New exotic matter particle, a tetraquark, discovered at CERN | Hacker News Reader

New exotic matter particle, a tetraquark, discovered at CERN

phys.org

555 pointsmherrmann209 comments

> The new particle contains two charm quarks and an up and a down antiquark. Several tetraquarks have been discovered in recent years (including one with two charm quarks and two charm antiquarks), but this is the first one that contains two charm quarks, without charm antiquarks to balance them.

This is not the first time a tetraquark has been measured, but instead it's the first time a tetraquark with two charm quarks and no charm antiquarks. That's still nice work, but I was initially confused by the headline ("didn't they discover those already?").

I read it as: "CERN has discovered a new particle, and that new particle is an instance of a known class of particles called tatraquarks". The wording is a little sloppy and ambiguous, but headlines are pretty tightly constrained so I'm willing to cut the writers a little slack on this. I've seen much worse.

"Quarks are the fundamental building blocks from which matter is constructed."

I sometimes wish would include "In our current model", "We now think that", or some other qualifier.

Such absolute statements have been made frequently prior to our current understanding.

I have no special knowledge to lead me to believe that quarks are not the end all of parties.

But I was happy with atom being the fundamental thing, and then electrons, neutrons, protons were the thing as well.

The other day I read about Fractons "quasiparticles or Partial Particles", so now I have to figure those out as well.

I have lost track if the graviton has been found yet. I dont think it has.

From a purely layman's sense of esthetics the current model for particle physics is messy and a little spooky.

I have an odd hobby. I collect old paper encyclopedias from pre 1970 For every language that I speak. It takes up MASSIVE amounts of space.

The oldest I have been able to acquire on a limited budget Is 1880.

It is always fun to track concepts over time.

They all state what the world is like, and how it works as bombastic facts.

Yet over time, most of it gets replaced or at least highly refined and things are removed.

Particle physics is an active field with much still to learn or figure out. Let us keep that in mind.

"We now think that" is the qualifier on the entirety of physics. It's redundant.

I'll certainly give the authors of the papers the benefit of a presumption of humility; it's the people "translating into layman's terms" and "passing on knowledge" that introduce Authority, and other errors, as part of the process.

"Think for yourself, schmuck" is the only dogma worth petting.

Haha. True. Some parts of physics are way shakier than others though. For example, the whole big bang, dark matter, dark energy area needs the qualifier of, "We know we've got something wrong here, but its the best we've got". (eg see https://en.wikipedia.org/wiki/Big_Bang#Problems_and_related_...). I'm trying not to be controversial here. I'm just using this as an example of physics with well known problems.

Regarding, "Quarks are the fundamental building blocks", do we actually think that? If so, why? I'm genuinely curious. Is it just because we haven't seen anything more fundamental? That would violate your "We now think that" qualifier - ie if that is the reason, the qualifier should be "We have NO reason to think that...".

There is a theory about Preons.

This theory has fallen out of fashion.

"In particle physics, preons are point particles, conceived of as sub-components of quarks and leptons."

https://en.wikipedia.org/wiki/Preon

It's much worse than you think.

In physics there is 1) we know this is definitely wrong but it's useful and 2) this is very right so far and it's probably going to be wrong. I'm only a little bit joking. Now, I am not a physicist but I have been in a physics rabbit hole for a few months now.

The absolute best most experimentally verified theories we have are: general relativity and quantum mechanics. These are the pinnacle of physics. And they are incompatible with each other. So we know for sure that one is wrong. Or both are wrong.

String theory might be the resolution of that, making strings the most fundamental thing. But we've been working on it for 50 years with basically nothing to show for it so far. And there may be more beyond strings, who knows.

Of course there are many things in physics we can say with great confidence. But in terms of fundamental understanding there is ONLY "we now think that".

If only epidemiologists had such humility

> I sometimes wish would include "In our current model", "We now think that", or some other qualifier.

There is actually good reason to think quarks aren't fundemental. Even ignoring the empirical shortcomings of the standard model (specifically the incompatibility with General Relativity), it just doesn't "look" like a fundemental model.

Specifically, it is essentially a periodic table of elementary particles, with 3 "generations" of matter particles. Like the periodic table of the elements, this structure is highly suggestive that there is some deeper underlying structure.

I agree that we don’t know. But there is also evidence that quarks are fundamental. Based on all our measurement, they are point like particles with no internal structure or size.

Sure, but where did the word "atom" come from?

Perhaps the structure becomes visible at higher energies?

Two more technical treatments:

https://cerncourier.com/a/new-tetraquark-a-whisker-away-from... https://lhcb-public.web.cern.ch/Welcome.html#Tcc

The article points to an ongoing conference as the source, unfortunately (despite having no registration fee) the live-stream is password protected for non-participants :(

https://www.eps-hep2021.eu/live_stream/

Edit: It seems the talks may be released, in the end

>We would like to record your presentation at the EPS-HEP2021 conference and make it publicly available via the INDICO page and the DESY media streaming server until one week after the end of the conference.

They probably don't want internet randos jumping in and flooding the chat with porn.

That makes sense for the zoom sessions.

But, although I've never run a conference, I naively can't see that broadcasting the plenary session's video a little broader (to the three to five latecomers likely to stick around!) would really cause problems.

Not to be a stereotypical "Concerned Facebook Taxpayer", but in general I'm really fond of CERN's transparency, and I appreciate all the work they do to keep science open. They're usually way ahead of the field and it's refreshing to see, I love following what comes out of the LHC data.

So all that to say, maybe I've set my expectations a little high when it comes to physics and public access =)

Many online conferences I've attended this past year have both a Zoom meeting for registered participants and a YouTube "simulcast" for people who don't care about asking questions. I haven't run one and don't know if the logistics are complicated; maybe the organizers just didn't think of doing it. Anyway, these days most conferences seem to be pretty quick at putting videos out, though of course our attention will be elsewhere next week...

