Monday, August 13, 2018

Search for ETs is more speculative than modern theoretical physics

Edwin has pointed out a new tirade against theoretical physics,
Theoretical Physics Is Pointless without Experimental Tests,
that Abraham Loeb published at pages of Scientific American which used to be an OK journal some 20 years ago. The title itself seems plagiarized from Deutsche or Aryan Physics – which may be considered ironic for Loeb who was born in Israel. And in fact, like his German role models, Loeb indeed tries to mock Einstein as well – and blame his mistakes on the usage of thought experiments:
Einstein made great discoveries based on pure thought, but he also made mistakes. Only experiment and observation could determine which was which.

Albert Einstein is admired for pioneering the use of thought experiments as a tool for unraveling the truth about the physical reality. But we should keep in mind that he was wrong about the fundamental nature of quantum mechanics as well as the existence of gravitational waves and black holes...
Loeb has a small, unimportant plus for acknowledging that Einstein was wrong on quantum mechanics. However, as an argument against theoretical physics based on thought experiments and on the emphasis on the patient and careful mental work in general, the sentences above are at most demagogic.

The fact that Einstein was wrong about quantum mechanics, gravitational waves, or black holes don't imply anything wrong about the usage of thought experiments and other parts of modern physics. There's just no way to credibly show such an implication. Other theorists have used better thought experiments, have thought about them more carefully, and some of them have correctly figured out that quantum mechanics had to be right and gravitational waves and black holes had to exist.

The true fathers of quantum mechanics, especially Werner Heisenberg, were really using Einstein's new approach based on thought experiments, principles, and just like Einstein, they carefully tried to remove the assumptions about physics that couldn't have been operationally established (such as the absolute simultaneity killed by special relativity; and the objective existence of values of observables before an observation, killed by quantum mechanics).

Note that gravitational waves as well as black holes were detected many decades after their theoretical discovery. The theoretical discoveries almost directly followed from Einstein's equations. So Einstein's mistakes meant that he didn't trust (his) theory enough. It surely doesn't mean and cannot mean that Einstein trusted theories and theoretical methods too much. Because Loeb has made this wrong conclusion, it's quite some strong evidence in favor of a defect in Loeb's central processing unit.

The title may be interpreted in a way that makes sense. Experiments surely matter in science. But everything else that Loeb is saying is just wrong and illogical. In particular, Loeb wrote this bizarre paragraph about Galileo and timing:
Similar to the way physicians are obliged to take the Hippocratic Oath, physicists should take a “Galilean Oath,” in which they agree to gauge the value of theoretical conjectures in physics based on how well they are tested by experiments within their lifetime.
Well, I don't know how I could judge theories according to experiments that will be done after I die, after my lifetime. That's clearly impossible so this restriction is vacuous. On the other hand, is it OK to judge theories according to experiments that were done before our lifetimes or before physicists' careers?

You bet. Experimental or empirical facts that have been known for a long time are still experimental or empirical facts. In most cases, they may be repeated today, too. People often don't bother to repeat experiments that re-establish well-established truths. But these old empirical facts are still crucial for the work of every theorist. They are sufficient to determine lots of theoretical principles.

You know, it's correct to say that science is a dialogue between the scientist and Nature. But this is only true in the long run. It doesn't mean that every day or every year, both of them have to speak. If Nature doesn't want to speak, She has the right to stay silent. And She often stays silent even if you complained that She doesn't have the right. She ignores your restrictions on Her rights! So at the LHC after the Higgs boson discovery, Nature chose to remain silent so far – or She kept on saying "the Standard Model will look fine to you, human germ".

You can't change this fact by some wishful thinking about "dialogues". Theorists just didn't get new post-Higgs data from the LHC because so far, there are no new data at the LHC. They need to keep on working which makes it obvious that they have to use older facts and new theoretical relationships between them, new hypotheses etc. In the absence of new theoretical data, it is obvious that theorists' work has to be overwhelmingly theoretical or, in Loeb's jargon, it has to be a monologue! When Nature has something new and interesting to say (through experiments), Nature will say it. But theorists can't be silent or "doing nothing" just because Nature is silent these years! Only a complete idiot may fail to realize these points or agree with Loeb.

What Loeb actually wants to say is that a theorist should be obliged to plan the experiments that will settle all his theoretical ideas within his lifetime. But that's not possible. The whole point of scientific research in physics is to study questions about the laws of Nature that haven't been answered yet. And because they haven't been answered yet, people don't know and can't know what the answer will be – and even when it will be found.

An experimenter (or a boss or a manager of an experimental team) may try to plan what the experiment will do, when it will do these things, and what are the answers that it could provide us with. Even this planning sometimes goes wrong, there are delays etc. But this is not the main problem here. The real problem is that the result of a particular experiment is almost never the real question that people want to be answered. An experiment is often just a step towards adjusting our opinions about a question – and whether this step is a big or small one depends on what the experimental outcome actually is, and this is not known in advance.

