Progress in the foundations of physics has been slow since the 1970s. The Standard Model of particle physics is both very successful, but also displays a fundamental weakness: it can’t make sense of gravity. Physicists have pursued a number of pet projects, like supersymmetry and string theory, claiming they held the key to overcoming the Standard Model’s shortcomings, but at this point they seem like failed projects. So how can theoretical physics become unstuck? According to Sabine Hossenfelder, any improvement on the Standard Model goes through understanding the main conundrum of quantum mechanics: the measurement problem.
Physicists have been promising us for more than a century that a theory of everything is just around the corner, and still that goal isn’t in sight. Why haven’t we seen much progress with this?
Physicists made good progress in the foundations until the 1970s when the Standard Model of particle physics was formulated in what would pretty much be its current form. Some of the particles were only experimentally confirmed later, the final one being the Higgs-boson discovery in 2012, and neutrinos became masses, too, but the mathematics for all that was in place in the 1970s. After that, not much happened. Physicists pursued some dead ends, like grand unification, supersymmetry, and string theory, but nothing has come out of it.
The major reason that nothing has come out of it, I think, is that physicists haven’t learned from their failures. Their method of inventing new theories and then building experiments to test them has resulted in countless falsifications (or “interesting bounds”, as they put it in the published literature) but they keep doing the same thing over and over again instead of trying something new.
But not only do we have plenty of evidence that tells us the current method does as a matter of fact not work, we also have no reason to think it should work: Guessing some new piece of math has basically zero chance of giving you a correct theory of nature. As I explained at length in my 2018 book “Lost in Math”, historically we have made progress in theory development in physics by resolving inconsistencies, not by just guessing equations that look pretty. Physicists should take clue from history.
It’s no secret that the Standard Model is in some serious trouble. What do you see as its weakest point?
I wouldn’t say the Standard Model is in serious trouble. It’s doing an amazing job explaining all the data we have. In fact, for particle physicists the biggest trouble with the Standard Model is that it’s working too well.
Its weakest point is that it doesn’t include gravity. We’ve known of this problem since the 1930s, but we still haven’t resolved it. A secondary issue is the origin of neutrino masses. Those two problems though will not require a solution until we hit energies at least a billion times above that of the Large Hadron Collider. This is why I don’t think building a bigger collider is the right thing to do at this moment in time: It wouldn’t get us anywhere near to testing the interesting parameter range anyway, it would just waste a lot of time, money, and effort.
I guess your question was alluding to some data anomalies that don’t seem to fit into the Standard Model. Anomalies always exist, they come and they go. I don’t think any of the current anomalies are particularly convincing evidence that something needs to be changed about the Standard Model.
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