>Such proximity in mass makes the decay "difficult," resulting in a longer lifetime of the particle, and indeed Tcc+, is the longest-lived exotic hadron found to date.

So... how long does it live?

The resonance width is inversely proportional to the lifetime, and if the resonance width is about 400keV, the particle would live for about 10^-21 seconds. For comparison, neutrons decay via the weak force in about 800 seconds, and delta baryons, a randomly chosen strong force decay, live for 10^-24 seconds. That makes this tetraquark long-lived for a strong decay, but that's way, way faster than a weak decay.

https://en.wikipedia.org/wiki/Resonance_(particle_physics)

So not usable as spaceship fuel

If you're allowed to use something produced in an accelerator as your fuel you can't beat antimatter, which is as stable as normal matter until Kirk orders warp one.

There's always many considerations. Energy density, stability, what kind of energy can you convert it to, can it be directed easily, how hard is it to store etc...

Antimatter's reputation for being incredibly difficult to store comes from the fact that it's produced as individual particles. A superconducting antimatter hockey puck would be much easier to store than a cloud of antiprotons of the same mass.

And yeah, you'll need a way to build gamma ray mirrors before antimatter reactions will push you in any direction (the energy comes flying out isotropically and we can't presently do anything to stop or direct it), but we can cross that parsec when we come to it. :-)

Gamma ray mirrors sound like they’d be extremely useful for nuclear power too.

Superconductors pretty notoriously need to be kept cold, which adds another difficulty of cooling the antimatter without touching it

If it was surrounded by a cold mass that it could radiate photons to across a vacuum, its equilibrium temperature would be that of its container.

For now. By the time anyone could even possibly create enough antimatter to matter (heh), critical temperatures should be much higher. The record is broken fairly commonly.

I would be so nervous to be in the middle of space with an hockey puck of antimatter.

I guess I'd be just as nervous in space with thousands of tonnes of explosive propellant. Spaceflight always operates on the very edge of what's possible, not of what's safe.

I think that's what the dilithium crystals are for. ;D

Presumably antimatter would be your energy source, but not your propellant. The gamma rays from a small number of annihilations would heat up a much larger amount of normal matter.

At least for the first generation, you likely also wouldn't be using antimatter as the main source of energy, but rather as a method of initiating some other reaction. For example where in a conventional fission reaction you get a relatively clean split of a nucleus into two halves plus a few extra neutrons to drive a chain reaction, an antiproton will blast apart such a nucleus like a billiard break, allowing fission reactions with much less than a conventional critical mass. A quick burst of positrons hitting the surface of some lithium deuteride would be able to replace a fission primary and make a pure-fusion explosion. Either of these options could be used as either incredibly low-mass nukes for an orion drive or as a light weight reactor for a more conventional nuclear propulsion method. While about 600 times less energy dense than pure antimatter, you're still talking 10 million times better energy density than our best current rocket fuels, while using several orders of magnitude less antimatter.

I like black holes because once you have one you don't need an accelerator for refueling. https://arxiv.org/abs/0908.1803

Huh, "black holes move when you push them" is interesting. I suppose you could feed it with a beam, but focusing a beam down to attometer-size beamwidth seems like the hardest part, ignoring making a subatomic black hole in the first place. But sure, I suppose capturing the radiation and redirecting most of it back into the black hole to push it and maintain its size, and just enough spare to push the ship itself at the same speed is feasible. Feels like a "free energy" invention but I don't see where it fails, especially if you could capture the majority of the radiation and feed it back into the black hole directionally, minus whatever used to accelerate the rest of the ship.

I see, after more thinking, redirecting the radiation into the black hole would push the ship backwards with equal energy, so half the energy needs to be reflected back into the black hole at the correct direction, and the other half needs to shoot out the back as exhaust, and you'd need additional mass to prevent the black hole from shrinking and getting hotter.

They seem to conceptualize a ~100-year black hole which balances semi-feasible mass, power output, and lifespan, which is radius 2.7 attometers, 1.8 million tons, and 17 petawatts (!) of power. Looks like the saturn V was about 50 GW of power, so having ~500,000x the power, with only less than 1000x the mass (2900 tons vs 1.8m), means this thing would propel at hundreds of G's of acceleration, unless the ship itself was another 500 million tons? It looks like the WTC towers were "only" about 500,000 tons, so if you wanted to drop the acceleration to something survivable by humans, you would either need a much larger, colder black hole, or a ship of proportions of 1,000 WTCs.

The 10-attometer black hole, with "only" 1 petawatt of power and mass 6.7 million tons and lifetime 5,000 years, seems more reasonable, you'd want a ship with mass 58 million tons to have Saturn V levels of acceleration, only 100 WTCs and the black hole is still only about 10% the mass of the ship. Still, this is only about 6x the width of a proton where we're trying to beam on the order of a petawatt. We would probably need a lot of lasers packed densely together near the back of the ship to focus together on this point to avoid the beam itself being near capable of creating black holes, all coming from the same direction where we need to exhaust equally (or more) as much power to get the ship to keep up with the black hole.

Next step would be to figure out how big of a net we'd need to collect enough mass to maintain the black hole but I've spent enough time on this already.

Alcubierre drives almost seem more reasonable than this, almost.

Oh, and the temperature of this thing would be around a trillion degrees, pretty sure most of that radiation would be gamma rays. Need to figure out how to reflect gamma rays with efficiency. This is apparently around the temperature of a SMBH's accretion disk, the temperature of a new neutron star, and the temperature where matter doubles in mass due to relativistic effects.

All this being said, if we can balance the mass of the black hole with that of the ship, with a black hole with lifetime 5000 years, and we achieve 1g constant acceleration, we can cross the galaxy in 24 years and park it for up to a few thousand years before needing to feed it to prevent it from getting too small/hot. https://en.wikipedia.org/wiki/Space_travel_using_constant_ac...

