8 ms·
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, wh
by smallnamespace 8y ago
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.
- dkersten 8y agoInteresting. Thanks for posting this, it really helped me understand what the issue is.
- high_derivative 8y agoThanks for these insights! Do experimental (!) particle physicists have any other way of doing research on this than colliders?
- Balgair 8y agoOne possibility is in using space based detectors. Essentially, you put the detectors up above the atmosphere in a relatively 'neutral' area of space to avoid background from other sources [0]. Then, using this floating detector, you use other sources in the universe to do the colliding for you. Something like an astrophysical jet[1] coming out of a black hole, some neutron stars colliding, some super novae collapsing, etc. Taking all these detectors together, you can then get the results you want. The major issue is that you have nearly no idea when/where these events will occur, and they are really rare to begin with. Add the distances that these things occur at and your error bars go through the roof[2]. Still, over a VERY long time and with a LOT of these detectors spread about the Sol system (and likely a bit further out), you can get the results you'd need. It's not cheap or easy or timely. But with 12 orders of magnitude to go, it's a lot cheaper, easier, and more timely than trying to build an accelerator with Jupiter in the way :) [0] as in, not next to the Sun, Earth, Moon, near gravitational perturbers, etc. [1] https://en.wikipedia.org/wiki/Astrophysical_jet https://en.wikipedia.org/wiki/Astrophysical_jet [2] http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/lenseq.html http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/lenseq.htm...
- eanzenberg 8y agoThere are particles of 10^20 eV energy or more out in space you get for free. But how to do anything with them.. that's yet to be seen.
- Roverlord 8y agoI could have sworn I read yesterday that (I think it was Sag A*, or Cyg X-1) is literally pointing it's jets right at us.
- rmu09 8y agoBuilding more telescopes like LIGO, IceCube and a whole bunch of other "microphones" or "telescopes" or whatever you want to clal them. But not sure if that qualifies as "experimental" particle physics.
- fxfan 8y agoYou 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?
- zinclozenge 8y agoIt's probably helpful to think of this as phase transitions. At the plank scale "temperature" everything is mixed together, but when the system cools and undergoes a phase transition we start seeing different behavior. Sounds possibly like an invalid analogy, but in fact there's substantial overlap in the theories. If you want to read more try reading wikipedia articles on "ising model", "spontaneous symmetry breaking", "higgs mechanism".
- frutiger 8y agoIt turns out that seemingly distinct forces are related in some clever way. The most approachable example of this (though it doesn't quite extend to the other unifications listed above) is electricity and magnetism. Before Faraday's experiments, we understood static electricity (charged objects attract/repel charged objects of the opposite/like sign, proportionally to the product of the charge, and falling off with the square of the distance), and magnetism (magnetic poles repel). Once we saw that moving electric charges generate magnetic fields and vice versa, we opened the door to realizing that these are both just aspects of the same electromagnetic field.
- fxfan 8y agoThank you! That's probably the simplest possible explanation. "Related like electricity and magnetism are". How far is it from the "actual reality"? Would you (or anybody else) try giving a more difficult explanation?
- deleted 8y ago[deleted]
- stronglikedan 8y agoI 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.
- auntienomen 8y agoThis 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.
- Iwan-Zotow 8y agoMmm... Particulars of unification depends on how you extend SM, but general idea about unification at 10^16 GeV based upon EM/Weak and QCD coupling constants energy dependence taken directly from SM. Basically, if you plot those coupling constants vs log(E), you'll get their merge at circa 10^16 GeV. That's baseline and it is pretty much pure SM, details are filled differently from different GU theories.
- auntienomen 8y agoYes, but you need to assume there's a desert to get that result. Otherwise the renormalization flow is different.
- Iwan-Zotow 8y agoYes, I stand corrected, thanks
- cft 8y agoThe Plank scale (Grand Unification scale) comes from the simple dimensional analysis, that combines the gravitational constant with the Plank constant (and the speed of light). It doesn't not really depend on the details of a grand unified theory. It was fist calculated to be 10^19GeV in 1899 by Max Plank, well before any quantum field theory (well before quantum mechanics for that matter). Because it combines the Plank constant with the Gravitational constant, we know that it corresponds to the energy scale at which quantum phenomena unify with the gravitational phenomena. Currently the only theory that describes this unification is String theory, but as the op correctly noticed, it's far from any possible experimental confirmation. I was at a seminar of Alexander Polyakov, one of the founders of string theory, who compared the string theory to the knowledge of Democritus about atoms. He said that even though the atomic theory of Democritus was essentially correct, it was about 2,000 years ahead of any possible experimental verification. In his opinion this is how long it will take us to verify our Grand unified theory experimentally.