Loeb has mentioned examples of such questions himself. People actually wanted to know whether there were black holes and gravitational waves. But a fixed experiment with a fixed budget, predetermined sensitivity etc. simply cannot be guaranteed to produce the answer. That's the crucial point that kills Loeb's Aryan Physics as a proposed (not so) new method to do science.

For example, both gravitational waves and black holes are rather hard to see. Similarly, the numerical value of the cosmological constant (or vacuum energy density) is very small. It's this smallness that has implied that one needed a long – and impossible to plan – period of time to discover these things experimentally.

Because black holes, gravitational waves, and a positive cosmological constant needed fine gadgets – and it was not known in advance how fine they had to be – does it mean that the theorists should be banned from studying these questions and concepts? The correct answer is obviously No – while Loeb's answer is Yes. Almost all of theoretical physics is composed of such questions. We just can't know in advance how much time will be needed to settle the questions we care about (and, as Edwin emphasized, there is nothing special about the timescale given by "our lifespan"). We can't know what the answers will be. We can't know whether the evidence that settles these questions will be theoretical in character, dependent on somewhat new experimental tools, or dependent on completely new experimental tools, discoveries, and inventions.

None of these things about the future flow of evidence can be known now (otherwise we could settle all these things now!) which is why it's impossible for these unknown answers to influence what theorists study now! The influences that Loeb demands would violate causality. If the theorists knew in advance when the answer is obtained, they would really have to know what the answer is – as I mentioned above, the confirmation of a null hypothesis always means that the answer to the interesting qualitative question was postponed. But then the whole research would be pointless.

So if science followed Loeb's Aryan Physics principles, it would be pointless! The real science follows the scientific method. Scientists must make decisions and conclusions, often conclusions blurred by some uncertainty, right now, based on the facts that are already known right now – not according to some 4-year plans, 5-year plans, or 50-year plans. And if their research depends on some assumptions, they have to articulate them and go through the possibilities (ideally all of them).

It's also utterly demagogic for him to talk about the "Galilean Oath" because Galileo Galilei disagreed with ideas that were very similar to Loeb's. In particular, Galileo has never avoided the formulation of hypotheses that could have needed a long time to be settled. One example where he was wrong was Galileo's belief that comets were atmospheric phenomena. That belief looks rather silly to me (didn't they already observe the periodicity of some comets, by the way?) but the knowledge was very different then. Science needed a long time to really settle the question.

But more generally, Galileo did invent lots of conjectures and hypotheses because those were the real new concepts that became widespread once he started the new method, the scientific method. Google search for "Galileo conjectured" or "Galileo hypothesized". Of course you get lots of hits.

As e.g. Feynman said in his simple description of the scientific method, the scientific method to search for new laws works as follows: First, we guess the laws. Then we compute consequences. And then we compare the consequences to the empirical data.

Note the order of the steps: the guess must be at the very beginning, scientists must be free to present all such possible hypotheses and guesses, and the computation of the consequences must still be close to the beginning. Loeb proposes something entirely different. He wants some planning of future experiments to be placed at the beginning, and this planning should restrict what the physicists are allowed to think about in the first place.

Sorry, that wouldn't be science and it couldn't have produced interesting results, at least not systematically. And these restrictions are indeed completely analogous to the bogus restrictions that the church officials – and later various philosophers etc. – tried to place on the scientific research. Like Loeb, the church hierarchy also wanted the evidence to be direct at all cases. But one of the ingenious insights by Galileo was that he realized that the evidence may often be indirect or very indirect but one may still learn a great deal of insights out of it.

The simplest example of this "direct vs indirect" controversy are the telescopes. Galileo has improved the telescope technology and made numerous new observations – such as those of the Jovian moons. The church hierarchy actually disputed that those satellites existed because the observation by telescopes wasn't direct enough for them. It took many years before people realized how incredibly idiotic such an argument was. It would be a straight denial of the evidence. The telescopes really see the same thing as the eyes when both see something. Sometimes, telescopes see more details than the eyes – so they must be considered nothing else than improved eyes. The observations from eyes and telescopes are equally trustworthy. But telescopes have a better resolution.

The laymen trust telescopes today even though the telescope observations are "indirect" ways to see something. But the tools to observe and deduce things in physics have become vastly more indirect than they were in Galileo's lifetime. And most laymen – including folks like Loeb – simply get lost in the long chains of reasoning. That's one reason why many people distrust science. Because they haven't verified them individually (and most laymen wouldn't be smart or patient enough to do so), they believe that the long chains of reasoning and evidence just cannot work. But they do work and they are getting longer.