Imagine if you could see the other side of the galaxy and make it back to Earth before you turn 50 (though Earth will have experienced 200,000 years), or, since once you're already at such relativistic speed, see Andromeda and come back before you're 60. Apparently we could round trip to the edge of the (Earth's?) visible universe in right around 100 years. Of course, by time you made it back, Earth would be 26 billion years older, the sun will have exploded, etc. Of course, if these are drone ships, we don't need to worry about human-survivable acceleration, and we could retrieve data much faster, but then no biological lifeform would have been there.

This was such a cool read, thank you!

What is hardest for me to comprehend is probably the last part about time being relative. All this stuff makes me think about how everything is made of the same matter and then, what am "I"?

Btw this part from the wiki link cracked me up "Constant acceleration is notable for several reasons: It is a fast form of travel."

Power scales to the square of exhaust velocity while thrust linearly, so if you have a very good power to weight power source like a black hole, you can use a very high exhaust velocity and thus can get by with very little reaction mass. Which is good.

Also, you can make a spaceship out of an asteroid (or from asteroid materials) so multi WTC mass is not a problem.

I see. I was assuming we were thrusting with nothing but gamma radiation, which is the speed of light, unbeatable, but I see with such small black holes, we may end up with some matter evaporating from it. I suppose that's one more benefit to larger, colder black holes: more likely to have lightspeed radiation than massive particles.

We could go for something closer to the temperature of the sun / wavelength of green light, about 10^19kg, easy to reflect, but that's about 0.1% the mass of the moon and would only output about 3.5 microwatts. Could try to balance between an amazingly reflective mirror to EUV or shorter wavelengths, which is more physically realistic than reflecting gamma rays, and usable power output, but that's simply out of reach at the moment. I wonder if we had an atomically smooth mirror, the smallest wavelength we could reflect with efficiency, and thus the highest power black hole we could use. Maybe it makes more sense for the black hole to have much higher mass than the spaceship, but 1g acceleration will be difficult.

Looks like most atoms are about 0.1nm, so 10^18kg black hole, for 350 microwatts. Like turning on a laser pointer attached to the moon and expecting usable thrust. Still far too large and not powerful enough to be a useful power source like a a 10^8kg black hole for around a petawatt. Either we figure out how to reflect deep gamma rays or it won't happen.

Needs to be a very short trip.

Are these decays equivalent to drops to a lower energy state where that energy is mass?

The term "lower energy state" is a funny one, because isn't energy conserved? What's happening is a drop to a more spread out state, where you have several particles making great time flying away from each other instead of one high-energy-density locus in the center.

Edit: Just to clarify, the time-variant system exception does not apply in this case. It really is an entropy thing, moreso than an energy thing (which is constant in every particle decay that happens on Earth.)

Fun fact: in the most general case, energy is not a conserved quantity.

https://www.preposterousuniverse.com/blog/2010/02/22/energy-...

Isn’t information a better unit?

MengerSponge's article is raising an extremely subtle point about how we translate modern physical theories into English: we do it poorly.

Conservation laws (Noether's theorem) are dependent on the way the physics is voiced, mathematically. Saying "energy is conserved" is the moral equivalent of looking at Newton's laws and just ignoring GR. GR tells us new, precise, and amazing things about conservation laws. It's just that, unfortunately, they're a little hard to translate into English.

>Saying "energy is conserved" is the moral equivalent of looking at Newton's laws and just ignoring GR.

If you're not expecting the spacetime background to be changing rapidly during your experiment, it's pretty moral to say energy is conserved.

By Noether's theorem as long as you don't have the laws of Physics change over time then energy will be conserved. The problem is that the definition of energy changes when you model a different system or change the way you model an existing system (ie Newtonian -> GR). A follow up problem is that the energy definition that results from applying Noether's theorem can get hard to translate in plain English.

my friend that thinks if he plays the breaks properly on his EV he generates energy, will be happy very hear this.

All he has to do is push his Tesla to the top of the hill!

The idea that spacetime itself has energy, which balances out the apparent lack of energy conservation in matter fields, is a far stronger interpretation than the article suggests. Spacetime energy bends spacetime, which is why gravitational waves exist. It's even called the stress-energy tensor.

This is lovely. Wikipedia sent me from energy not being conserved, to time translation symmetry breaking, to time crystals as a source of perpetual motion.

Just need to find a tie-in to 5G and I can write my own time-cube parody website.

(The article is also very interesting, of course!)

Despite free neutrons decaying in 800s, there are many stable elements containing neutrons. Would it be possible to imagine a tetraquark as an ingredient of a stable particle?

No. The presence of a valence antiquark guarantees it will decay at some point.

That’s not the full explanation; the antiproton is stable (or, is as stable as the proton).

It’s that the net baryon number is 0 and that the flavor ‘quantum numbers’ aren’t conserved by the weak force. If you could turn off the weak force, this cc ubar dbar tetraquark would be absolutely stable.

Then I wonder if this "particle" is just some components that takes 10^-21 seconds to bounce away from each other after colliding?

They don't just "bounce away", some of its quarks turn into different ones through interactions, and that is enough to class that process as a decay.

Also, quarks can't bounce away from each other. Lone quarks do not and cannot exist in nature, as far as we know.

Fun fact, the reason strange quarks are named strange is because when we discovered the first hadrons containing those quarks, they were strangely long-lived.

Long-lived here meaning 10^-10 seconds, instead of 10^-20 seconds. A whole tenth of a nanosecond!

That is actually quite a long time at the quantum scale.

The article (light on details, as usual) mentions that a slightly different configuration of a tetraquark would be very stable (again, not sure if that means nanoseconds or hours). If such stable multiquarks exist, without an electric charge they would be effectively untraceable, right? The only way to see such a particle would be to hit it precisely with an even smaller particle and get it to bounce back.

