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Comment by aroberge | Hacker News Reader

Dr. Sabine Hossenfelder is an opiniated physicist who gets a lot of flak for constantly commenting on this issue. Yet, I believe she does society a service in doing so.

I have yet to see anyone contradict her basic premise with factual information. I wish she were wrong, as I would love to see a breakthrough towards an experimentally verified Grand Unified Theory, including an explanation for what we currently identify as dark matter (similarly for dark energy). From what I read, physicists that criticize her take their own wishes for reality, and prefer to attack the messenger rather than confront the reality of the message.

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It's hard to be loved when one wants to take money away from other people and their projects. A more promising line of action would be building another community of particle physicists with different goals than building a bigger collider, possibly aligned with Hossenfelder's suggestions. In this way they'll have something to gain and will fight for the budget that otherwise would go into the collider.

I'm not sure we're improving anything when we discover some public good is flawed, mediocre, or maybe even a little corrupt and respond by tearing it down and replacing it with nothing.

I think we've done enough of that. At this point I'm really only interested in positive proposals, what new stuff can we do? If we have a wave of new successes any old failures will fade out on their own.

Hossenfelder proposes the stuff at point 18 of http://backreaction.blogspot.com/2019/03/nonsense-arguments-...

I have no idea of they are something particle scientists do or if they belong to another branch of physics.

Sure the base is covered, but I'm calling for "20 arguments for quantum gravity experiments" and #18 is "we've tried bigger and bigger particle colliders and the results are disappointing"

Everything's disappointing, I am (ironically given my tone here) only interested in hearing from those leading with solutions.

Then read http://nautil.us/issue/45/power/what-quantum-gravity-needs-i... linked to from point 18.

In summary, the reason for quantum gravity experiments is that investigating contradictions in our theory has always been the best source of progress in science, and experiment has to lead theory. We know that QM and GR contradict each other, and therefore we should research that.

She gives a variety of experiments that can research that. The equipment for which is of use in a variety of other sciences. (Particularly astronomy.)

I am not conviced. I mean, you wouldnt want/know what to do with 5 Billion (just looked up the LHC value, I am not sure what the amount of the new proposed accelerators would be) for these kinds of experiments, probably 100 Million would be plenty. If you think that Iter is 15 Billion then 5 Billion doesnt sound so much. (Also in the grand Scheme of things like 50 Billion is not much)

You mean like RHIC and JLAB? They had to compete mightily over comparative trump change for an upgrade to an electron-ion collider? (RHIC won but JLAB will contribute)

There are plenty of other areas of real research that are still nominally 'particle' physics that are actually able to put to paper real goals for what they expect to achieve.

There are also facilities like NSLS II that are heavily subscribed and doing research that is both very real world and pie in the sky.

Keep this in mind too - the Tevatron at FNAL would have had the Higgs discovery if they could have run another 3-5 years - they already had data order 3 sigma IIRC. Likewise, they would have had a lot more data on the top, something LHC has been gathering since the confirmation of the Higgs. This would have come at a fraction of the cost of the Higgs. Beyond that, has Higgs done anything more than add to the already known to be narrow avenues left for SUSY?

She is absolutely correct that the particle physics community needs their feet held to the fire to justify such an enormous single outlay and being a jobs program for a few thousand physicists is not one of them.

This

Collider projects were much more interesting to a public who had remembered the sea change of reactors and the bomb. While I love the LHC, from a productivity standpoint there are other projects which have been bearing more fruit for ~50 billion.

Her opinion is totally legitimate and I’m glad people like her are speaking up. Everyone should agree that we need to spend money pushing the limits of science. That’s not the issue here. The point of Sabine’s criticism is that these empty promises need more scrutiny based on the failures of the recent past.

I don't really understand that argument. What does a failed prediction about super-symmetry in 1996 have to do with the opportunities of the next collider? How does "we didn't find evidence for or against supersymmetry at LHC" connect to dark matter experiments in its successor?

I'm also not really convinced of what she categorizes as failure. She enumerates quite a few incorrect predictions, but is that sufficient to show that the experiments were a failure? There are literally thousands of papers published because of the LHC and CERN claims hundreds of results. Maybe you can show that they are mostly worthless (which is not the same as boring or not spectecular), but she doesn't really seem to even try to do that.

> She enumerates quite a few incorrect predictions

You make a good point - without the expensive accelerator data, we’d have no idea that these omg ridiculous stupid waaaa predictions are true or false!!!

> You make a good point - without the expensive accelerator data, we’d have no idea that these omg ridiculous stupid waaaa predictions are true or false!!!

