Does Antimatter Explain Why There's Something Rather Than Nothing?

the most precious substance in our universe is not gold nor oil it's not even printer ink it's antimatter but it's worth every penny of it's very high-cost because it may hold the answer to the question of why anything exists in our universe at all each particle in our universe has its exact counterpart an antiparticle identical in every way but with the opposite charge and spin an electron has a positron of proton has an anti proton and so on and when a particle encounters its antiparticle partner when matter encounters antimatter the two can pair annihilate cancelling each other out completely and leaving only two photons to carry away their energy and it works in Reverse two particle and antiparticle pairs can be created from pure radiation in fact that's how we think the first particles were created in the very early universe but if matter and antimatter are always created in pairs then in the beginning of time there should have been exactly the same amount of both so where is all of the antimatter the better question is why is there any matter at all shouldn't everything just have annihilated again leaving only a vacuum bathed in light the most likely answer seems to be that the universe started out with a little more matter compared to antimatter if there were slightly more particles than anti particles then almost everything would have annihilated leaving universe full of photons and only very few particles that couldn't find an annihilation partner these days there are around a billion times more photons than there are particles of matter so we estimate that for every billion particles of matter that are naya lated only one survived and there's the mystery why were particles created with that one in a billion overabundance compared to anti particles it seems there must be something inherently different in the way the universe interacts with particles versus anti particles the universe must not treat the two symmetrically indeed many physicists think that the answer lies in the fundamental symmetries of the universe or rather in the breaking of these symmetries we've discussed this before there are three symmetries of the universe that physicists once believed were fundamental you should be able to perform any of these transformations or all of them and the laws of physics should be unchanged we have charge conjugation where positive and negative charges are swapped we have parity inversion where the universe is reflected through a mirror and time reversal where all particles have their direction of motion and spins exactly reversed if you apply all three of these transformations to a particle if you apply a cpt transformation then it becomes its own antiparticle because we expect the universe to be cpt symmetric we expect it to treat antimatter in exactly the same way as regular matter but one by one these presumed symmetries failed the first of all was parity with Chung Chung was famous cobalt-60 experiment proving that a mirror image of our universe would be distinguishable from our own then charge and parity combined or CP also fill with the observation of the peculiarity in the decay of K in isn't that CP violation may have contributed to the asymmetry of matter and antimatter in the early universe in a process called electro weak baryogenesis but at least at the level of CP violation that we've observed this isn't enough to explain the level of baryon asymmetry that does exist but remember that antimatter is what you get when you do a full cpt transformation of matter so maybe the violation of full charge parity and time symmetry is needed to explain this imbalance we saw in our previous episode that so far cbt symmetry looks safe and that's because we know that both CP and tea symmetries are separately broken and the breaking of tea symmetry could actually counteract CP violation preserving CP T symmetry in principle at least if CP T symmetry really is violated however it may explain why we live in a universe of matter and would undo a lot of what we think we know about quantum mechanics so good news bad news I guess the cpt theorem says that assuming our knowledge of special relativity and the standard model are correct then CP T symmetry must hold but we already know that our current understanding of the universe is incomplete it doesn't explain dark energy dark matter or this barrier and asymmetry problem so if there exists some underlying more fundamental theory maybe string theory for example then CP T symmetry may no longer be a foregone conclusion but how do we test for CP t violation the CP t theorem demands that an antiparticle must have the exact same properties as its matter counterpart besides the charge and spin thing it must have the same mass the same quantum energy levels and the same interactions with its environment so we need to make some antimatter and test it that's not exactly a simple process well actually making anti particles is straightforward enough for example positrons are antielectrons are created all the time in nature for example in the Sun or in radioactive decay or when cosmic rays hit the atmosphere which is how antimatter was discovered in the first place and more exotic antimatter like anti protons can be created in particle accelerators just by smashing regular matter together the problem is antimatter immediately annihilates with any matter it encounters so it's hard to keep the stuff around for long and that's particularly true of antimatter atoms which are electrically neutral and so are hard to even store using electric and magnetic fields to give you an idea of the effort involved take the simplest type of antimatter atom anti hydrogen consists of just a single antiproton plus a positron instead of the proton plus electron of regular hydrogen in 1999 NASA estimated that when taking all expenses into account just one gram of anti hydrogen cost sixty two point five trillion dollars you thought that gas was expensive so we're gonna have to wait a while before powering starships with antimatter engines fortunately you don't need anything like a whole gram of the stuff to do CPT experiments a handful of atoms is enough and so the cost of doing these experiments is many orders of magnitude lower one of the few facilities in the world capable of making anti hydrogen is at CERN in Switzerland they're the Alpha experiment is testing the behavior of anti hydrogen in multiple ways to see if it deviates from regular hydrogen deviations that could point to the violation of CPT symmetry alpha users CERN's proton synchrotron to get their anti protons the synchrotron accelerates protons to tens to hundreds of Giga electron volts of kinetic energy corresponding to over 99% of the speed of light these high-energy protons then hit a metal target and produce a zoo of particles and antiparticles some of these byproducts are antiprotons voltages applied to electrodes around the outside of the chamber direct the anti protons to a storage ring called the antiproton decelerator where they are slowed down by pulses of radio frequency electric fields as they travel around the ring they can then be redirected to a number of different experiments including alpha there the negatively charged anti protons are trapped by a combination of electric and magnetic fields in a so-called penning trap positrons also fly into this trap from a radioactive sodium 22 source and pair up with the anti protons creating anti hydrogen in previous experiments the now neutral anti hydrogen was no longer confined by the penning trap and so it drifted to the walls of the trap where it annihilated with the matter encountered although antihydrogen is electrically neutral it does have a small magnetic moment like a tiny bar magnet alpha introduces a new magnetic field that forces the antimatter to the center of the chamber in this way they've managed to keep anti hydrogen in the trap for several days the longer they can keep an anti atom around the more tests they can conduct on it and so the more precise their measurements will be with the anti hydrogen securely in the trap scientists measure the difference in energies between various positron orbitals in the anti atoms using laser spectroscopy the exact energy of one of these states is determined by many different factors the precise mass and charge of the particles their orbital angular momentum their magnetic and electric dipole moments and even the strength of the coupling between the particles and the quantum fluctuations of the vacuum any differences in these properties in antimatter versus matter will cause a shift in the laser frequency necessary to stimulate a transition in the atoms scientists measure this frequency then compare to the corresponding frequency in regular hydrogen the best measured transition in hydrogen is known with 15 digits of precision so even a tiny variation between hydrogen and anti hydrogen might be detected in a recent measurement alpha has been able to test cpt invariants down to 16 parts per billion so far no evidence of CPT violation but they've already made plans to push boundaries even further testing CPT with higher sensitivity another antiproton decelerator elena will come online next year and be able to deliver much slower anti protons which will mean way more anti hydrogen in a trap they expect this to dramatically improve their measurement precision alpha scientists are also building a new experiment similar to the original alpha a parada but rotated by 90 degrees alpha G will allow its anti-atoms to be dropped from the trap and freefall for some time the cpt theorem states the the acceleration of an anti atom in Earth's gravitational field should be exactly the same as for an atom but scientists want to test this they've even designed the contraption to allow room for the anti atoms to move up in the extremely unlikely but not completely Roy out off chance that anti-atoms experienced anti-gravity such a discovery would be a huge surprise and will cause all sorts of terrible consequences to our current model of the universe so scientists aren't holding their breath they're pretty sure antimatter interacts with gravity in the exact same way as matter but why not test it okay so apparently we have another one of these space-time episodes where scientists busted ass to break physics and didn't but as I've said before that's cool and amazing in itself we now understand the symmetries of nature too much credit precision which means we have a better idea of where to look for this strange broken symmetry that leads to matter antimatter imbalances and to the fact that we have matter in the universe at all maybe it'll come from CPT violations miserable only in future experiments or maybe it won't instead proving beyond a doubt that CPT truly is an underlying symmetry of space-time we like to give shoutouts to our patreon supporters but today we have a special request who forego the direct shout out what's assumed our extreme gratitude is implied and instead to wish a very very happy birthday to Christie Michael John Christie we tried to bake you a cake made out of antimatter guaranteed to aid you - one year per slice unfortunately it also annihilates you unless you're also made of antimatter but Christie you can't be made of antimatter because obviously you matter very very much - someone will keep working on the cake but in the meantime have a wonderful orbital revolution from me and all of the space-time crew [Music] [Music] [Music] you