The more likely (I'm not a physicist) is to watch the decay of the particle and trace it back from there.

>The only way to see such a particle would be to hit it precisely with an even smaller particle and get it to bounce back.

Bounce back from what force? Whatever forces would make it interact with a single particle would make it interact with a detector, which is itself made out of particles.

They say the extra-stable tetraquark would only be susceptible to decay via the weak force, which means you'd have to wait around until it decayed, and then you'd often be able to see some charged remnants.

Can such tetraquarks form semi stable macroscopic structures like atoms? For example, if they aren't completely neutral, a group of them would be able to maybe attract an electron and become a quasiatom of some sort.

The stable-to-strong-decay species they're talking about, bb anti-u anti-d, would have a charge of (-1 -1 -2 -1)/3 = -5/3 times the electron charge. I guess its antiparticle would be positive, so maybe an electron could hang around for a while. I don't know how long that tetraquark is expected to live, though.

The charge would actually be (-2 + 1 - 1 - 1)/3 = -1 of a proton's charge. There isn't any physically viable combination of quarks that would produce a non-integer charge. The article mentions the bb tetraquark can only decay through the weak force, but I'm not sure how long it'd live either.

I don't think that's a unique property to tetraquarks. Neutrons or neutrinos also are not electrically charged. I'm not sure what you mean by untraceable, but neutrinos rarely interact with other particles and many, many of them pass through you every second without you even noticing.

A stable heavy-quark tetraquark shouldn't live longer than, say, the B_c meson, which has a lifetime of about 5×10^-13 s

I recently finished The Three-Body Problem and The Dark Forest, which explore the concept of aliens using their super advanced technology to mess with the results of Earth's particle accelerators, thereby stopping humanity's ability to develop technology based on new physics.

Is this discovery exciting? Or are we living in The Three-Body Problem?

Interesting.

For what reason are the aliens trying trying to stop us from discovering new physics? Stop us from blowing ourselves up? Blowing them up?

Without ruining too much of the books (they are worth a read), there is conflict between us and the aliens and limiting technological progress is an important part of their strategy

The aliens are coming to Earth to take it over. They aren't much more advanced than us and so don't want us to be more advanced than the fleet that arrives (it takes them a few hundred years to get to Earth).

If aliens don't like us, then why wouldn't they just destroy us, rather than troll our physicists and mess with the results?

Why would they specifically mess with the particle accelarators at this point? Why not with earlier physics?

Because they're hundreds of years of space travel away so they send sentient protons to sabotage our particle physics so that we can't develop advanced enough technology to stop them by the time they arrive.

While the entire series is absolutely incredible, I _loved_ the premise of human beings knowing 400 years in advance that aliens are coming. Such a fascinating start to the trilogy.

Here’s a possibility: They are in the next universe over, and so far the only thing that passes between is gravity. Fine-grained control over gravity could allow them to mess with things but not destroy us (if they even wished to. I don’t even think Earth would vote to destroy an unknown civilization if the roles were reversed)

maybe we are their toys, or maybe our emotions is their energy source

In the book that's the state of human science when they learn of our existence. Also, they want our planet and it will take them a long time to get to earth - so long in fact that they predict that if our physics is allowed to mature they won't be able to beat us militarily by that time. They need to stop progress asap.

Spoilers below:

The Three Body Problem trilogy breaks down if you think about it too hard. The in-universe explanation was that the aliens did want to destroy us, and had an attack fleet heading towards us. However, the attack fleet was relativly slow, and they were concerned that by the time it reached us we would have advanced to the point where we might win in a fight. To prevent this, they sent smaller probes to us at near light speed. In theory, these weren't capable of causing significant damage, but they could cause enough of an effect that they could make the results of particle accelerators useless. Without being able to use particle accelerators, we wouldn't be able to advance our knowledge of fundamental physics, so the aliens were confident that when their attack fleet reached us we would be defenseless.

By itself, what I have written is not particularly absurd, but if you look at the other things those advanced probes ended up being able to do, they could have easily just killed everyone.

Killing everyone is too much to ask, remember they were ultimately just protons, physically they're not more powerful than cosmic rays.

Their strength was information gathering and special effects.

Protons that could cause controlled visual hallucinations in people. If they can cause that level of interference with our nervous system, they can kill us. Even if they were somehow limited to visual hallucinations, a well timed hallucination is easily lethal. They probably ought to be able to hack into computer systems with that as well.

Tbf, from the way they were described it should have been fairly easy to defeat the Sophons even without any science-fiction technology; just build e.g. 10-20 particle accelerators distributed over the world and take measurements close enough in time to each other that you cannot be at multiple sites without exceeding the speed of light. Then at most 3 of them could be corrupted for any given run, and these can be thrown out as statistical noise.

I think the argument was that they could send Sophons faster than we can build particle accelerators.

This is addressed in the book; a new sophon is cheaper than a new particle accelerator.

Totally agree with this, the effort to retard development could have been better spent with a myriad of ecosystem destroying actions or geopolitical manipulations. Also just send the indestructible probe to kill every human...

My bigger problem with this book was that the author seems to wholely confuse secrecy for strategy. The entire conceit behind the wallfacers seemed ridiculous to me. The best strategic plan need not be secret (eg MAD). Make it clear that humanity will destroy every planet in the solar system and you've got at least MAD in the centuries the trisolarians will take to arrive.

They cared about our stable single sun more than planets. We were not on the level to destroy our sun, or the planets themselves

More spoilers below:

They actualy did a fair amount of geopolitical manipulations. That formed most of the plot.

In the end, it turned out to be MAD that saved us, but setting up the MAD scenario involved secrecy from them (or else they would have stopped us before we could trigger it), and from the rest of humanity (because an official plan to destroy Earth would never have been approved).