No, even with the accelerator data we probably still won't be able to conclusively rule out many approaches. We'll only be able to rule out overly specific variants of those predictions. Which, given the infinitude of available theories, doesn't do much to narrow things down.

Think of it this way: At one point, geocentric theories of planetary motion based on nested crystal spheres were requiring ever more elaborate arrangements with more spheres. More observations with greater precision only required adding more spheres.

We're somewhat in the same situation WRT high-energy physics today, in that larger and more powerful accelerators will only rule out particular theory variants, just as more powerful telescopes would only have ruled out particular arrangements of crystal spheres. Just as geocentrism as a category of theories isn't falsifiable by greater precision, many of the current approaches toward HEP aren't falsifiable by ever more powerful accelerators. You can always add another dimension or mathematical elaboration to explain the observations.

Which simply means that right now, another large particle accelerator probably isn't the most useful experimental approach to figuring out how to reconcile the two well-supported theories we do have.

That's the Hossenfelder take on the scientific method for you: whereby you make the experiments to confirm the theory. Which is fantastic because if science had ever worked that way you would be done with all experiments as the sensible ones would give known results, so what's the point.

The point is that you can spend a lump of money to check things out in that way, and fine - especially when you have the Higgs to confirm as well. But if you want to double down you need to have better evidence and a better argument. This is the logic that applies in any lab; sure take a punt look at x or y, if you're right then you'll get a grant and your career will thrive. If you're wrong you're out.

That's happened to many people (Hossenfelder included?) but it's now happening to the community and no one likes it. But given that is how science as an institution operates they shouldn't be surprised.

Here's a thought experiment. Would there be a bid for a new 100Tev machine if super symmetry had been confirmed at LHC? My bet is :for sure. And the key argument would be "we told you that we were good last time, so you have to back us this time"

The thing is we didn't know whether the mechanism of electroweak symmetry breaking involved the Higgs or something else. But we knew that there would be particles associated to electroweak symmetry breaking at TeV scale because of a unitarity bound, among other reasons (as happens with this particular kind of dark matter at 100 TeV that Sabine dishonestly calls "weasel words").

Something had to happen at that scale, the Higgs wasn't guaranteed. Sabine gets experimental physics backwards because no one planned the LHC to confirm the Higgs, but to know whether the Higgs existed and if it didn't what did instead. My money was mostly on it not showing up; many physicists were convinced it wouldn't, then it was there but we couldn't know beforehand.

There's a scientific case for making precision measurements of it, as was done with the electroweak bosons for very good reasons that she dismisses without showing any kind of understanding about the research she wants to shut off.

Were there other theories that explained why the elementary particles have mass except for the Higgs?

Regardless, the point stands: we knew that something is missing from the Standard model, and we knew that it must exist in a very precise range of energy. If it didn't exist there, it could have called into question the whole SM.

In contrast, we don't know that there must be some kind of dark matter at the 100TeV scale. We know that one particular type that we have thought about could exist, but we have other candidates as well, and there are ways that the 100TeV prediction could also be moved to higher energy levels.

Meanwhile, we don't even know if dark matter is a kind of matter or a modification of the force of gravity or a problem with approximations of Einstein's equations used in practice etc.

Sure, for instance EWSB by strong dynamics such as Technicolor. Here's a well known review from back in the day: https://arxiv.org/abs/hep-ph/0203079

I'm not sure we're done with composite models. There are more exotic alternatives and then the fact remains that neutrino masses aren't in the SM.

I consider pretty hopeless to keep thinking that you can modify GR like plasticine in all the instances in which putting amounts of matter that doesn't radiate works (maybe it works because it's there and its effects on other stuff is how you "see" it). It has the appeal of making some people feel like they can call a whole profession or several a bunch of crooks, and that's pretty much what it has going for it outside of the scientists working in earnest on it.

> you make the experiments to confirm the theory

The scientific method has usually worked by either coming up with theories and testing them; or by measuring things we thought we knew and finding new explanations when those turn out to be false.

What has not really worked too often has been coming up with mathematical models out of thin air, fitting them to all of the current data, extrapolating them to things we haven't been able to observe yet, and then building those things to check if they also worked.

That is why research into astronomical objects to ever greater precision is a promising candidate: we know what we expect to find if our current theories are correct, we know of real problems with our theories, and we can come up with new theories that predict such and such structures that should be visible in precisely such and such conditions.

