I think a little context here is in order: from a 10000-foot high level, the particles that can be seen depend on the amount of energy present in the system, which is why we spend billions of dollars accelerating basic particles (protons in the case of the LHC) to high energies and literally SMASH them together, so we can see what flies out.
We see four distinct, different forces in the universe: strong and weak nuclear forces, electromagnetism, and gravity. Our Standard Model predicts that these forces become more unified at higher energy levels:
1. Electromagnetism merges with weak nuclear force at 246 GeV
2. Electroweak force merges with strong nuclear force at around ~10^16 GeV ('grand unification')
3. Finally, quantum mechanics predicts these forces become unified, which is to say indistinguishable, at the Planck energy, around 10^19 GeV.
As we get closer to predicted unification energies, we see different mixes of particles, and the Higgs boson is in fact the particle responsible for electroweak symmetry breaking, with a mass of around 126 GeV.
The problem is that the LHC produces collisions of around 10^4 GeV, so from our current energy scale up to the next unification, with the strong force, we're off by a factor of 10^12.
Back of the envelope estimate is that a supercollider that can reach grand unification energies with our current technology would be around the size of the solar system.
Hence the article: particle smashing is a brute-force approach to investigating new physics, but now there is an extremely wide gulf between what we have discovered, and what we think lies next, hence we need to be more clever than using brute force.
This explanation needs a couple of major caveats: The Standard Model does predict unification at ~250 GeV, but it does NOT predict unification at either 10^16 GeV or 10^19 GeV. Those predictions come from particular extensions of the Standard Model (grand unified theories or various quantum gravity models, respectively) which have been studied by particle theorists for their simplicity.
Which is to say: Those unification scales come from speculative models, not from tested physical law. We do not know with any certainty what lies beyond the energy scales we've tested. You should take with a generous grain of salt any claims that we have physical models that work across an additional 14 orders of magnitude. Consider the range of phenomena that we've discovered in moving from the ~1 cm scale of a glass of water to the 10^-14 cm scale where quantum chromodynamics kicks in.
I usually just use the upvote button, but in this case, I must join some other commentors in expressing explicit gratitude for your easy-to-understand explanation.
Minor clarification. The standard model does not describe gravity. It ignores it, which is fine at LHC energies because it's orders of magnitude weaker than the other three forces.
At the planck energy scale, this is no longer the case, the relativistic mass of particles becomes so big that gravitational interaction is too strong to be ignored, and the SM loses it's ability to predict how particles interact, decay, combine etc
The solar system is already close to a vacuum. Makes me wonder if a new solar system sized accelerator could just be a series of nodes orbiting far out to aim and accelerate the particles around.
Still way too hard for us but also way easier than building a tube going around the solar system.
You put everything in a way that someone with high school physics can mostly understand the issue. Would it be possible for you (or anyone else) to explain what is merging of forces? Or is it beyond high school?
How does this map to the idea that we haven’t unified the fundamental forces? It sounds as if we understand exactly where and how they diverge... surely it isn’t just that we haven’t experimentally verifies this?
Is there some reason why new phenomena can't occur except at these energies? Couldn't there be something interesting that isn't the unification of forces?
I find it fascinating that the prevalent comment on this are variations of "that can't be right, we still don't understand [things, such as dark energy, etc]." It demonstrates one of the most pernicious biases in science.
Particle accelerators have been the mainstay and principle tool for particle physics, and have produced amazing results. Further, there are obvious questions in fundamental physics that the Standard Model revealed by these experiments does not answer. But, it does not follow these further questions can be answered via accelerators that us humans can construct. The universe has made no promise to us that its mysteries are accessible, least of all through some particular method. We had a particular reason to believe the LHC would reveal new physics (the Higgs boson prediction) and we have no such reason for the proposed future accelerator; our evaluation should change as a result.
My guess would be that astrophysics is a better route to understanding the mysteries of fundamental physics; astronomers can measure distant phenomena with surprising accuracy already, and objects such as black holes are one of the few cases where exotic phenomena are currently widely expected to occur. Perhaps the money is better spent on a truly gigantic space telescope?
the James Webb space telescope was originally supposed to only cost 1 billion, but now is around 10 billion USD. Still, we could build two more of those for the price of a new LHC.
And the JWST is going to give us insights about galaxy formation, exoplanets, and more!
I'm pretty sure someone said everything in physics has been discovered just before the start of the 20th Century boom in theoretical physics too.
Michelson (of Michelson-Morley fame), apparently, IIRC. I'd warrant that despite his credentials Yang (of Yang-Mills fame) is making a similar mistake.