It seems like the manipulations were exceedingly silly. It seems like having the sophont start a nuclear war would be straightforward. It was hard for me to suspend disbelief in the sense that it had planet-sized computational power and the ability to manipulate some information on the subatomic level, but couldn't find a vulnerability in aging nuclear launch protocols? The history of near misses with human controlled nuclear weapons suggests a variety of vulnerabilities exist that wouldn't require e.g. directly hacking into command and control. Could it spoof images/data to a sub? Could it cause hallucinations in a large sensor array that feeds data to Norad or a Chinese/Russian equivalent?

Re MAD: I think a plan to destroy Earth would have been easily approved - much like it was in 1960-now, with ICBM and SSBN retaliatory strike capability. Obviously somewhat different in that those MAD-based nuclear wars would be extinctive but not deny the planet to the trisolarians, but the idea that human governments aren't ready to commit to that seems wrong given our history.

The aliens specifically wanted Earth because of its life. A nuclear war would damage the planet's ecosystem too much.

> In the end, it turned out to be MAD that saved us

Read the rest of the series and this answer gets more interesting. I will not say any more about the outcome (spoilers)

The sophons don't seem to be able to do anything much beyond bother particle accelerators. The later droplet probes _are_ very nasty, but it's at least implied that those weren't even available at the time they set out.

Because your interstellar equivalent of the CIA can obtain the political capital to prevent a civilisational rival from emerging via subtle manipulations, but it can't obtain the political capital and consensus needed to commit wholesale genocide.

There's a big difference between the scenarios.

In this case the subtle manipulations were just a holding pattern while they waited on the genocide; it was going to take them 400 years to get here.

Maybe because we're their big brother tv show or just their zoo

Haven't read those specific books, but "keep the species at the level they were when discovered for preservation" is a very common trope of such things, and usually mapped on how humanity considers that "preserving a species" means keeping it exactly as they were when first discovered.

If you insist on looking at it from our perspective, how about curiosity? Let's see how far they (us) keep trying to make sense out of this nonsense. Trolling in the name of science I guess.

People from North Sentinel Island might ask themselves the same question about us.

I troll people I don't like all the time

It’s a great book, but it suffers from the same old issue. A civilization that is capable of packing a robot into particle by manipulating higher dimensions doesn’t need to take our planet. They could terraform Mars or any other planet they want.

Perhaps we look to be an exceptional vacation spot, and there are space Karen's who desire an "all natural" planet instead of a terraformed one.

iirc the solar system contained the closest planets, which is why they chose it. I don't think it matters if they want mars or earth, there's no way we would let them do that (send a massive military fleet definitely just to mars). they wanted to ensure their technology remained superior by the time they arrived

I had the same problem with the books. If the sophon is that omniscient and that powerful, it could do far more than just mess with experiments.

I also never understood the wallfacers - why can’t they communicate via encryption, using a private key stored in each individuals mind alone?

How would you use that private key without it 'leaving' your mind?

The same way you use a private key in a computer without transmitting it?

So how are you intending to do those calculations in your mind?

By being a super-advanced space alien?

I mean, or just practicing. Humans who put in the time can do pretty amazing stuff.

There is a section in the novel Cryptonomicon where the protagonist is in a jail cell and monitored 24/7. He communicates with another person via a deck of cards, with all of the cryptography performed in the two people's minds. It's annoying to do but should certainly be possible if the fate of the world is at stake.

The sophons are not that powerful and have very limited capabilities. Humans perceived as being very powerful because we doesn't understand how they work and they are being used to frighten us. It's like showing a gun to someone who doesn't know what a gun is. The limitations such line of sight, range, limited ammo are not immediately obvious. It looks as though you have a god-like ability to strike anyone dead by wishing it.

The sophons aren’t particularly powerful, though. They interfere with particle physics experiments by actually interacting with the particle beam, but they can’t do much else. It’s mentioned at some point that the humans are worried they could interfere with computers, but clearly they can’t even do that (if they could, Lou Ji’s plan probably wouldn’t work).

Why not just for fun? Like riding horses even though you have a car.

Or trolling.

  “Teasers are usually rich kids with nothing to do. They cruise around looking for planets that haven’t made interstellar contact yet and buzz them.”
  
  “Buzz them?” Arthur began to feel that Ford was enjoying making life difficult for him.
  
  “Yeah,” said Ford, “they buzz them. They find some isolated spot with very few people around, then land right by some poor unsuspecting soul whom no one’s ever going to believe and then strut up and down in front of him wearing silly antennas on their head and making beep beep noises.”

-- HHGTTG

Spoiler: It took them so long to get to earth that they were concerned about humans becoming a formidable opponent in the meantime. Had human advancement not been halted humans would have much faster access to Mars than they would.

True for what it is, but this is handled in the books. They literally don’t want our planet, they want our star.

And the dark forest: without a history of correlated interaction we have no reason to believe they will allow us to live, so we can’t allow them to live, so they can’t allow us to live.

Eliding a more major spoiler, they absolutely intended to annihilate us on arrival and they would have gotten away with it if it weren’t for, ah, “those meddling kids”. Everything else was cloak and dagger.

They definitely would have terraformed every planet in the system once they were sure we were gone. Or more likely deconstructed them, at that point in their development.

It's a good book, but while some elements are good sf it's not all hard sf. They're looking for a new planet and didn't even send a probe 50 years ago?

Because the trisolarans didn't know who was out there until they received a message from Earth. They were worried that if they sent a probe to another star then a more advanced civilization perhaps hiding around that star would see the probe arrive, trace the source and annihilate them.

> True for what it is, but this is handled in the books. They literally don’t want our planet, they want our star.

That's... an odd reason. There are plenty of stars out there, unless the aliens started out right next door (like in Alpha Centauri) there's not much reason to go after our star.

I haven't read the books...

> unless the aliens started out right next door (like in Alpha Centauri)

They did.

