Theoretical physics and education: Does it really matter a great deal about what happens inside a black hole, or about Hawking radiation?

Question

I stumbled across this article http://blogs.scientificamerican.com/cross-check/2010/12/21/science-faction-is-theoretical-physics-becoming-softer-than-anthropology/

It got me thinking. Why do we really care to make predictions, if we can't falsify them?

I'm certainly not talking about all of theoretical physics, I'm very aware of it's usefulness, but it seems that we're wasting resources on untestable hypotheses. Does it really matter a great deal about what happens inside a black hole, or about Hawking radiation? These are, in my opinion, ideas that won't be testable for sometime, if at all. I (and other physics students in my classes) question if this is really a constructive way to spend our time.

I'm just a first year (almost second!) year physics student, so perhaps something has evaded my attention? I don't mean to seem confrontational, so please don't start a flame war.

Answer 1

Physicists are tasked to construct models of reality that are internally consistent and that have predictive power. Working on black holes and Hawking radiation fits this bill.

The growing theoretical framework on black hole thermodynamics is absolutely essential to eliminate any internal inconsistencies that seemed to affect thermodynamics when applied to extreme gravity situations. The great contribution of Hawking is that he has demonstrated that thermodynamics (which is capable of making zillions of predictions) is internally consistent, also in the presence of gravity.

John Horgan writes:

"Physicists conjecture what’s happening at the Planck scale, a microrealm even more distant, in a way, than the farthest reaches of the universe. [..] They postulate strings, membranes, higher dimensions and other stuff whose existence, like that of God, cannot be proved or disproved. Do these imaginings even deserve to be called faction?"

With all due respect, John Horgan's questioning the scientific usefulness of quantum-gravity research shows a profound lack of understanding how science works. We have to think about the Planck scale, there is no way we can ignore this physical realm even when direct experimentation in this area seem remote for the time being. An internally consistent quantum gravity theory compatible with all known physical observations would constitute an unparalleled triumph in hard science. Experimental verification is essential, but can come (much) later.

Answer 2

The idea that every prediction should be falsifiable is good as a first approximation. But the science is complex, and in it everything is linked to everything, almost literally. So actually we never know if some unfalsifiable prediction would be of any use. It can become falsifiable later. It can lead to some ideas which would lead to some new falsifiable predictions. It can improve out maths. And so on.

And don't forget the pure interest that drives scientists to make all predictions and wonder all questions they can. It is just great to know what happens in places we cannot look in. What is beyond the horizon? On the other side of the Earth? On the dark side of the Moon? In the center of the Sun? In the middle of the Big Bang? Maybe an answer is not a prediction in the strict sense, but it also is not a blind guess, it applies our knowledge to some new problem.

Answer 3

I will have a go at an answer.

Many good theoretical physicists attempt to create the Theory Of Everything (TOE): a mathematical theory that will model anything we observe in physical reality. Very many of them are concentrating their effort on some model using string theory.

Suppose that we find a TOE that fits all known elementary particle data and all known cosmological observations. This theory inevitably will be predicting non falsifiable phenomena, but also it should be predicting for example, the fact that we are living in a momentarily stable cosmos. In such a theory, as an example, it might be that if black holes did not radiate away by Hawking radiation, the universe would all have disappeared into black holes after the first 1 billion years from the Big Bang. Note, this is an example. Then even though we might never get next to a black hole to test Hawking radiation from them it would still be a strong prediction of the TOE.

Now it will take a long time for a TOE to appear and be verified, but if theoreticians were not willing to play with the mathematical models, humanity would never find the TOE, which might give us incredibly new insights into the microcosm of particles and interactions. It took about 2300 years from the first theory of an atom to get it established as a reality, and about 200 years from the modern observation of atoms to theories of the nuclear interactions.

At each new insights of theory a lot of practical gains were made for humanity, particularly when the theory of quantum mechanics was established which together with the electromagnetic theory gives us this screen where we communicate.Lets hope that with so many physicists working on a TOE the time will be diminished to some decades .

Answer 4

First of all, one has to distinguish between indirect and direct predictions theories. For example concerning theories describing physics at very high energy regimes, such as energy scales where quantum gravity effects are expected to kick in, it is clear to everybody that these high energy scales are with the current technologies not DIRECTLY accessible at the moment. Nevertheless, people working on the phenomenology of these theories are able to extract INDIRECT predictions and hints, that can be observed or excluded at the "low" energy scale that are accessible at the LHC, from cosmological observations, direct searches etc ... So claiming that physics is not falsifiable just because the regime it is intended to work is not directly accessible is simply wrong.

Second, with the advanced theories we have today in fundamental physics, the aim is no longer to confirm them by a single observation as it was possible in the past, but rather (more or less direct) hints are accumulated that speak in their favor and increase the trust we have in them. However, for many theories it is still possible to falsify them by a single observation of theoretical consistency considerations.

Just recently, there has appeared an interesting work of science philosophers who succeeded in proving by probability theory that the so called "No alternative argument" can legitimately increase the trust in a theory describing the physics of a regime that is not directly experimentally accessible, just because nobody is able to come up with a viable alternative.

So it is certainly not justified to say that doing physics valid at regimes that are not directly accessible at present is a waste of resources and money etc. Young people interested in fundamental physics questions should not be discouraged by such negative statements in popular media and magazines ( by people who are often not experts in these fields) from following these interests and taking a corresponding path in their career. As too often since quite some time ago, the Scientific American is reporting about fundamental physics in a way to pessimistic and negative way which is orthogonal to what physicists actually working in these fields think. To get reliable information about such topics and questions, one better does not rely on the Scientific American these days. A better source of honest and well explained information about particle physics and other fundamental physics topics is Prof. Matt Strassler's site for example.

Answer 5

Your question is essentially asking for opinions and will therefore likely be closed, but I think what you're missing is the fact that in any discipline where theoretical questions are inextricably linked with experimental questions it's impossible to judge in advance which theoretical questions are going to have practical ramifications. Physics and science do a pretty good job of not expending resources on ideas once they have been proven not to work, which is all one can really ask. Disincentivizing a Hawking or a Penrose based on someone's amateur opinion of the potential value of their work would be just about the dumbest thing you could possibly do.