But I do think we're likely to see a retarding of the pace of change in fundamental physics (I think we're on to a reflective phase, where science consolidates, and social change progresses; leading to more focus on higher-order sciences - biology and such).
Several years ago, shortly after the Higgs discovery, I sat down with a couple CERN people, and their comment was that the current problem is that we need more theoretical physicists coming up with measurable predictions. As many of the other posters state, obviously there is more to learn, but we could learn faster if we had better (and more) predictions about what we might find.
It's harder and harder to do without well developed intuition. To develop good intuition, we need to make good mental model, but we got good (but incomplete) mathematical model instead.
As a layman, from your statement, what do we have now? [meaning if we don't have enough theoretical physicists]. Is it that we have enough theoretical scientist, but the predictions are not testable? Or not enough talent?
I could not disagree more with the general statement of the author.
Actually, we are now going from a boring phase of particle physics where the theory was able to predict anything we were able to measure afterwards to a phase where no theorists has a clue what might happen.
This phase is called "exploration". It consists of many "blue shots" of which many will probably have zero results but have to be done in order to find out what is really going on. Theorists had a good run with prediction, now it's the experimentalists turn to lead the way with exploration by producing new data.
When the Muon (basically a heavy version of the electron) was first discovered it 'seemed so incongruous and surprising at the time, that Nobel laureate I. I. Rabi famously quipped, "Who ordered that?"'[Wikipedia]
The new CERN collider has got to be build. To risk to miss the next great "Who ordered that?" moment would be grossly inconsequential.
I feel this comment assumes that experimentalists weren't "exploring" this whole time.
There are many, many, MANY papers that fly out of these particle physics experiments. Most of the papers are about how they do not find stuff.
These papers take the form: "Search for the pair production of X in proton-proton collisions at s√ = 13 TeV" or other more generic papers where they just look for anomalies against Standard Model predictions. Fun fact - nothing found yet! This was the case at the Tevatron, where countless experimentalists poured over the data trying to find the slightest hint of something new. It also is the case today (so far) with the LHC.
To suggest that we're in a new phase where we're going from a "boring" phase to a new one where theory doesn't know kinda misses the point that experimentalists have already been doing this.
Usually, when we reach the limits of theoretical physics we have unexplained experimental results or when the experimental side starts getting boring, we have theories that can be used to make new predictions. Right now, the problem is that there is no clear direction in which to proceed. No new theory predicts anything that can be feasibly tested and there's nothing experimentally surprising that can't be explained theoretically. Until there's a breakthrough, a theoretical framework with testable experimental predictions, there is no point in wasting a few more billion to build bigger holes on the ground in Switzerland.
While I am a theoretical physicist by training, I have no doubt that those same billions could be much better used by many other fields such as biology, chemistry, computer science, ai, etc...
I do think it's worthwhile to question building an incredibly expensive particle collider without a specific purpose in mind, when the money could go towards fields like fusion energy, quantum computing, or cancer research
We have more than enough money to do all of the above. Science is a sideshow; it absorbs a nearly infinitesimal part of the economy, and could be easily funded by a military funding decrease small enough that it'd scarcely be noticed.
Yes, a larger collider is unlikely to find much, but it's cheap enough that we should do it anyway. As bets go, it's a good one.
Put it all toward life extension and physicists can spend hundreds of years deeply researching these problems instead of having to start from scratch every generation only to get only 20-40 years of useful working life per individual.
Can someone please help me understand why anyone outside of a small circle of curious science buffs should care about particle physics?
It seems the field has advanced so far that EVEN IF new discoveries emerge, they would be of no practical value.
I'm not saying it's not interesting (I like reading about it FWIW), and I'm not saying it will never ever prove useful. But from resource allocation perspective, tens of billions of dollars required for high energy experiments seem to be much better spent on other areas of physics. That is, until the civilization advances far enough that understanding the depths of particle physics or cosmology becomes relevant.
> It seems the field has advanced so far that EVEN IF new discoveries emerge, they would be of no practical value
Particle physicists would disagree. A complete understanding of quantum mechanics, squared with general relativity, is very likely to have practical applications.
Cliche analogy: if you thought the world was flat and ships were falling off the end of the ocean, you might be investing your money in world-edge-detection; and you might say there's no point in studying the edge of the world itself because no practical value can come of it. You wouldn't have any idea that circumnavigation was (relatively) easy once you understood more about the nature of the world.