> unless the aliens started out right next door (like in Alpha Centauri)

Strongly recommended reading.

Well, the thesis is that with exponential growth and a modest amount of time there _aren't_ plenty of stars out there.

If you're growing that fast, then a system or two is a rounding error. You won't have plenty no matter what you do, so how about not wiping out other species for that extra smidge?

> unless the aliens started out right next door (like in Alpha Centauri)

This is where the aliens are (a trinary system). It still takes them 400 years to get to Earth and so they are trying to stifle Earth's technological advancements because 1) we know they are coming 2) our technological growth is faster than them (this is partially explained due to different biological and environmental factors. The aliens can't lie to one another and have environmental factors that frequently wipe out or pause their technological advancements). The aliens in question are supposed to be only a few hundred years (max) ahead of us technologically (or smaller than the difference in time that it takes them to get here)

They are indeed right next door. Also, it’s a crowded universe, and no-one wants to be noticed, so just showing up at Tau Ceti or whatever would be very unwise; there might already be someone there.

The major bit of artistic license is that their Alpha Centauri is way more broken than ours; the real one isn’t all that badly behaved.

It’s implied that the whole situation is very unusual; interstellar invasions don’t happen as a rule and they’re only doing it because their star(s) is basically broken.

Super spoiler below:

Their tri-solar system was too unstable to terraform, they needed a stable solar system to migrate to. Of course ours was the nearest with an habitable planet (otherwise there wouldn't be much of a story), so they can immediately colonize Earth, and probably begin the centuries-long process of terraforming the neighboring planets.

Oh great! I just started reading the book…

Still doesn't make sense. Why limit our tech when they ultimately want to just eliminate us all together?

Drop a super virus on us or irradiate the whole planet. Any species capable of disrupting our particle accelerators is more than capable of wiping us from existence.

It's kind of like nuclear warfare here on Earth. If you want to eliminate every living thing, then sure do some sort of scorched Earth type of thing. However, that leaves the planet in an un-inhabitable condition.

If you need to wipe out the inhabitants but leave everything else so you can now use it, you need to not destroy everything in the first place. Otherwise, you now have to terraform a planet that you chose because you didn't need to terraform it.

More spoilers:

In the book, they were scared of humanity's technological growth rate. They were observing our technological advances and noticed that it was significantly faster than theirs. While they were, at the time, technologically superior, they were afraid that after the 250+ years it would take for them to get to Earth, humanity would have become technologically superior; too strong for them to overtake.

That was probably the plan; but the “tech-blocking particle” gets here at the speed of light, ensuring that we are still sufficiently behind, technologically, by the time their e.g. virus or radiation gizmos arrive. It “freezes” development to ensure that they still have technological superiority when the much-slower, barely-relativistic, big guns arrive.

They could send the subatomic particles from Trisolaris to Earth at light speed, and then use the entangled pair of particles (one on earth, its mate on Trisolaris) to monitor events on earth in real-time.

As already said, that preserves the planet, prevents a potential enemy from further developing technologically, and enables real-time monitoring of and interference with that enemy's activities.

>and then use the entangled pair of particles (one on earth, its mate on Trisolaris) to monitor events on earth in real-time.

This, of course, breaks the known laws of physics, since lightspeed is a hard limit on the speed of causality. You can't use entanglement that way in the real world (if QM is anywhere close to correct)

The sophons themselves were a piece of magic science fiction. Which I think is fine because the author really doesn’t ask you to suspend your disbelief all that much throughout the books. The star plucking is another example, as far as we know you can’t use a star to do that.

But accelerating them towards earth “at the speed of light” isn’t exactly a problem. The LHC accelerates protons to about 3 m/s less than the speed of light, and as far as the plot is concerned the sophons travelling here at the speed of light, or some tiny fraction of a percent less than the speed of light doesn’t make any difference.

Right, that was the huge issue I had with the story. In most respects it seemed to be trying hard to be speculative hard SF in the Arthur C Clarke vein (i.e. fine to introduce exotic new physics, but only very carefully and consistently) so it was very surprising to have that gaping hole at the centre.

The aliens had instantaneous communications, and could directly influence events on earth, but still had to travel at sublight speeds? It wanted at least an acknowledgement of the inconsistency, and a token effort at explanation. As others have noted, it’s not at all clear why they couldn’t simply have killed off the humans remotely.

I can't reply to roywiggins for some reason, but it's possible that the solar systems are closer in other dimensions or something like that. Probably not though, because the higher dimensions are so small. I assume the author didn't think about it until it was too late, or they couldn't fix it.

The book makes the claim that the sophons they send over are very limited. It seems reasonable to surmise that they could not create a super virus. Yet they can disrupt sub-atomic experiments. We are talking about an advanced basically magic tech the author made up for the purposes of the plot. So the author can set the rules that the magic tech can do X but not Y.

They did also send weapons towards earth ahead of their fleet. They arrived much faster than their fleet, but much slower than the sophons.

an aside: i really wish hn had a redaction-style, click-to-reveal spoiler system. not that i don’t appreciate the spoiler warning here — it’s quite kind that people mark their comments as-such — but even when i’ve seen “spoiler warnings” for other content that i’d rather not be spoiled on, it’s very hard to not skim the next few proceeding lines out of habit (especially on mobile). i can’t imagine i’m the only one who does this.

.siht ekil meht etirw dluoc ew ebyaM

Let's see...

.stenalp gnirobhgien eht gnimrofarret fo ssecorp gnol-seirutnec eht nigeb ylbaborp dna ,htraE ezinoloc yletaidemmi nac yeht os ,)yrots a fo hcum eb t'ndluow ereht esiwrehto( tenalp elbatibah na htiw tseraen eht saw sruo esruoc fO .ot etargim ot metsys ralos elbats a dedeen yeht ,mrofarret ot elbatsnu oot saw metsys ralos-irt riehT

Oh god no, forget this.