- mrfusion 8y agoThe 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.
- jandrese 8y agoIt would be tricky to anchor them in place so they don't wander out of alignment.
- mrfusion 8y agoWe keep gps sattelites in a very precise orbit. Maybe that can scale up? Also maybe the nodes could have some kind of magnetic ram scoop design to cover a larger area and funnel the particles through.
- jsjohnst 8y ago> We keep gps sattelites in a very precise orbit. Maybe that can scale up? Source for this? It was my understanding they weren’t, hence why the almanac data is so important, but I’m not positive that assumption is valid so I’d love a source to back up your claim.
- dmckinney 8y agoAlmanac is important for receivers to optimized what vehicles to track and when. The ground stations comment is the correct answer. https://gssc.esa.int/navipedia/index.php/GPS_Ground_Segment#The_Monitor_Stations https://gssc.esa.int/navipedia/index.php/GPS_Ground_Segment#...
- jandrese 8y agoWe aren't redirecting streams of high energy particles with GPS satellites.
- phkahler 8y ago
- mrfusion 8y agoDoes point 1. imply there’s a way to control the weak force via electromagnetism? (In theory at least) Kind of like how we create magnetic force with electric.
- seiferteric 8y agoI asked a similar question a couple weeks ago and was pointed to neutrino-lepton scatterings. If you search you will see an electron can interact with a neutrino.
- walrus1066 8y agoMinor 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 So you're guaranteed to then see 'new physics'.
- pdonis 8y ago> the relativistic mass of particles becomes so big that gravitational interaction is too strong to be ignored It's not relativistic mass that's the key factor: relativistic mass is frame dependent, and it's not the source of gravity. The relevant factor is stress-energy: energy density, momentum density, pressure, and other stresses. The key factor at the planck energy scale is that the density of stress-energy is high enough that we can no longer have confidence that classical General Relativity is an accurate description of gravity; we expect to see quantum gravity phenomena at that stress-energy density.
- walrus1066 8y agoI always understood that the Stress–energy tensor in general relativity has a momentum component, so two electrons whizzing past each other at near the speed of light would exert a stronger gravitational pull between them, in all frames of reference, than if the electrons were 'at rest', relative to each other? I admit I didn't study GR so happy to be corrected!
- pdonis 8y ago> I always understood that the Stress–energy tensor in general relativity has a momentum component, so two electrons whizzing past each other at near the speed of light would exert a stronger gravitational pull between them, in all frames of reference, than if the electrons were 'at rest', relative to each other? The stress-energy tensor does have a momentum component, but remember that all components of a tensor are frame-dependent. So is "gravitational pull". Obviously the trajectories of two particles passing each other at relativistic speeds will be different from the trajectories of two particles at are at rest relative to each other at some instant; but the difference is not quite as simple as "more gravitational pull", although the two particles having relativistic velocities does mean that the center of mass energy of the system is larger than it would be if both particles started out at rest. (Actually, the electromagnetic interaction between electrons is so much stronger than the gravitational that the gravitational effects are negligible in the scenario as you state it; but we could eliminate that issue by considering, say, two neutrons instead. My comments above assume that the scenario has been modified accordingly, which is why I said "particles" instead of "electrons".)
- OscarCunningham 8y agoIs 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?
- b_tterc_p 8y agoHow 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? Apologies if I am way off base
- frutiger 8y agoThere are lots of possible models of unification (a short list of where electroweak and QCD unify are listed here[1], not to mention many more models where gravity unifies), and without experimental data, we don't know which one is correct. 1. https://en.wikipedia.org/wiki/Grand_Unified_Theory#Unification_of_matter_particles https://en.wikipedia.org/wiki/Grand_Unified_Theory#Unificati...
- salty_biscuits 8y agoShould we be looking at these a bit harder? https://en.wikipedia.org/wiki/Ultra-high-energy_cosmic_ray https://en.wikipedia.org/wiki/Ultra-high-energy_cosmic_ray