Well, it's searching for the unknown and competitively FOMO -- fear of missing out. Searching for the unknown has worked great in the past. The physicists are under enormous pressure to publish good papers, and to this end they will push hard against the unknown, by whatever cleverness, directions, ideas, means, techniques, etc. they have. They may move to applied physics, research in engineering, etc.
Maybe the real way of progressing is not by building bigger accelerators with the same technology (and of course a LHC successor would need several new evolutionary developments), but finding out ways of producing higher energy collisions without resorting to accelerating particles in a tube.
We're not even sure if there's anything in those higher energy ranges, there are certainly knowledge gaps, but maybe a bigger collider is not the answer. At least not until we have some other hints and new theoretical ideas.
I still think we have a lot to learn from Bose-Einstein condensates.
If we're hitting a wall with respect to increasing energy in a system as much as possible, maybe we should make sure we've picked all of the low-hanging fruit from decreasing energy in a system as much as possible.
It seems very strange to say that "particle physics may be done", given that are several enormous mysteries and problems in physics that clearly indicate our knowledge is incomplete.
A few examples: QFT and GR are not integrated, dark matter, dark energy, the vacuum catastrophe, and so on...
One could make the argument that a larger collider is not the best way to attack these (I have no idea), but that is a different statement.
The author's argument is not that there are not questions that still need to be answered; but there is no reason at all to believe that a larger collider, that we are capable of building with today's technology, will answer any of them. (This point is made explicit in the comments).
If the funding for your field is predicated on building a larger collider to discover new particles; then you're in trouble. That is the sense 'Particle Physics may be done' is meant in this context.
Well there is good news: The Universe contains structures capable of accelerating particles to the energies we want to observe and blasts them in our direction occasionally. It may take a lot longer, but we can observe those.
Collider physics is not the whole of particle physics. There are in fact known inconsistencies in the standard model (for example, experimental evidence shows neutrinos have mass[0]) that remain unexplained and need further study.
It takes a truly reactionary definition of "standard model" to claim that it's inconsistent with neutrino masses. The extension is straightforward and was not part of the original formulation simply because there was no experimental data requiring it when Weinberg first wrote down his model of leptons.
He also didn't include quarks, so by the same logic, the "standard model" is inconsistent with those too.
There's also the whole issue of figuring out what dark matter is made out of. Neutrinos account for a small part of it, but the rest is completely unknown.
That simply isn't true. Not discovering a new particle outside of the standard model, not discovering supersymmetry, or bumping against an energy desert does NOT spell the end of the line for particle physics any more than GR isn't over just because they discovered gravity waves. What you guys don't understand is that model building is not a hard activity at all. SU(5), SO(10), E6 whatever. Graduate students do those calculations all the time. What is hard is understanding concepts and there are more than a few surprises hidden away inside the standard model. Strange matter is poorly understood. There may be ways to pretty up the standard model that haven't been discovered yet. People like to go around complaining how "ugly" it is. It's not. It's prettier and smarter than they are, they're just jealous. Particle physics is doing just great and the only thing wrong with it is that it is dramatically underfunded.
Before we throw huge money, we have to make sure we are really using it the best way. These ever larger colliders are big investments. The Higgs was an obvious hole missing in the puzzle, let's find another obvious hole in the puzzle.
Saying particle physics is dead because we discovered all basic particles that we could with our resources - is a lot like saying biology is dead because we discovered DNA.
Stephen Hawking said something to the effect that since the Higgs was discovered particle physics was less interesting. To him but not to me. Particle physics is better off than ever. Experimentally, things are going to change immensely. Deep learning revolutionize particle physics and it's only going to get better. Technology gets better. Regarding theory, I personally think particle physics is in that same awkward stage as calculus before Weierstrass, Dedekind and Cauchy made their pioneering discoveries in analysis. Even after that there was still much to do. That was just the beginning Lebesgue, Danielle integral, Moore-Smith convergence. We're at the very beginning stages of particle physics theory. Nobody even knows what the Feynman integral really IS. Most of the mathematics we currently use is sophisticated but in another sense, quite dippy. Even superstring theory is suffused with what we'll likely look back on as broken maths. All the easier discoveries have been made and now the game is going to be different. That's a great place to be.
Perhaps quantum computers will help break the deadlock? They'll make it possible to extrapolate the consequences of theories that were previously intractable. This might mean that a large number of candidate theories could be tested wholesale to see of they match existing evidence. In particular I know that it's currently very hard to get predictions from quantum chromodynamics, which means that the standard model hasn't yet been fully tested.
