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Sci-Fi Space

Antimatter and Antistars? 156

Posted by Cliff from the a-what-if-excercise-for-the-astrophysicists-out-there dept.
payndz asks: "I'm currently writing an SF novel, and came up with a weird thought for a piece of background flavour that, if there's any scientific basis for it, might get expanded into a larger element. The most up-to-date theories for the creation of the universe 13.7 billion years ago (give or take...) suggest that at the Big Bang, matter *and* antimatter were created. Over time, the fact that there was slightly more matter than antimatter means that mutual annihilation has left a universe of matter. (I'm not going to open up the whole can of 'dark matter' worms, unless somebody wants to...). I have a 'what if' question, which since Hubert Farnsworth isn't around I thought would get some good responses here: what if, rather than antimatter being annihilated by matter in the universe at large, there are 'clumps' of both matter and antimatter making up the universe? Since our clump is almost entirely matter, billions of LY away could there be galaxies made up of antimatter?More to the point, what physical properties would these galaxies have? Would a star made of antimatter function in the same way as a matter star, and would its emissions be made of antiparticles? Can you have anti-photons, and if you could, what impact would they have on any matter they illuminated? Could life evolve in an antimatter environment?"
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Antimatter and Antistars? More

Antimatter and Antistars?

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  • silly constraints (Score:1, Interesting)

    by chewy ( 38468 )
    Since you are writing fiction, it doesn't really matter whether it's real at all or not. All real physics are only just theory, so anything you can dream of should be possible in your fantasies!

    • Re:silly constraints (Score:4, Insightful)

      by Lshmael ( 603746 ) on Friday July 25, 2003 @04:05AM (#6530086) Homepage
      But he isn't writing a fantasy, he is writing science fiction. Therefore, his "constraints" are valid, since they are what define the genre. For example, writing about a flat earth should not be considered true science fiction, for the simple reason that it is quite unlikely that the earth is flat. Standard scientific opinion is that the earth is round. While it is true that much of astrophysics is "theory," it is educated theory.
      • "
        writing about a flat earth should not be considered true science fiction"


        Fortunately I don't see Terry Pratchett as SF either :)

        But there are scifi (Bladerunner, some Iain Banks books, Neuromancer. Matrix) which directly contradicts true "facts" or known science, yet are still called scifi. My point is rather that one shouldn't try to make something fit inside some "genre". Write what fascinates and compells you.
        • What are the true facts of known science that are directly contradicted in Bladerunner? Same with Neuromancer. Suggesting things that are beyond "known science" is not, necessarily, a contradiction.
        • "writing about a flat earth should not be considered true science fiction"

          Fortunately I don't see Terry Pratchett as SF either :)

          I recommend Terry Pratchett's Strata, which is science fiction and deals rather scientifically with a flat Earth.

      • Re:silly constraints (Score:5, Insightful)

        by sql*kitten ( 1359 ) * on Friday July 25, 2003 @07:27AM (#6530538)
        But he isn't writing a fantasy, he is writing science fiction. Therefore, his "constraints" are valid, since they are what define the genre.

        Actually, the thing that matters in scifi is consistency. You can make up the rules, but once you have you have to stick to them, otherwise your stories disintegrate into deus ex machina handwaving. That is why Star Trek is bad scifi* - the capabilities of all its technological artifacts change from episode to episode, and they can always "technobabble" their way out of any situation. In Star Trek, technology is indistinguishable from magic. Far, far better is the work of Alastair Reynolds - he does use technologies which don't yet exist, but his characters are forced to work within fixed limitations (i.e. humans colonize the nearby stars relying on relativistic time dilation and suspended animation - there is no FTL, and anyone who tries it fails, no matter how useful it might be for the story).

        --
        * However it can be good drama, it's not scifi even tho' it's in space.
        • That is why Star Trek is bad scifi* - the capabilities of all its technological artifacts change from episode to episode, and they can always "technobabble" their way out of any situation.

          I don't think Star Trek was ever intended to be great Sci Fi. The original series pushed the then-modern social envelope more than anything. It really wasn't until the 1990's that it decomposed into a politically-correct serial.
        • Comment removed based on user account deletion
    • Since you are writing fiction, it doesn't really matter whether it's real at all or not. All real physics are only just theory, so anything you can dream of should be possible in your fantasies!

      You're Dubya's speech writer, aren't you???

