# What’s the matter with antimatter?

Recently we travelled to The Dark Side to learn about mysterious dark matter and dark energy, today we turn to another curious substance in our universe – antimatter. Antimatter’s father is widely regarded as Paul Dirac, who in 1928 predicted the possibility of anti-electrons. Dirac was working on an equation that would combine quantum theory and special relativity – a theory to describe the behaviour of an electron (a quantum particle) moving at a speed close to the speed of light. This equation was the relativistic version of Schrodinger’s wave equation and it had two solutions. Just as the square root of a number can have two solutions, a positive and a negative (square root of 9 is 3 and -3), the solution to Dirac’s equation has one for an electron with positive charge and one for an electron with negative charge. From the theory Dirac then made a bold move and postulated that for every particle there is exists a corresponding antiparticle with an opposite charge to its partner. The existence of Dirac’s antiparticles would indeed be verified at particle accelerators in years to come.

Particles have various quantum numbers that characterise their nature. The three that shall concern us today will be charge, baryon number and lepton number. Time for some terminology and book-keeping. Baryons are quark-based particles and are susceptible to the strong force, protons and neutrons are therefore baryons because they are made of three quarks. Baryons, funnily enough, have a baryon number of +1. Other particles which are not susceptible to the strong force and are not quark based are known as leptons, things like electrons and neutrons. These leptons have a lepton number of +1. Bit silly doesn’t it seem giving baryons and leptons a corresponding number of +1, what else would they have? Well that’s the whole point of the anti-particles, they have the number with an opposite sign! So an anti-proton has a baryon number of -1, an anti-neutron has a baryon number of -1 and an anti-electron, properly known as a positron, has a lepton number of -1. Finally any lepton has a baryon number of 0 and visa versa. Then of course, last but not least, we have charge. If a proton has a positive charge of +1 the anti-proton has a negative charge of -1. All of this was theorised and the experimental results at particle accelerator sites went on to confirm the existence of such entities matching the descriptions.

Collisions between particles and antiparticles lead to annihilations and give off energy (in the form of photons) proportional to the total mass of the particles in accordance with Einstein’s equation E=mc^2. Antiparticles are also created in regions of the universe where high-energy particle collisions take place, such as high-energy cosmic rays colliding with the Earth’s atmosphere. This antimatter can then be detected in the traces of its products after it has annihilated with matter – for example gamma rays which are themselves photons of the highest observed range of photon energy.

Now looking around us at everyday objects, the Earth, planets in the solar system, stars… why is it that matter seems to vastly outweigh antimatter? Since, all known processes for creating massive particles create both in equal quantities.  The asymmetry of matter and antimatter in the universe is another great mystery but we should be very thankful for it. If an equal amount had existed shortly after the Big Bang all matter would have annihilated with its antimatter counterparts leaving nothing but energy behind. In fact it is estimated that in the early universe there was only one extra matter particle for every billion-matter antimatter pairs! Whatever hypothetical process that took place in the early universe that caused the matter-antimatter asymmetry is termed, by cosmologists, Baryogenesis (confusingly not solely to do with baryons). The difference in the abundance of matter and antimatter in the early universe left behind the matter remnants we see today, which allowed the formation of the universe as we know it… thank you Baryogenesis.

Anti-matter is a classic go-to weapon of science fiction stories due to its annihilating power and high energy potential. Recent examples include Angels & Demons where Professor Langdon tries to save Vatican City from an antimatter bomb and Star Trek’s starship the Enterprise which uses the energy released from matter-antimatter annihilation as propulsion to achieve faster-than-light travel. Though the substance anti-matter exists in the real world the feasibility of harnessing its powers is best left to the realm of sci-fi. Think about, in order to harness its power and manipulate it as a weapon, we would have to, as a first step, be able to store it. By what means could we achieve this?! Any container we put it in, it would annihilate with the matter that constitutes the walls of the container itself! Antimatter is a tricksy beast, storing it would be like trying to grasp a fistful of air.