[+] [-] smallnamespace|7 years ago|reply
We see four distinct, different forces in the universe: strong and weak nuclear forces, electromagnetism, and gravity. Our Standard Model predicts that these forces become more unified at higher energy levels:
1. Electromagnetism merges with weak nuclear force at 246 GeV
2. Electroweak force merges with strong nuclear force at around ~10^16 GeV ('grand unification')
3. Finally, quantum mechanics predicts these forces become unified, which is to say indistinguishable, at the Planck energy, around 10^19 GeV.
As we get closer to predicted unification energies, we see different mixes of particles, and the Higgs boson is in fact the particle responsible for electroweak symmetry breaking, with a mass of around 126 GeV.
The problem is that the LHC produces collisions of around 10^4 GeV, so from our current energy scale up to the next unification, with the strong force, we're off by a factor of 10^12.
Back of the envelope estimate is that a supercollider that can reach grand unification energies with our current technology would be around the size of the solar system.
Hence the article: particle smashing is a brute-force approach to investigating new physics, but now there is an extremely wide gulf between what we have discovered, and what we think lies next, hence we need to be more clever than using brute force.
[+] [-] auntienomen|7 years ago|reply
Which is to say: Those unification scales come from speculative models, not from tested physical law. We do not know with any certainty what lies beyond the energy scales we've tested. You should take with a generous grain of salt any claims that we have physical models that work across an additional 14 orders of magnitude. Consider the range of phenomena that we've discovered in moving from the ~1 cm scale of a glass of water to the 10^-14 cm scale where quantum chromodynamics kicks in.
[+] [-] stronglikedan|7 years ago|reply
[+] [-] walrus1066|7 years ago|reply
At the planck energy scale, this is no longer the case, the relativistic mass of particles becomes so big that gravitational interaction is too strong to be ignored, and the SM loses it's ability to predict how particles interact, decay, combine etc
So you're guaranteed to then see 'new physics'.
[+] [-] mrfusion|7 years ago|reply
Still way too hard for us but also way easier than building a tube going around the solar system.
[+] [-] fxfan|7 years ago|reply
[+] [-] high_derivative|7 years ago|reply
Do experimental (!) particle physicists have any other way of doing research on this than colliders?
[+] [-] b_tterc_p|7 years ago|reply
Apologies if I am way off base
[+] [-] unknown|7 years ago|reply
[deleted]
[+] [-] dkersten|7 years ago|reply
[+] [-] salty_biscuits|7 years ago|reply
https://en.wikipedia.org/wiki/Ultra-high-energy_cosmic_ray
[+] [-] OscarCunningham|7 years ago|reply
[+] [-] mrfusion|7 years ago|reply
Kind of like how we create magnetic force with electric.
[+] [-] maxander|7 years ago|reply
Particle accelerators have been the mainstay and principle tool for particle physics, and have produced amazing results. Further, there are obvious questions in fundamental physics that the Standard Model revealed by these experiments does not answer. But, it does not follow these further questions can be answered via accelerators that us humans can construct. The universe has made no promise to us that its mysteries are accessible, least of all through some particular method. We had a particular reason to believe the LHC would reveal new physics (the Higgs boson prediction) and we have no such reason for the proposed future accelerator; our evaluation should change as a result.
My guess would be that astrophysics is a better route to understanding the mysteries of fundamental physics; astronomers can measure distant phenomena with surprising accuracy already, and objects such as black holes are one of the few cases where exotic phenomena are currently widely expected to occur. Perhaps the money is better spent on a truly gigantic space telescope?
[+] [-] eutropia|7 years ago|reply
And the JWST is going to give us insights about galaxy formation, exoplanets, and more!
[+] [-] pbhjpbhj|7 years ago|reply
[+] [-] dboreham|7 years ago|reply
"In the next ten years, the most important discovery in high-energy physics is that `the party's over'."
Frank Yang, 1980
[+] [-] pbhjpbhj|7 years ago|reply
Michelson (of Michelson-Morley fame), apparently, IIRC. I'd warrant that despite his credentials Yang (of Yang-Mills fame) is making a similar mistake.
But I do think we're likely to see a retarding of the pace of change in fundamental physics (I think we're on to a reflective phase, where science consolidates, and social change progresses; leading to more focus on higher-order sciences - biology and such).
[+] [-] empath75|7 years ago|reply
[+] [-] peterlk|7 years ago|reply
[+] [-] v_lisivka|7 years ago|reply
[+] [-] czbond|7 years ago|reply
[+] [-] sprash|7 years ago|reply
Actually, we are now going from a boring phase of particle physics where the theory was able to predict anything we were able to measure afterwards to a phase where no theorists has a clue what might happen.
