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In the series Crisis of Infinite Earths, the whole story is that there is a wave of antimatter rampaging through the multiverse. So I got interested and googled "how to create antimatter", and I found out that when an antiproton and a positron are present in an atom, it creates an anti-hydrogen atom. My question is, what is anti-hydrogen? What can be its properties? We all know that hydrogen is flammable, so is anti-hydrogen a non-flammable material? Because it has opposite properties, right?

Nihar Karve
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alexv0rden
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In particle physics, every type of particle is associated with an antiparticle with the same mass but with opposite physical charges (such as electric charge)

Bold mine. Note physical charges. There are specific numbers associated with elementary particles that define them, and those are the ones reversed, as in the proton antiproton case, or the electron positron case.

A world made completely out of antimatter would have the same chemical and electric etc interactions.

We all know that hydrogen is flammable, so is anti-hydrogen a non-flammable material? Because it has opposite properties, right?

The "opposite" does not go to interactions, only to quantum numbers. So yes antihydrogen it would be flammable in an antimatter world. There is an ongoing search to see whether antimatter exists in bulk in our universe .

anna v
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    More simply, "non-flammability" is inversion at the "semantic level", not the "physical level". It is about human cognition (the place where 'magic' works). A dog made of antimatter does not become a non-dog. – David Tonhofer Jun 06 '21 at 12:31
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    @DavidTonhofer however it would become a non-dog if it ever came into contact with a dog (or anything) made of matter. – alessandro Jun 06 '21 at 17:40
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    Anti-hydrogen is flammable when anti-oxygen is present to react with it. If oxygen, rather than anti-oxygen, is present, the result would be a lot more than flame. – Andreas Blass Jun 06 '21 at 20:44
  • I notice you don't (expilcitly) mention gravitational, weak force, and strong force interactions. – Eric Towers Jun 06 '21 at 21:32
  • @EricTowers Involving the weak force complicates things in ways not useful to OP, and the gravitational properties of antimatter are not on firm experimental grounds yet. – eyeballfrog Jun 06 '21 at 23:28
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    @DavidTonhofer A dog made of anti-matter is not a non-dog, it's an anti-dog... – Oscar Bravo Jun 07 '21 at 12:56
  • @alessandro: "it would become a non-dog if it ever came into contact with a dog (or anything) made of matter" As would everything else within a fairly impressive radius... – ShadowRanger Jun 07 '21 at 15:06
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    An anti-dog would be vegetarian, rather than a meat eater. It would have an exoskeleton rather than an endoskeleton. It would have to be either aquatic, or avian (not sure which of those two is the opposite of terrestrial) It would be sessile, rather than motile, single-celled, rather than multi-celled, would stand up when told to "sit," its puppies would be hideous rather than cute, and it would be Woman's worst nightmare rather than being Man's best friend. – Solomon Slow Jun 07 '21 at 15:38
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The properties of anti-matter in general are very similar to properties of matter. Richard Feynman considered the problem of if we made radio contact with an alien civilization, how would we be able to tell if they were made of matter or anti-matter? It turns out to be a complicated process. See 52-8.

Anti-hydrogen is very much like hydrogen. It would combine with anti-oxygen to make anti-water (I am making up names, but it should be clear what I mean.) Anti-water could support life just like water. Anti-people would be made of familiar anti-elements, which would have the same chemistry as elements.

The only difference between anti-hydrogen and hydrogen is that it is made of an anti-electron (or positron) and an anti-proton. The only difference between an anti-electronand an electron is the anti-electron has a positive charge instead of negative. Likewise an anti-proton has a negative change instead of positive.

Anti-electrons repel each other just like electrons do. Anti-electrons are attracted to anti-protons, just like electrons and protons attract.

Anti-electrons in anti-atoms would interact with each other in the same kind of way as electrons in atoms do, and would form the same kinds of chemical bonds.

As long as anti-matter and matter don't come in contact, they pretty much have identical behavior. Of course, if they do come in contact, they annihilate each other in a flash of gamma rays.

mmesser314
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    As well as the Feynman article, also see the Wu experiment. "Chien-Shiung Wu's role in the discovery was mentioned in the Nobel prize acceptance speech, but was not honored until 1978, when she was awarded the first Wolf Prize". – PM 2Ring Jun 06 '21 at 05:13
  • In an antimatter world. All the electrical engineers wouldn't have to use "Conventional Current" because charges in their metal wires really would flow from positive to negative. –  Jun 07 '21 at 04:03
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    There is also the ongoing ALPHA experiment at CERN, e.g. studying the gravitational properties of antimatter. – Peter Mortensen Jun 07 '21 at 09:54
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    @user4574 Well, except that their anti-Ben Franklin would still have called the charge that built up on the anti-glass when it was rubbed with anti-fabric "positive", and so their notions of positive and negative would be opposite ours, so they'd still have "conventional" current that's the opposite of "anti-electron" current. – HiddenWindshield Jun 07 '21 at 16:23
  • Do we know what "come into contact" means in practice? If you put a wafer of anti-SiO2 onto a wafer of SiO2 would that be "in contact"? – Spehro Pefhany Jun 07 '21 at 17:59
  • @SpehroPefhany - If an anti-atom (containing anti-electrons) came into contact with an atom (containing electrons), the electrons and anti-electrons would annihilate within a microsecond or so. – mmesser314 Jun 07 '21 at 19:39
  • @mmesser314 But what constitutes "contact"? The wave functions are kind of fuzzy AFAIUI, they're not particles being fired at each other in an accelerator. Maybe the electron and positron clouds would be mutually attracted and make contact? – Spehro Pefhany Jun 07 '21 at 19:42
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    Matter screen SPF 50... https://dilbert.com/strip/2008-07-01 –  Jun 07 '21 at 20:10
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    @SpehroPefhany - Electrons and positrons do attract, but they don't instantly annihilate. A free electron and free positron can form a bound state something like a hydrogen atom. It is called positronium. I mis-remembered the lifetime. It lasts about a tenth of a nanosecond before annihilating itself, which is still a reasonably long time by subatomic timescale standards. – mmesser314 Jun 07 '21 at 22:22
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    @SpehroPefhany I don't know about quartz & antimatter quartz wafers, but I give some details about the speed of interaction of hydrogen & antihydrogen at interstellar densities in this answer: https://physics.stackexchange.com/a/590085/123208 – PM 2Ring Jun 08 '21 at 10:03