  • Don't land on one :-) (Score:5, Informative)

    by oren ( 78897 ) on Friday July 25, 2003 @03:48AM (#6530042)
    Larry Niven had this great short story where Elephant looks for the most unusual piece of real estate in the known space... nicknamed "Cannonball", it is a solar system zooming *very fast* through our galaxy. While that is unusual by itself, it isn't the *most* unusual thing about it, as you can guess.

    Luckily for him his pilot is a coward, so they don't land :-)

    Seriously, the existrance of large amount of anti matter (whole galaxies of it) isn't _that_ far fetched. Consider that the original big-bang universe is made out of hot plasma. A blob of matter pressed against a blob of anti matter will create a terribly violent reaction in the interface zone; this would act as a "wall" repelling both matter and anti-matter away from it, preserving them as seperate regions. Also, any electrical current flowing through the plasma will tend to separate matter and anti-matter. Given the whole universe is expanding madly in the duration it is possible that ant-matter "islands" survived.

    AFAIK (IANAP) anti-matter galaxies/stars would be indistinguishible from normal-matter ones. Photons don;t care whether they are created by matter fusion or anti-matter fusion, etc.

  • Don't go there (Score:3, Funny)

    by the_DaRKaNGLe ( 652382 ) on Friday July 25, 2003 @03:49AM (#6530047) Homepage
    It has been done before, about a million times in one form or another. Somhow this article triggered some Startrek flashback...

  • Larry Niven thinks so... (Score:4, Interesting)

    by Thornae ( 53316 ) on Friday July 25, 2003 @03:49AM (#6530049)
    There's a Larry Niven short story called Flatlander which deals with the concept of antimatter stellar objects - only briefly, but it's worth a read.
    Also, wander up to your nearest university and look up the astro-physics department. Chances are there'll be a couple of knowledgable types in there who could point you in the right direction.

  • Physical properties of antimatter galaxies (Score:5, Funny)

    by baywulf ( 214371 ) on Friday July 25, 2003 @03:51AM (#6530052)
    "Since our clump is almost entirely matter, billions of LY away could there be galaxies made up of antimatter?More to the point, what physical properties would these galaxies have?"

    One thing is for sure. There would be a person identical to you except they would have a goatee and no sleeves on their uniform.

  • Some info as i remember (Score:5, Informative)

    by Sklivvz ( 167003 ) * <`marco.cecconi' `at' `gmail.com'> on Friday July 25, 2003 @03:54AM (#6530061) Homepage Journal
    First of all, there's basically no difference between a galaxy (or a physical body) made of matter and antimatter... Actually you wouldn't be able to tell. The major physical difference is the charge of particles (e.g. anti-electrons, or positrons, have +ve charge) but of course you wouldn't be able to tell since you would call +ve charge -ve and vice versa.

    Secondly, according to the theories you mentioned, there's basically very little chance that large lumps of antimatter were formed during the big bang, since most of the annihilation would have taken place at a stage when all the matter was condended in a very small place, and therefore the distribution of antimatter would be quite uniform (so you wouldn't have a galaxy of am here and one of normal matter there).

    Thirdly, there are no antiphotons. Photons are the antiparticles of themselves!

    Hope it helps!
    • I'm sorry .. this is so lame .. but your sig is just fantastic.

      Oh ghod, what have I become .. a sig fanboy ..

      M

    • Re:Some info as i remember (Score:5, Insightful)

      by cthugha ( 185672 ) on Friday July 25, 2003 @04:45AM (#6530174)

      Not only that, but it would seem that any clump of A-M of less than galactic size would have a hard time existing in a harsh, matter-filled region. A-M objects in an M galaxy would have to contend with the fact that interstellar space isn't empty, but has a faint hydrogen "wind" blowing thorugh it. For an inert body like an asteroid or rogue planet, this would mean gradual but inevitable erosion. For a star system, things might get interesting, since the star's own solar wind would sweep the interstellar medium out to its heliopause, which would presumably show up as a gamma-ray "halo" surrounding the system.

      I wouldn't even want to speculate on the conditions necessary for the formation of such a system, since I'm simply talking out of my rear-end here (I Am Not An Astrophysicist).

      • Re:Some info as i remember (Score:2, Interesting)

        by Gyl ( 318790 )
        This could be an interesting effect for a sci-fi. Assume the universe is large enough to hold pockets of matter and anti-matter, then the regions between these pockets may be highly active areas of near empty space where matter and anti-matter collide and release lots of energy. Like a sort of second cosmic microwave background, though it probably wouldn't be microwaves.


        Could be fun designing a starship to cross this boudry.