Channel: PBS Space Time

Views: 457,464

Rating: 4.9424663 out of 5

Keywords: Space, Outer Space, Physics, Astrophysics, Quantum Mechanics, Space Physics, PBS, Space Time, Time, PBS Space Time, Matt O’Dowd, Astrobiology, Einstein, Einsteinian Physics, General Relativity, Special Relativity, Dark Energy, Dark Matter, Black Holes, The Universe, Math, Science Fiction, Calculus, Maths, Holographic Universe, Holographic Principle, Rare Earth, Anthropic Principle, Weak Anthropic Principle, Strong Anthropic Principle

Id: JOMrbkZqTcs

Length: 13min 47sec (827 seconds)

Published: Wed Jul 08 2020

Reddit Comments

[u/Drgn_nut]

No.

Snark aside, the experiments he talked about are pretty amazing. I do wish that theoretical physicists would spend more time trying to explain experiments that already deviate from existing models, but the cool thing about experimental physics is that the techniques used to get to the needed levels of precision usually bleed into industry in really interesting ways.

[u/mathplusU]

So if CPT symmetry is dead does that help explain the current gridlock in science? All of our models from the standard model to quantum mechanics are based on some kind of symmetry. If we don't have symmetry from the onset why are we relying on it deeper down?

Sabine Hossenfelder argues we are "Lost in Math". Maybe we're lost in symmetry instead.

We no longer have a "god of the gaps". We have a "god of the asymmetric".