There's also the weird aspect that [rot13'd for spoilers] gur fbcubagf frrz gb or noyr gb vasyhrapr naq dhrel znggre, ohg pna'g frrz gb ernq crbcyr'f zvaqf be xvyy gurz.

Gung'f abg dhvgr evtug, gurl qba'g npghnyyl unir gur znff gb rkreg zhpu vasyhrapr ba nalguvat

Gurl jrer cebgbaf, evtug? Fb gurl ernyyl pna bayl nssrpg guvatf nebhaq gung znff naq raretl enatr. Gurl pna zrff jvgu cnegvpyr nppryrengbe rkcrevzragf ohg pna'g nssrpg gur znpeb jbeyq.

TIL google translate doesn't do ROT13.

Spoilers ahead

It was such a letdown, the book starts great, and then the explanation turns out to be magical Alien proton computers? Yikes. It was so promising.

I eventually read the whole trilogy, I have very mixed feelings about it. It had some pretty cool ideas but it's hard to get past all the giant plot holes and outlandish fantasy. I guess you have to be in the mood to constantly brush off the bad parts (and boy there are many) and plunge forward.

A more materialist approach would be to say that it is the artists and authors of such books which are influenced by cosmos and the three body problem is an error detection code for repairing memory errors in collective consciousness to prevent civilizations from repeating unpromising patterns of development which have already been simulated.

Thanks for the spoilers.

Spoilers.

There are a few parts of the book, according to the translator, that are done in the manner of a Chinese folktale, which he tried to translate to a different style in English. I'm no expert, but I got the impression the sophont chapter was in this category. It has this otherworldly silliness with the multiple attempts to create a sophont going wrong in different dimensions, calculated to fit the repetitive pattern of a fairy tale.

I think the thrust, which might be hard to read in translation, is this: we can't imagine the technology a superior alien species would come up with, so it's related as a fairy tale beyond technological realism.

Anyway, I doubt it was meant to be hard sci-fi.

> Anyway, I doubt it was meant to be hard sci-fi.

Which was extremely disappointing, given that it was billed as such by many, and until the aforementioned mumbo-jumbo was doing a seemingly nice job on that front.

There where some good ideas in it but it never really worked for me, I have often wondered if it was translation issues.

The whole book is fun and creative fiction. Just enjoy it like you would enjoy any non-real TV or movie.

If you haven’t read the series, saw the spoilers here, and are no longer thinking about it… don’t get discouraged. Pay off in Book 3 via the space concepts are worth it still. Mind blowing fun stuff

Human story tellers are very attached to humanity, so the stories tend to anthropomorphize aliens. Most alien stories rehash old religious and hero stories. What do we have to offer aliens? In the category of vague as well as less is more, Arrival/Stories of Your Life and Others are about as compelling as it gets - humanity hasn't yet achieved full potential, going further out on a limb is folly (however entertaining it might be, it becomes less compelling).

The more truly alien, the less in common we have in all respects, the more boring that story turns out to be because? We're a selfish, self-interested, loathsome species who consistently overestimates its importance. The more different a fellow human is, the vast majority of people reject that individual because of their (weird) non-social behaviors.

So these alien stories strike me as deification, angels, devils, i.e. the supernatural, and don't adequately explain why or how any alien civilization would take interest in us, except via our own attachments to ourselves. This is central to good science fiction because they are stories ultimately about exploring something about humanity, it's not really about aliens at all. They're entirely incidental even if they seem important, aliens are just a literary device. But getting to science-non-fiction, a factual case of aliens, that's quite hard for most humans to imagine at all.

Consider how poorly most people coped with covid, and then consider how much more traumatic an alien visit would be, even assuming they were nice.

In Arthur C. Clarke's Childhood's End (1953) those aliens were "nice" but with a really big caveat. (And neatly explained devils.) But again, humans are the central part of that story, not aliens. It wouldn't and couldn't have been interesting to focus on the interests of the aliens without us being part of the story - we're just too self-interested by nature. The aliens' interests would have been boring to us, we just don't have the necessary common frame of reference with such beings. How could we?

This trilogy features long sections from the perspective of the Trisolarans without any humans around and their motivations are central to the plot.

Or perhaps the laws of physics that we observe are becoming more complicated over time, as a consequence of some deeper law of physics.

The simulation we all live in is getting a new patch with higher resolution models.

I wonder if we're in PROD, STAGE, QA or DEV? waves humanly

You spoiled it for me, I am on 1/4 of the first book :S

Oh blood, I just got this book. Is this a huge spoiler?

Don't worry, I'll just use a sophon to revert your memory.

It's plot-establishing, but not a huge spoiler.

Well, it kinda spoils some/most of book 1.

But IMHO the book 2 is the best and most intriguing anyways and that is totally unaffected...

Eh, it's hinted at, pretty early on. If you knew there were aliens in the book, I don't think it's THAT huge a spoiler.

No not at all. Keep reading.

Same. It's been on my list, but this is more detail than I wanted to see.

Rest easy, there is a lot more to the books than that.

In the books, the Sophons got in the way of the accelerated particle beam but somehow avoided being destroyed themselves. They wouldn't have allowed a new particle to be discovered.

They were destroyed but could bring themselves back together. The thing is that the particles are intelligent so could break apart in random ways that didn't match what particle physicists expected (they would then recombine outside the detector as to not be exposed).

In the Three Body Problem, the naughty aliens break reproducibility in particle accelerator experiments; they start giving random results. So we're good for now.

Unrelated to this topic, but Death's End is also a great book if you haven't started reading it. I can also recommend Ball Lightning which more or less takes place before the events in the The Three-Body Problem.

which book was better?

Why do these things take so long to find? Do they not show up in all collisions - why not, wrong matter, wrong speed? Do they regularly appear, but the "camera" has limitations? Is the "camera" all-seeing, but measurement interpretation inefficient? All/some of the above?