This phase is called "exploration". It consists of many "blue shots" of which many will probably have zero results but have to be done in order to find out what is really going on. Theorists had a good run with prediction, now it's the experimentalists turn to lead the way with exploration by producing new data.
When the Muon (basically a heavy version of the electron) was first discovered it 'seemed so incongruous and surprising at the time, that Nobel laureate I. I. Rabi famously quipped, "Who ordered that?"'[Wikipedia]
The new CERN collider has got to be build. To risk to miss the next great "Who ordered that?" moment would be grossly inconsequential.
[+] [-] blueplanet200|7 years ago|reply
There are many, many, MANY papers that fly out of these particle physics experiments. Most of the papers are about how they do not find stuff.
These papers take the form: "Search for the pair production of X in proton-proton collisions at s√ = 13 TeV" or other more generic papers where they just look for anomalies against Standard Model predictions. Fun fact - nothing found yet! This was the case at the Tevatron, where countless experimentalists poured over the data trying to find the slightest hint of something new. It also is the case today (so far) with the LHC.
To suggest that we're in a new phase where we're going from a "boring" phase to a new one where theory doesn't know kinda misses the point that experimentalists have already been doing this.
[+] [-] Anon84|7 years ago|reply
While I am a theoretical physicist by training, I have no doubt that those same billions could be much better used by many other fields such as biology, chemistry, computer science, ai, etc...
[+] [-] jgoodknight|7 years ago|reply
[+] [-] Filligree|7 years ago|reply
Yes, a larger collider is unlikely to find much, but it's cheap enough that we should do it anyway. As bets go, it's a good one.
[+] [-] pera|7 years ago|reply
https://home.cern/news/press-release/cern/new-cern-facility-...
https://www6.slac.stanford.edu/news/2018-11-28-future-fighti...
[+] [-] api|7 years ago|reply
[+] [-] _cs2017_|7 years ago|reply
It seems the field has advanced so far that EVEN IF new discoveries emerge, they would be of no practical value.
I'm not saying it's not interesting (I like reading about it FWIW), and I'm not saying it will never ever prove useful. But from resource allocation perspective, tens of billions of dollars required for high energy experiments seem to be much better spent on other areas of physics. That is, until the civilization advances far enough that understanding the depths of particle physics or cosmology becomes relevant.
[+] [-] hashkb|7 years ago|reply
Particle physicists would disagree. A complete understanding of quantum mechanics, squared with general relativity, is very likely to have practical applications.
Cliche analogy: if you thought the world was flat and ships were falling off the end of the ocean, you might be investing your money in world-edge-detection; and you might say there's no point in studying the edge of the world itself because no practical value can come of it. You wouldn't have any idea that circumnavigation was (relatively) easy once you understood more about the nature of the world.
[+] [-] graycat|7 years ago|reply
[+] [-] chimprich|7 years ago|reply
[+] [-] empath75|7 years ago|reply
[+] [-] raverbashing|7 years ago|reply
We're not even sure if there's anything in those higher energy ranges, there are certainly knowledge gaps, but maybe a bigger collider is not the answer. At least not until we have some other hints and new theoretical ideas.
[+] [-] kakarot|7 years ago|reply
If we're hitting a wall with respect to increasing energy in a system as much as possible, maybe we should make sure we've picked all of the low-hanging fruit from decreasing energy in a system as much as possible.
[+] [-] dwaltrip|7 years ago|reply
A few examples: QFT and GR are not integrated, dark matter, dark energy, the vacuum catastrophe, and so on...
One could make the argument that a larger collider is not the best way to attack these (I have no idea), but that is a different statement.
[+] [-] archgoon|7 years ago|reply
If the funding for your field is predicated on building a larger collider to discover new particles; then you're in trouble. That is the sense 'Particle Physics may be done' is meant in this context.
[+] [-] AnIdiotOnTheNet|7 years ago|reply
[+] [-] ForHackernews|7 years ago|reply
[0] https://en.wikipedia.org/wiki/Neutrino#Mass
[+] [-] T-A|7 years ago|reply
He also didn't include quarks, so by the same logic, the "standard model" is inconsistent with those too.
[+] [-] FreeFull|7 years ago|reply
[+] [-] Mugwort|7 years ago|reply
[+] [-] vertline3|7 years ago|reply
[+] [-] zwaps|7 years ago|reply
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[+] [-] unreal37|7 years ago|reply
[+] [-] Mugwort|7 years ago|reply
[+] [-] Sniffnoy|7 years ago|reply
[+] [-] OscarCunningham|7 years ago|reply