields which has so far been falsified by all experiments.

There can exist additional forces - and indeed, there exist infinitely many of them according to string theory - but once again, we know that they must either be too weak, too short-range, or they must have some other reasons why we haven't yet observed them i.e. why we don't need them to explain the experiments that have been successully explained. The same reason implies that these new forces will probably be irrelevant for the spoon bending experiment, too.

You can't make a new phenomenon relevant and irrelevant at the same moment.

Generalizing rational thinking beyond spoon bending

Needless to say, similar reasoning - combined with a detailed analysis of the situation according to the known laws - can be applied to any kind of paranormal phenomena, including Sean Carroll's paranormal influence of cosmological evolution on broken eggs (in his ESP picture, cosmology has a secret power that protects broken eggs from unbreaking).

In all cases, we can show that a vast set of situations has been successfully explained with the known concepts of physics and because the hypothetical paranormal situations seem qualitatively identical to those that have been measured and explained, it is likely that they must follow the same laws.

Known limits of theories

Finally, I want to describe what kinds of limitations various known scientific theories have.

First, there exist a lot of approximate, rough theories. Various quantities are claimed or believed to be proportional to each other - or linear functions of each other. Virtually every continuous relationship between several quantities can be simplified to a linear law if all the quantities only change by a little bit: this simplification is referred to as linearization. Once the quantities deviate much more, the errors grow and the linearized law starts to break down.

The more messy scientific discipline you deal with, the closer the limits of its theories are.

However, in theoretical physics, we usually deal with theories that are much more universal and whose limits are much further, usually well beyond the circumstances that can be realized in everyday life. Many people misunderstand it which is why I find it important to say that the theories we work with are "theories of almost everything", indeed.

Nevertheless, even theoretical physicists have used - and are still using - a lot of theories that are currently understood to be approximate theories only; string theory is the only known theory that gives us reasons to think that it must be completely accurate and cannot be an approximation of another theory. On the other hand, the old-fashioned, approximate theories break down once you reach certain limits:

• Limit on speed: non-relativistic mechanics as written down by Isaac Newton is known to be extremely accurate for all engineering applications but the errors start to increase if the velocities approach the speed of light. On the other hand, if all the speeds are "much" smaller than the speed of light, the errors of non-relativistic theories will be "very" small. One can quantify the words "much" and "very": the speed of light "c" plays a crucial role in the formulae relating the speeds and the errors of Newton's theory.
• Limits on mass, temperature, pressure, density of macroscopic objects: when we describe various macroscopic objects, approximate laws of certain kinds can break down if the mass exceeds a certain limit. For example, too heavy a star may start to require the effects of general relativity to be taken into account - but these effects can be neglected if the mass is low enough: the quantitative value of the limit involves Newton's constant "G". Various state equations for gases, liquids, and solids break down if temperature, pressure, or density is taken away from certain limits - for example, if you cross the line of a phase transition. There are too many examples of these limits - they constrain a huge number of effective, non-universal laws - which is why I can't tell you a universal constant that controls all of them.
• Microscopic limits on distance and time: certain laws only hold if the distances between particles are long enough and if we study them at long enough time scales. At shorter distances or time scales, new effects of quantum mechanics or effects of more accurate theories that go beyond effective field theories may start to be important. Quantum mechanics starts to be important when the angular momentum, action, and other quantities of the right dimension start to approach (or drop below) Planck's universal constant "h". New physics of quantum field theories starts to matter if you drop below their characteristic distance scales. The organization of our knowledge according to the distance scale - we are learning about the architecture of matter at ever smaller distance scales - is the main principle of the effective field theory approach to physics and the renormalization group, concepts that many physicists consider to be the most important insights of the last 40 years in physics.
• Limits on energy, momentum, and "temperature" of particles: certain laws only hold if the energy of the particles that participate in the process is smaller than a certain bound (usually only given approximately). Quantum mechanics links energy and frequency which means that "too high energy" is actually equivalent to "too high frequency" i.e. "too short time intervals" and the limits in this paragraph are therefore pretty much equivalent to those in the previous paragraph. The same comment applies to temperature because temperature is nothing else than the energy per one degree of freedom.
• Strong coupling: we have already mentioned the example of a heavy star for which general relativity starts to matter. More generally, various theories in physics have "coupling constants" that generalize Newton's constant. If these constants are much smaller than one (or another characteristic value), we can use a certain linearization. If they are greater than one, these laws usually break down and physical phenomena may become qualitatively different. In other words, certain conclusions derived with the assumption of weak coupling don't generalize to strong coupling.
• Many is different: this is a favorite comment by advocates of "emergent phenomena". In reality, most of the laws we know apply to large ensembles of particles much like small ensembles of particles and we can show that no genuinely new phenomena can occur. On the other hand, there exist theoretical calculations that break down when the integer-valued number of certain objects is too high. For example, if you consider quantum chromodynamics with quarks that can have too many colors N, the conclusions extracted from a theory with a small N can break down even qualitatively: for example, new dimensions of space can be born (holography). In this particular case and related cases, the so-called 't Hooft coupling is a coupling constant that is proportional to N which is why this paragraph is reduced to the previous paragraph about the strong coupling.

We have seen some important examples of known theories. If you take the theories to the limits, they may start to give you wrong predictions. But if you stay within the mantinels - and I am convinced that all spoon benders do - the known theories almost certainly apply; they make spoon bending impossible.

Equally importantly, there exist limits on unknown phenomena. Unknown phenomena may exist but because we have not yet seen them (at least not clearly enough) and the theories assuming that the new phenomena don't exist work pretty well, they must correspond to particles that are either too heavy or new forces that are too weak or new forces that make the production of new particles too unlikely. Or the new physical objects and effects must emulate the old ones very faithfully.

Such new things may exist and indeed, many physicists like to think about them and do think about them. But on the other hand, the fact that we haven't yet clearly observed them makes it very unlikely that they are too relevant for situations that look too similar to the experiments that have been done or situations that look even simpler.

It is usually hard to learn new things about a hard science

In real physics, it usually takes a very powerful collider with a very high energy per particle that can probe the architecture of matter at very short distances and very short time scales. Your accelerator needs a high enough luminosity - a high flux of the new particles - so that even processes that have a low probability (or cross section) have a reasonable chance to occur at all (or quickly enough). Then you need detectors and other instruments that measure some quantities accurately enough and you also need high enough amounts of money for the apparata and for the physicists to analyze the experiments and possible theories explaining them seriously and professionally enough. ;-)

These things seem to require a lot of efforts, time, and money, and there are good reasons why it is so. It is plausible that there can exist completely new limitations of our existing theories that we are not aware of and that are very different from the list above. I am very curious what they could be but I expect that over 99% of the proposals about their identity are going to be bogus.

There can also exist completely new strategies how to get the new information about the new particles and forces that act at higher energies more cheaply or more accurately but once again, I doubt that most suggestions regarding these strategies will make too much sense. Hard science is usually hard: that's why it's called a hard science.

And that's the memo.

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