This is the exact same model of how physics advanced from Tycho Brahe to Newton - people had models of the motions of the stars, they collected data to confirm those models, and found problems that they couldn't explain. Then Newton came along and found a mathematical model that, for the first time, explained those observations, and even reconciled them with other observations on the ground. We then spent a lot of time testing Newton's theories and didn't find any holes for a few hundred years.

Along came electromagnetism, the study of its dynamics, and the discovery of the speed of light problem, which couldn't be explained - requiring a new model that could actually explain everything we knew + the new data, and so on.

> What has not really worked too often has been coming up with mathematical models out of thin air, fitting them to all of the current data, extrapolating them to things we haven't been able to observe yet, and then building those things to check if they also worked.

But this is the story of early to mid 20th century physics! General relativity, the initial quantum mechanical theories, Dirac’s equation and anti-particles, neutrinos were all the product of this process of adding mathematical conveniences and extrapolating to things that turned out to be real. You can argue that more recent efforts in this direction have been much less successful than those were, but I think you have to turn a completely blind eye to the history of modern physics to claim that method “has not really worked too often”.

I don't think general relativity at least fits into this model: general relativity explained phenomena that special relativity just couldn't, and that were already well known to exist (gravity, objects of equal mass falling at equal speeds, time dilation in relation to acceleration).

I'm less well versed about the other subjects you mention, but there were several unsolved problems in physics at that time that absolutely required new theories (the photoelectric effect VS the wave behavior of light, black body radiation, the need to reconcile quantum mechanics with special relativity). In all of these cases, we had unexplained data or inconsistencies between theories.

By contrast, most of the theories that could be tested with a new collider are not solving anything - they are just theories about things that might exist, but could very well not exist at all. There is no hope of gaining insights into the measurement problem or quantum gravity at the next collider.

Even the theories of dark matter that could be tested are still too early to be worth a 20b bet. There are too many equally plausible theories of dark matter to say any one of them is promising enough to be worth that amount of money. And even ruling one of them out will not have a major effect on the field. It's not like it would rule out string theory, for example.

> What does a failed prediction about super-symmetry in 1996 have to do with the opportunities of the next collider?

There are two criticisms she articulates very clearly:

1. SUSY is not a testable theory, as it can always "retreat" to higher energy levels, without any real limit.

2. There is no scientific reason to believe SUSY should be true - it doesn't solve any real problem with any of the known theories of the universe. There are infinitely many ways that the universe could be different wherever we haven't looked yet - we can't possibly test all of those theories.

The combination of both arguments leads to the following "law": until we have a theory that solves unsolved problems in physics AND that makes concrete predictions with bounded parameters (so that a failure will explicitly rule out this theory, instead of pushing it endlessly to "maybe at higher energy levels"), we shouldn't be paying huge amounts of money to test things blindly.

This is the fundamental difference between, say, the Higgs prediction and SUSY - we were looking for a concrete thing that it was necessary to exist for the rest of the Standard Model to make sense; and we knew a clear range of energies where the Higgs must exist; if we found it like we did, we know the theory was correct. If LHC didn't find the Higgs, then it would have definitively ruled it out, leading to an explicit need for a new SM.

By contrast, SUSY has not been confirmed, but it is also impossible to rule out entirely, and none of our models NEED SUSY to be right - so in the end, experiments for SUSY don't achieve anything. We might as well be launching space missions to look for Russel's teapot.

In my opinion the problem with her messaging is that while she says that we should not fund the next collider, I think the argument should be, what's the best allocation of money in physics? And there are legitimate reasons to have the next collider even if we have no guarantee that it will deliver GUT or whatever. We have to venture into the unknown. We just should not lie that it will prove supersymmetry or is guaranteed to find dark matter because it sounds better.

Let's not pretend that we can't find some other way to allocate billions of collider dollars. I don't see it as a problem with her argument that she doesn't promote an alternative, because I'm sure then the critics would say that the alternative isn't promising enough. Yes we need to go into the unknown, but the point is that at some point, it's not cost effective to do that, and we live in a world with constrained resources where we can do more good by investing elsewhere.

How can you seriously make an argument about efficient allocation without discussing the alternatives you choose between? Is it even logically possible to define efficiency without comparing alternatives?

Have you defined the word "seriously" before making that comment? Ridiculous.

Yeah, it does get tiring that all the novelty in her writing shows up in the sections describing the well known history of the standard model resisting all attempts at being made into a theory.

But apparently the only point worth making is progress in particle physics has been slow. Well, to be fair the point Hossenfelder tries to make is that there's been no progress, and since that's not actually true convincing people of it regardless takes more work.