I think it's a matter of theory supporting observed data. They point the, "camera" at a bunch of experiments, which generates a ton of data, then it's up to theoretical physicists to explain the results. Once the results of a theory have been explained and then reproduced it stands on solid ground. I'm just speculating, of course. But that is sort of how astronomy works, at the polar opposite end of a similar field.

Your comment kind of implies that theorists analyse the data. (They don't even have access to it.) Analysis is the job of experimental physicists (like me) and can take years.

We don't wait until we have theoretical interpretations before publishing the discovery of a new particle. In fact, our results are kept confidential until the end of the collaboration's internal review process. In the absence of leaks, the first any theorist should hear of this new particle would have been the conference talk or press release.

Some physicists will get an idea for a new particle or decay mode. Then they will postulate various decay modes that could be captured by the detectors. The short-lived new particle arent directly detectable, but daughter particles may be. Particles leave characteristic signatures on the two large CERN detectors, each which consists of an onion of thousands of directional and intensity sensors. Then they computer search quadrillions of already recorded events at the detectors for a significant number of candidate events. This may take months for a postdoc or grad student to do.

I recall the Higgs had about 80-some possible decay modes. Only a handful of them could be measured above background noise. A couple of teams pursued two classes of them and found results.

> Do they not show up in all collisions

This is the biggest factor

> why not, wrong matter, wrong speed?

Quantum mechanics is probabilistic. The probability of these particular particles in these particular collisions is very small. So we need to do a lot of collisions in order to have a statistically significant signal.

> but the "camera" has limitations?

Sure. While we regularly upgrade our detectors or build newer, fancier ones, there will always be some limitations.

> but measurement interpretation inefficient?

It's certainly slow. It can take months/years to infer a result from the data. The major bottleneck is people. Even the thousands-strong armies of physicists who work on the LHC experiments would take decades to fully exploit the available datasets.

someone please ELI5 and how this discovery is important for furthering our understanding of quantum numbers

The laws governing the strong force are somewhat well-known at this point, but calculations involving them are difficult and in many cases beyond our reach. Furthermore the fundamental constants are not known to a very high precision. Both of these problems can be addressed by collecting experimental data about how these particles behave in real life, both to pin down the constants, and to accept or reject calculation techniques.

It won't improve our understanding of quantum numbers in general (a quantum number is just a discrete conserved quantity). The final paragraph mentions measuring the quantum numbers of this particular particle, namely its angular momentum and parity.

What is the charge of a tetraquark? Is it neutral?

A tetraquark is four quarks. There exist three -1/3e quarks (dsb), three +2/3e quarks (uct), and then their +1/3e and -2/3e antimatter counterparts. 1e is the charge of one electron. The stability of a tetraquark is mainly a color/strong force thing and the electric charge comes along for the ride. Stable atomic nuclei, which are held together by the strong force, go up to +83e and they still don't fall apart due to electric repulsion.

However, there is one constraint that might show up in charge. Tetraquarks always have two antiquarks, which is necessary for the color charge to come out to zero. Working out every possible combination is left as an exercise for the reader. :)

The highest possible charge is 2/3 + 2/3 + 1/3 + 1/3 = 2. Every swap of a quark to a lower charge one reduces the total charge by 1. So the possibilities are 2, 1, 0, -1, -2.

But a combination like 2/3 + 2/3 + 1/3 + (-1/3) = 4/3. Are these not possible?

That's not exactly two antiquarks.

This particular one is +1e but there are many other forms a tetraquark may be able to take.

https://trimread.org/articles/31

I came here to write something else. But after typing I felt it would be sort of bikeshedding. So did not add it. And now I am going to see if any other comments sound like bikeshedding. (including this one probably.) :)

Neat! What can you imagine might be applications for exotic particles like this? (even if if it's a stretch or fictional)

Given the massive energy required to do experiments like these and the microscopic scale in both physical and time dimensions I think we're centuries away from doing something practical with the particle itself. It may be the missing piece of some future technology we can't even imagine yet.

I think the more immediate motivation is to help either validate our current understanding of how the universe works, or to break the model in an interesting way.

In the world of double-open-heavy-flavour hadrons (to which this particular tetraquark belongs), you get bullshit headlines like this https://www.sciencealert.com/new-quark-fusion-releases-signi...

Does it fit into the standard model? I thought higgs boson was the last undiscovered particle according to the standard model.

You're referring to elementary particles. This is not elementary as it is composed of Quarks, which are part of the standard model and are elementary.

tetra-quark: 4 quarks. It's composed of particles that are already part of the standard model, just an a previously unseen arrangement.

Particles are compositional.

Normal human here, can someone speculate on potential industrial uses?

Too early for that, though does open up other science that may well. Might finally pave the way for gravity shields, food replictor...or nothing.

The aspect that this tetraquark breaks down into something with more mass will certainly be interesting for study.

Nobody expects noting. No reason to expect anything whatsoever.

The particle is incredibly short-lived, requires a massive particle accelerator to create, and is hard to detect.

This is just another high-energy physics experiment. The hope is that someday something comes out that does not fit into existing models and is a sign of new physics.

I wonder if the sophons from Trisolaris would have blocked this discovery.

I am unclear if they produced a tetraquark particle, or they simulated the particle.

> ... used Google’s quantum computer to demonstrate a genuine ...

I don't see a mention of quantum computers in the article. I think LHCb detected the particle.

Can someone explain the practical use for this? Better batteries or something?

Another tick forward in fundamental physics that will pay off as some theoretical framework getting slightly more grounded and paying off in a tangential way 70 years from now.

Congratulations for the discovery of the next epicycle!

Is this the one that makes all the Sci-Fi gadgets do the impossible? I need to know if I should be excited or not.

You just need to apply more quantum.

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