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Physicists demonstrate existence of new subatomic structure
- sctb 10y agoWe've updated the link from http://sciencebulletin.org/archives/7339.html http://sciencebulletin.org/archives/7339.html to this, which looks like the original source.
- philipov 10y ago"On their own, neutrons are very unstable and will convert into protons — positively charged subatomic particles — after ten minutes. " ... "For the tetraneutron, this lifetime is only 5×10^(-22) seconds (a tiny fraction of a billionth of a nanosecond). " 10 minutes is an eternity and 5×10^(-22) seconds is closer to what I'd consider 'very unstable'
- Dylan16807 10y agoCompared to the almost-forever you can get inside a nucleus, or from protons, it's quite unstable.
- bonzini 10y agoInside a nucleus---yes; from protons, not really. Helium-2 is as unstable or possibly more unstable than the tetraneutron; lithium-3 and beryllium-4 don't exist at all.
- Dylan16807 10y agoThey will break apart, but the stability of the protons themselves is enormous.
- bonzini 10y agoYes, but the article is about multi-particle systems.
- Dylan16807 10y agoThe discovery is. The comment about neutrons decaying in ten minutes isn't.
- twic 10y ago> The research in Japan used a beam of Helium-8, Helium with 4 extra neutrons, colliding with a regular Helium-4 atom. The collision breaks up the Helium-8 into another Helium-4 and a tetraneutron in its brief resonance state, before it, too, breaks apart, forming four lone neutrons. I don't know how fast these particles were going in the experiment, but if they were going at the speed of light, then the tetraneutron would make it 150 femtometres from the site of the collision before decaying. By way of comparison, neutrons and protons are 1 - 2 fm across, and a uranium nucleus is 15 fm across [i]. So if the tetraneutron was actually going at a tenth of the speed of light, it would barely make it a nucleus's diameter away before exploding. [i] https://en.wikipedia.org/wiki/Atomic_nucleus https://en.wikipedia.org/wiki/Atomic_nucleus
- windsurfer 10y agoThat's not how relativistic speeds work. If this was going near enough to the speed of light, it could travel almost any distance before decaying. Time dilation would be observed of the particle, where it would appear that time is ticking slower for the particle compared to our own frame of reference.
- chunky1994 10y agoActually what the parent comment said would be correct. Time dilation and length contraction do not arbitrarily change the proper distances that particles travel at near light speeds. As observers, the detectors would see precisely what we expect if we calculate the distance using the detector's proper time when compared with the distance we experimentally measure.
- gpvos 10y agoYou forgot the sentence just before the last one. The weird thing is that they call the 5×10^(-22) seconds "stable for a period of time", but the 10 minutes "very unstable". >four neutrons together can form a resonance, a structure stable for a period of time before decaying.
- ianai 10y agoYou're adding context to "a period of time" that's not there. 1 ns, 1ms, 1 day, and 1 millennia are all "periods of time." As for stable vs unstable you have to contrast lifetimes across other particles.
- gpvos 10y agoOh, I understand that; I just think that in the interest of clarity they should have added a bit more explicit context. Now it looks odd.
- coldcode 10y agoPhysics is one science where the seemingly impossible winds up being possible all the time. Strange to think people spend a good portion of their lives studying things thought to not exist.
- 77pt77 10y ago>Physics is one science where the seemingly impossible winds up being possible all the time. Quite on the contrary.
- wyager 10y agoActually, physicists are desperate for an upset that will disprove the standard model. The standard model is, in many ways, too good, in the sense that it predicts most (but certainly not all) measurable phenomena to very high accuracy, but is not a complete theory. So we're looking for examples that break the standard model so we can figure out how to expand it to be complete, but we're having trouble finding useful mispredictions by the standard model. A few areas where the standard model is deficient: dark matter, matter/antimatter asymmetry, hierarchy problem.
- Manishearth 10y ago> where the seemingly impossible winds up being possible all the time. No, it's where the possible is often portrayed as impossible by popular reporting all the time.
- GavinMcG 10y agoI read the headline as "demand" and thought this was a rather petulant reaction to the "no new physics" development this year. https://home.cern/about/updates/2016/05/theory-theoretical-physics-crisis https://home.cern/about/updates/2016/05/theory-theoretical-p...
- agumonkey 10y agoStill no turtles.
- deleted 10y ago[deleted]
- ozzmotik 10y agoit's subatomic particles all the way down i tell you!
- jessaustin 10y agoI would have sworn I've seen an animation implying that at sufficient magnification the whole thing loops around to galactic superclusters. Non-intuitive, to be sure...
- andrewflnr 10y agoMaybe we just need a bigger particle accelerator to discern the turtle sub-structure of current known particles.
- TheRealPomax 10y agoMmm, scientific click bait titling. More accurate would be "Physicists demonstrate a theoretical subatomic structure in simulation". That's important, to be sure, but it has nothing to do with demonstrating the existence of a particle - we've determined something "should" exist based on simulation and data-interpretation plenty of times, and many of those have ended up being wrong. And that's good: good science comes from discovering what _isn't_ true, but that makes it all the more silly to have this title on the article. We've got the simulation worked out... now we need to see if it holds up to reality. It might not. If so, that's valuable information.
- jcoffland 10y agoApparently you didn't read the article in full before criticizing it. The article says that the simulation was used to verify real world observations from a particle accelerator experiment in Japan.
- johncolanduoni 10y ago"Verify" is a strong word. The RIKEN experiment didn't come close to the usual standard of evidence for declaring a new particle exists, it just showed a reaction for which creation of a tetraneutron is a possible explanation. There need to be a lot more experiments (different ones, not just repeats of RIKEN's) before anybody would be willing to declare tetraneutrons "exist".
- TheRealPomax 10y agoSimulations don't "verify" physical findings, they let us tweak the parameters under which we might encounter findings, and now we're not done: 1. practical observation (optional) 2. a hypothesis (either from first principles or to explain a practical observation) 3. testing that hypothesis 4. establish as theory if it holds up, or mark as "known to not be true" if it doesn't. You've not scienced until you're done with step 3, because step 2 on its own cannot "confirm" or "verify" anything found in step 1. The most important part is to confirm that a theory is not accidental, giving simulations a disadvantage: it is far easier to accidentally find parameters in a simulation than it is when you're on paper from first principles - even if that paper's Mathematica or R. You can always find some set of values, parameters, and functions that result in the thing you're looking for, so once you find such a set, you then still need to go back to the lab, verify that it holds up, and have others verify it holds up, too. (the result of a single study is merely a very interesting anecdote. It's not data until your findings can be reproduced, and it's not a scientific theory until it's proven to hold up. Until then it's just a hypothesis)
- maverick_iceman 10y agoThe original paper [1]. [1] https://arxiv.org/abs/1607.05631 https://arxiv.org/abs/1607.05631
- zer0gravity 10y agoI don't know, maybe this discovery has scientific value. But could it be the sometimes scientists report small "breakthroughs" just so that they keep the funding coming ?
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- poizan42 10y agoIs it really "subatomic" though? Seems more like it could be considered isotope 4 of element zero.
- johncolanduoni 10y agoTechnically subatomic refers to the size of an atom with electrons, not a nucleus (which is much smaller). It's especially appropriate here because neutrons aren't electrically charged, so their interactions with other particles are very short range.