Fun facts to round off, antimatter is the most expensive stuff on the planet, weighing in at a whopping \$62.5 trillion a gram! However as obvious from the storage problem, a gram has not been produced. The most that has been created and stored at a time is about a billion antiprotons, but that’s only a meek one millionth of a billionth of a gram. If you fancy getting up close with some antimatter however, the answer is most likely sitting in your kitchen. Go grab a banana! Bananas contain potassium-40 which as it decays, gives off a positron (an “anti-electron”) at a rate of about one every 75 minutes. Too bad it collides with the nearest electron pretty much instantly…

## 26 responses to “What’s the matter with antimatter?”

1. Gravity is a force relating to mass, which is derived from matter. Acceleration increases the force of gravity. Does the existence of antimatter indicate there may be antigravity? Have we tried accelerating antimatter to measure its anti-gravity?

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• Unfortunately antimatter and matter have the same mass; they are not opposites so they have the same gravitational effects (not that these are understood in full on a quantum level). Anti-gravity remains science fiction for now!

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2. I first encountered anti-matter back in the early days of Astounding stories where it was called contra-terrene. At least one story there envisioned an object of matter and CT (contra-terrene ) joined with a screw thread wherein they were both magnetized with the same polarity so that magnetic repulsion kept them from touching. There is some information at http://articles.adsabs.harvard.edu//full/1940ApJ….91..257R/0000258.000.html

Just recently an anti hydrogen molecule was created and tested. See https://home.cern/about/updates/2014/01/antimatter-experiment-produces-first-beam-antihydrogen see also https://www.sciencedaily.com/releases/2016/01/160126110805.htm

Considering the power of bananas I imagine a star ship well equipped with bananas might interest NASA.

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3. So interesting!!
So the collision between a positron and electron from potassium in bananas, is that damaging to skin cells?

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• No do not fear, only one positron every 75 minutes or so is emitted. The energy given off in the form of radiation is absolutely minuscule! Thank you for reading!

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4. That’s bananas! This makes me think of the regeneration process like leaves that fall to the grouns.

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5. One thought came to me insofar as antiparticles is concerned. According to quantum theory there is a constant random generation of particles and antiparticles throughout all space and normally they obliterate each other quickly but according to Hawking when this generation takes place near a black hole one of the particles is swallowed by the hole leaving the other to exist. Is this a significant source of antimatter particles?

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• I didn’t know about the prejudice of black holes for swallowing only antimatter particles and this is the first indication I have heard that might have some bearing as to why more matter than antimatter exists. Could there be some primal condition where a huge black hole effect took place when the universe was new?

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• Antiparticles do not have negative energy. Although it is true that the particle that crosses the horizon has negative energy, it is not essential that only the antiparticle will fall beyond the horizon. The rest mass of antiparticles is positive (or zero), just like the mass of ordinary particles. That is, the mass of a positron is the same positive value as the mass of an electron, for instance.

Hawking conjectured that the particle that falls in the horizon will somehow acquire negative energy, which reduces the overall mass energy of the black hole. Basically, the negative energy conjecture is a mathematical trick, that we often use in QFT (read Casimir effect), and such particles have only mathematical existence (virtual particles). In this trick however, the negative energy particle reduces the energy of the black hole, while the positive energy counterpart accounts for the radiated energy

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• I’ve decided to swot up on the topic and my next post will be about Hawking radiation as it combines Black Holes and Antimatter – hopefully i’ll be able to give more clarity then!

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• There is an article at https://www.sciencedaily.com/releases/2017/01/170105143458.htm which indicates a plenitude of black holes in the very early universe which may have some relevance to the speculation that black hole preference to gobbling only antimatter has led to a universe where only matter is common. One thought in vague relation to that is that no white holes seem to have been spotted which would be the nether end of a black hole into a different universe. Perhaps the original Big Bang was a white hole that sucked up or somehow destroyed a major portion of the antimatter particles granting us the universe we have now,

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6. I love it and I’m so sad that I never choose this branch of science to study, but I read books about quantum theory. I read about mater and anti-mater in the books of Stephen Hawking, Lawrence Krauss and other scientist, but I find this discovery logic and absurd. For us as humans everything have its own opposite, in any kind and level of life, in our psychological life we have two opposite our desire and reason, ego and intuition, and we see that in our sociological life. Even in mathematics the +1 is the opposite to -1. We find in logic 0 and 1, true and false. Our task and our first aim is to find and the scientist work for and say all the time, THE THEORY THAT EXPLAIN EVERYTHING. From the ancient ages to our now we don’t know much better than the precedent generations about our universe, the mysteries of the universe still infinite and well hidden behind an invisible mathematical universe that we have a great desire to understand it. Good luck for humanity in its task.