The importance of reasoning and theory-based generalizations was increasing much more quickly during Newton's lifetime – and it kept on increasing at an accelerating rate. Newton united the celestial and terrestrial gravity, among other things. The falling apple and the orbiting Moon move because of the very same force that he described by a single formula. Did he have a "direct proof" that the apple is doing the same thing in the Earth's gravitational field as the Moon? Well, you can't really have a direct proof of such a statement – which could be described as a metaphor by some. His theory was natural enough and compatible with the available tests. Some of these tests were quantitative yet not guaranteed at the beginning. So of course they increased the probability that the unification of celestial and terrestrial gravity was right. But whether such confirmations would arise, how strong and numerous they would be, and when they would materialize just isn't know at the beginning.
The risk for physics stems primarily from mathematically beautiful “truths,” such as string theory, accepted prematurely for decades as a description of reality just because of their elegance.
OK, this criticism of "elegance" is mostly a misinterpretation of pop science. Scientists sometimes describe their feelings – how their brains feel nicely when things fit together. Sometimes they only talk about these emotional things in order to find some common ground with a journalist or another layman. But at the end, this type of beauty or elegance is very different from the beauty or elegance experienced by the laymen or artists. The theoretical physicists' version of beauty or elegance reflects some rather technical properties of the theories and the statement that these traits increase the probability that the theory is right may be pretty much proven.

But even if you disagree with these proofs, it doesn't matter because the scientific papers simply don't use the beauty or elegance arguments prominently. When you read a new paper about some string dualities, string vacua, or anything of the sort, you don't really read "this would be beautiful, and therefore the value of some quantity is XY". Only when there are some calculations of XY, the authors claim that there is some evidence. Otherwise they call their propositions conjectures or hypotheses. And sometimes they use these words that remind us of the uncertainty even when there is a rather substantial amount of evidence available, too.

But the uncertainty is unavoidable in science. A person who feels sick whenever there is some uncertainty just cannot be a scientist. Despite the uncertainty, a scientist has to determine what seems more likely and less likely right now. When some things look very likely, they may be accepted as facts at a preliminary basis. Some other people's belief in these propositions may be weaker – and they may claim that the proposition was accepted prematurely. But at the end, some preliminary conclusions are being made about many things. Science just couldn't possibly work without them.

By the way, I forgot to discuss the subtitle of Loeb's article:
Our discipline is a dialogue with nature, not a monologue, as some theorists would prefer to believe
Note that he emphasizes that theoretical physics is "his discipline". It sounds similar to Smolin's fraudulent claims that he was a "string theorist". Smolin isn't a string theorist and doesn't have the intellectual abilities to ever become a string theorist. Whether Loeb is a theoretical physicist is at least debatable. He's the boss of Harvard's astronomy department. The words "astrophysicist" would surely be defensible. But the phrase "theoretical physicist" isn't quite the same thing. I hope that you remember Sheldon Cooper's explanation of the difference between a rocket scientist and a theoretical physicist.

Why doesn't Missy just tell them that Sheldon is a toll taker at the Golden Gate Bridge? ;-)

Given Loeb's fundamental problems with the totally basic methodology of theoretical physics – including thought experiments and long periods of careful and patient thinking uninterrupted by experimental distractions – I think it is much more reasonable to say that Loeb clearly isn't a theoretical physicist so his subtitle is a fraudulent effort to claim some authority that he doesn't possess.

OK, Loeb tried to hijack Galileo's name for some delusions about (or against) modern physics that Galileo would almost certainly disagree with. Galileo wouldn't join these Aryan-Physics-style attacks on theoretical physics. At some level, we may consider him a founder of theoretical physics, too.

SETI vs string theory

But my title refers to a particular bizarre coincidence in Loeb's criticism of theorists' thinking that could be experimentally inaccessible for the rest of our (or some living person's?) lifetimes. He wants the experimental results right now, doesn't he? A funny thing is that Loeb is also a key official at the Breakthrough Starshot Project, Yuri Milner's $100 million kite to be sent to greet the oppressed extraterrestrial minorities who live near Alpha Centauri, the nearest star of ours except for the Sun.

String theory is too speculative for him but the discussions with the ETs are just fine, aren't they? Loeb seems aware of the ludicrous situation in which he has maneuvered himself:
At the same time, many of the same scientists that consider the study of extra dimensions as mainstream regard the search for extraterrestrial intelligence (SETI) as speculative. This mindset fails to recognize that SETI merely involves searching elsewhere for something we already know exists on Earth, and by the knowledge that a quarter of all stars host a potentially habitable Earth-size planet around them.
From his perspective, the efforts to chat with the extraterrestrial aliens are less speculative than modern theoretical physics. Wow. Why is it so? His argument is cute as well. SETI is just searching for something that is known to exist – intelligent life. However, the thing that just searches for something that is known to exist – intelligent life – would have the acronym SI only and it would be completely pointless because the answer is known. SETI also has ET in the middle, you know, which stands for "extraterrestrial". And Loeb must have overlooked these two letters altogether.