She has specific proposals - climate science (the most pressing concern of our times, if organized human society is to survive the next century or so), and astronomical research.

I would also mention that things like the Voyager missions are still providing novel data ~50 years after their launch. Will the same be true of the LHC, or any other particle collider?

I have bad news for you: Most high energy physicists I know go on to finance or "data science" before they would work on climate science. It is just not that interesting and doesn't pay well. HEP carriers prestige and is actually something aspiring physicists want to do.

That's not really bad news, is it? It doesn't seem unreasonable to redirect all the money being spent on HEP projects into climate science. That high energy physicists have great employment options is a good thing. It makes it much easier to close down those projects.

The HEP problems aren't going anywhere. Lets deal with more pressing concerns now and come back to HEP problems later.

It is really hard to organise 6000+ people to do anything. HEP won’t come back if you do. There isn’t much to figure out on climate change on a fundamental level anyways. It is a political and technological problem, not something you need a ton of scientists working on.

Organizations and cultures are kind of like living beings in this regard. The relationships and unspoken understandings between those 6000+ people are not things that could be replaced easily.

This is e.g. why the current rocket companies had to do a lot of reinvention and research instead of just switching the Saturn V production line back on.

> It is really hard to organise 6000+ people to do anything.

For sure, but we know we can do it because we've already done it.

No, you cannot reestablish HEP. HEP was extremely attractive to the theoretical inclined physicist because it contained a lot of unexplained data. There is no unexplained data now, HEP currenty lives on on the momentum it has. If you reduce this momentum to zero it will be gone (it will also be gone in 20 years if nothing is found)

It's kinda like the nuclear power industry. There was a huge investment by the government with an interest to build weapons. Some of it spilled over to energy plants. Once the government got what it wanted and had enough bombs funding was pulled. Nuclear power plants did ok for a while. Then decades passed and just a skeleton crew remains. Restarting the momentum is only possible through massive cost overruns.

Sure, but if the money were redirected to climate science, then the climate science people would be the well-payed ones, wouldn't they?

Also, there are other avenues for particle physics that don't require 20 billion dollars to start with. The 20 billion isn't going to retaining particle physicists, it's mostly going to hardware, engineering construction etc. efforts.

To be fair it’s not like HEP pays well. And redirecting the resources that currently flow to HEP to climate science wouldn’t make much difference, as it’s not a particularly large amount of resources in the grand scheme of things. HEP has a lot of people who work there for a lot less than they could make elsewhere because they like being physicists. If the field is gutted in favor of some other discipline they will move to finance or industry, not other scientific fields. We can approximate where they would end up be looking at where PhD graduates who don’t go into physics research end up.

Yes, climate is a pressing concern, but you are aware that climate science is descriptive an not a solution at all (more climate science will not change carbon emission). More funding on ITER might though (but I wouldnt call that climate science).

and I don't think she's even saying we shouldn't ever fund the next collider. I think she's suggesting that maybe we should wait until at least:

- many interesting falsifiable theories emerge that are resolvable at the accessible energy scale.

- technology catches up to make the engineering of such a thing cheaper.

It's not a terrible idea to wait. An important part of why the LHC was more effective than the hole in texas is that chemists using NMRs and doctors using MRIs drove technical and production improvements that brought down the cost of superconducting magnets.

There is this narrative that theoretical physics drives investments in technical innovation that improves other scientists, but I'm not sure that narrative is entirely true. It's often the other way.

She had a talk[1] at the Perimeter Institute a few years ago, which I recall thinking was rather good.

[1]: http://pirsa.org/17110133

yeah more funding and focus should start to focus on stuff like this: https://en.wikipedia.org/wiki/An_Exceptionally_Simple_Theory...

Time to spend some money else well.

> yeah more funding and focus should start to focus on stuff like this: https://en.wikipedia.org/wiki/An_Exceptionally_Simple_Theory...

This Wikipedia entry is 1) generically about the type of unproven theoretical model without experimental support that is used in an attempt to justify investment in the next big collider; 2) more specifically, about a theoretical model that has been shown to be wrong in terms of describing what we observe.

Lisi's work is generally considered extremely unlikely by physicists. The eye-catching title and colorfulness of its author attracts a lot of attention with the public, but it doesn't match experiment. It has basically been abandoned.

I agree that we could probably spend billions of dollars better than on another enormous collider, even within high-energy physics, but it probably wouldn't be best spent on E8 Theory. Figuring out how it would be best spent, however, would be contentious to say the least.

be interested to see those paper that disproves them. Can't be any worse then the string theory.

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