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7. The problem I see is that matter, anti matter, and dark matter (perhaps even anti dark matter) dont seem to conform to a simple elegant mathematical structure. The universe chooses the most simplest form, the most energetically stable form, yet the math we have is convoluted and complicated (not complex, simply complicated)
The reason I even mentioned anti dark matter is an idea I had, as a start. The octonian group has some very interesting properties that I have seen mirrored in physics, where generators reaching the starting point simultaneously are akin to the annihilations we see among these stages of matter/energy existence.
Ultimately I did come to the conclusion that the octonian group is a great first step in mapping out things from the physics perspective, it wasn’t complete.
Maybe one day I will sit down with somebody that has access to a lab and prove my theory. Or maybe it might be another 500 years lol. The breakthrough was the “shape” of space-time. With that, so many things just snap into place so beautifully.

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8. Dirac’s remarkable mathematical prediction reminds me of the story of the Higgs. It seems the universe as we know it is mathematical.
Without matter we would have no periodic table and no carbon based life. Why is it that as atoms get larger they become more unstable and even radio active? Some scientists have predicted that much bigger atoms are indeed stable and they speak of islands of stability..
Your banana made me smile , to often we think of radio activity as abnormal because of its recent discovery but it is part of the very fabric of our world and all living things. Thank you for uncovering another mystery might I suggest that at sometime an introduction to radioactivity would be much appreciated.

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• This decay of matter put me into a Wiki article on the decay of the proton at https://en.wikipedia.org/wiki/Proton_decay . Evidently the decay is still theoretical as it has never been observed and there are several theories in the matter. There are a lot of Feynman diagrams in the article which I do not understand. But evidently many particles are fragile. A free neutron has a life of about ten minutes although it is stable within an atom. The article indicates a decaying proton becomes a positron and a pion which strikes me as peculiar since a positron has the mass of an electron which is over a thousand times less than a proton and a pion made of two quarks is also very light. Perhaps the lost mass goes into energy emission.

Anyway I assume, since the universe was created out of nothing, matter and its opposite antimatter might be considered positive and negative nothing which sums as nothing plus the energy emitted. It’s probably cockeyed logic but only a wild guess.

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• To be honest this article makes no real sense to me and I assume it is beyond the understanding of the layman. It seems the field of physics is so vast that each dedicated group of researchers are studying their own particular area of research.

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• Thank you Kertsen. Yes maths appears to be, more and more, the language the universe is written in. The nature of mathematics is something that has always troubled me, essentially a construct invented from the minds of man yet so accurately reflects the nature and workings on the independent world. Food for thought for me. I am adding radioactivity to my list of upcoming posts – thank you for the suggestion!

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• An interesting observation but then language itself has arisen from the human mind and we are still not sure of its origin. Spoken language came long before written language and it was the first capability to link enquiring minds.

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9. So if I ask ‘What’s the anti-matter?’ do I mean ‘What’s going right?’
Oh dear, so much for a purely linguistic approach …

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• Haha yes I guess so. Linguists is definitely not my strong suit!

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10. ……As you mentioned, the attempt to contain / grasp anti-matter is a costly and perilous pursuit to self destruction (non-existence)…..and any factual / tested theory of its proof of existence is also questionable as it is also challenged by the shrodinger cat & the double slit experiment….as quantum particles behave relevant to observation of the observer….despite all scientific advancements, even the big bang theory has come to a halt for a plausible explanation of what happened before the big bang where time T=0, where all concepts /constructs as we know it collapses……un-imaginable …..that’s the word…..you cant see the picture when you are in the frame can you ??…further confounded by the multiverse theory and the theory of many possible outcomes existing at the same time….below two links seem to explain our predicament / pardox with the physical world…..

And the below link seems to support Nikola tesla’s attempt to go beyond the meta-physical world to make greater advance in sciences as we know it. It also supports description of Mikail Kaku’s / Einestines God of order / synchrony / harmony…….by the definition of the paradox…….the explanation of and picturisation of the known unknown……

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