It is not known at all whether there are other planets where intelligent life exists, and if they exist, what is their density, age, longevity, appearance, and degree of similarity to the life on Earth. It's even more unknown or speculative how these hypothetical ETs, if they exist near Alpha Centauri, would react to Milner's kite. We couldn't even reliably predict how our civilization would react to a similar kite that would arrive to Earth. How could we make realistic plans about the reactions of a hypothetical extraterrestrial civilization?

On the other hand, string theory is just a technical upgrade of quantum field theory – one that looks unique even 50 years after the birth of string theory. Quantum field theory and string theory yield basically the same predictions for the doable experiments, quantum field theory is demonstrably the relevant approximation of stringy physics, and this approximation has been successfully compared to the empirical data. Everything seems to work.

The extra dimensions are just scalar fields analogous to those that are known to exist that are added on the stringy world sheet (and in this sense, the addition of the extra dimension is as mundane as the addition of an extra flavor of leptons or quarks). We have theoretical reasons to think that the total number of spacetime dimensions should be 10 or 11. Unlike the expectations about the ETs, this is not mere prejudice. There are actually calculations of the critical dimension. Joe Polchinski's "String Theory" textbook contains 7 different calculations of \(D=26\) for the bosonic string in the first volume; the realistic superstring analogously has \(D=10\). This is not like saying "there should be cow-like aliens near Alpha Centauri because the stars look alike and I like this assertion".

How can someone say that this research of extensions of successful quantum field theories is as speculative as Skyping with extraterrestrial aliens, let alone more speculative than those big plans with the ETs? At some moments, you can see that some people have simply lost it. And Loeb has lost it. It makes no sense to talk to him about these matters. He seems to hate theoretical physics so fanatically that he's willing to team up not only with the Šmoit-like crackpots but also with extraterrestrial aliens in his efforts to fight against modern theoretical physics.

Too bad, Mr Loeb, but even if extraterrestrial intelligent civilizations exist, it won't help your case because these civilizations – because of the adjective "intelligent" – know that string theory is right and you are full of šit.

And that's the memo.

P.S.: I forgot to discuss the "intellectual power" paragraph:
Given our academic reward system of grades, promotions and prizes, we sometimes forget that physics is a learning experience about nature rather than an arena for demonstrating our intellectual power. As students of experience, we should be allowed to make mistakes and correct our prejudices.
Now, this is a bizarre combination of statements. Loeb says "physics is about" learning, not demonstrating our intellectual power. "Physics is about" is a vague sequence of words, however. We should distinguish two questions: What drives people to do physics? And what decides about their success?

What primarily drives the essential people to do physics is curiosity. Physicists want to know how Nature works. String theorists want lots of more detailed questions about Nature to be answered. Their curiosity is real and they don't give a damn whether an ideologue wants to prevent them from studying some questions: the curiosity is real, they know that they want to know, and some obnoxious Loeb-style babbling can't change anything about it.

Some people are secondary researchers. They do it because it's a good source of income or prestige or whatever. They study it because others have made it possible, they created the jobs, chairs, and so on. But the primary motivation is curiosity.

But then we have the question whether one succeeds. The intellectual power isn't everything but it's obviously important. Loeb clearly wants to deny this importance – but he doesn't want to do it directly because the statement would sound idiotic, indeed. But why does he feel so uncomfortable about the need for intellectual power in theoretical physics?

He presents the intellectual power as the opposite of the validity of physical theories. This contrast is the whole point of the paragraph above. But this contrast is complete nonsense. There is no negative correlation between "intellectual power" and "validity of the theories that are found". On the contrary, the correlation is pretty much obviously positive.

At the end, his attack against the intellectual power is fully analogous to the statement that ice-hockey isn't about the demonstration of one's physical strength and skills, it's about scoring goals. When some parts are emphasized, the sentence is correct. But not too correct. The demonstration of the physical skills and strength is also "what ice-hockey is about". It's what drives some people. And the skills and strength are needed to do it well, too. The rhetorical exercise "either strength, or goals" – which is so completely analogous to Loeb's "either intellectual power, or proper learning of things about Nature" – is just a road to hell. The only possible implication of such a proposition would be to say that "people without the intellectual power should be made theoretical physicists". Does he really believe this makes any sense? Or why does he mix the validity of theories with the intellectual power in this negative way?

Well, let me tell you why. Because he is jealous about some people's superior intellectual powers compared to his. And he is making the bet – probably correctly – that the readers of Scientific American's pages are dumb enough not to notice that his rant is completely illogical, from the beginning to the end.

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