        • Congratulations, you've crossed the matter/antimatter boundary with a starship. Now what do you do?

          I mean, you're sure as heck not going to land anywhere.

          • Re:Some info as i remember (Score:1, Funny)

            by Anonymous Coward

            Congratulations, you've crossed the matter/antimatter boundary with a starship. Now what do you do?

            I'm going to Anti-Disney World!!

          • well, that's for the story writer to decide.


            You know how scientists have lots of trouble producing even tiny amounts of anti-matter. Where better to get copious amounts of the stuff? Could be used for such things as alternative energy source, or removing planets to make way for hyperspace bypasses.

      • That'd be kind of interesting, could look something like a kind of large "planetary" nebula.
      • One condition for the possible existance of an anti-matter galaxy in a region of matter galaxies: some crackpot alien race built the thing.

        I have no idea why they might want to, and very little conception of where they'd get the energy to do it, but these silly thoughts occur to me sometimes.
    • "First of all, there's basically no difference between a galaxy (or a physical body) made of matter and antimatter... Actually you wouldn't be able to tell." You may be familiar with the "right hand rule" which defines the direction of many physical interactions that are mathematically described by a cross-product. Antiparticles should behave oppositely, following an anti-right hand rule. A favorite quote from my professor at Drake. "If you go to shake hands with an alien and he reaches out with his lef
    • > since most of the annihilation would have taken place at a stage when all the matter was condended

      ah, but annihilation releases energy, and the energy would
      also have been extremely condensed, leading to the
      formation of new matter, in equal proportions of charge.
      this is during the period of rapid inflation, at the end of
      which, i speculate, equilibrium between matter creation
      and destruction existed. by that time, clumping had
      already occurred, corresponding to galatic superclusters.

      hey, it's plausible.

  • Shameless Plagiarism (Score:5, Insightful)

    by benjamindees ( 441808 ) on Friday July 25, 2003 @04:27AM (#6530137) Homepage
    (picks up "Six Not-So-Easy Pieces" by Richard Feynman next to computer)

    In this fundamental physics book, Feynman describes all of the states of physical matter and the laws of symmetry that go along with them. When discussing the right and left-handed rules, he asks the obvious question of whether they are arbitrarily chosen; whether right-handed means anything other than in opposition to left-handed. He asks this to spur our interest in discovering the basis for the symmetry of physical laws.

    To illustrate, he imagines a conversation between a human and a distant alien, the purpose of which is for the human to communicate to the alien, after describing the human body and anything else of import, which hand is the left and which is the right, in order to know on which side to place the human heart. After dismissing a few possible physical phenomena by which this information could be conveyed, Feynman describes an instance (during a weak decay of a cobalt nucleus) in which the emitted electron always has a left angular momentum. This, he says, can be used to indicate to our alien friend which is left and which is right. Hold onto that for a second...

    In the next section, he describes antimatter. He first theorizes that, other than annhilating each other on contact, objects made entirely of antimatter would not be noticeably different from those made of matter: It is one of the principles of the symmetry of physics, the equations seem to show, that if a clock, say, were made of matter on one hand, and then we made the same clock of antimatter, it would run in this (exact same) way. He then adds the example of the left-handed beta decay above by constructing a theoretical antimatter clock made of cobalt nuclei. He speculates that since left and right-handed matter clocks could be constructed to behave differently, thus violating the law of mirror symmetry, that antimatter clocks would also behave dissimilarly depending upon their handedness.

    He goes through all of that to simply tell us that a left-handed matter clock is equivalent in every way to a right-handed antimatter clock. Unfortunately for sci-fi novelists, changing matter to antimatter merely alters the handedness of the particles, rather than actually violating symmetry or having any other noticeable effect. Of course, his lectures are no longer cutting-edge and the book only gives a laymans description of the underlying physics, but it doesn't look too good.

    Feynman ends up concluding:

    So, if our Martian is made of antimatter and we give him instructions to make this "right" handed model like us, it will, of course, come out the other way around. What would happen when [...] we each have taught the other to make space ships and we meet halfway in empty space? We have instructed each other on our traditions, and so forth, and the two of us come rushing out to shake hands. Well, if he puts out his left hand, watch out!

    • Exactly. If we lived in an "anti-matter" world, we would've have noticed, and would've just had different textbooks..

    • Re:Shameless Plagiarism (Score:1, Informative)

      by jiahao ( 73293 )
      Check out CPT violation on the net. Feynman is 40 years out of date on this topic.

    • actually... (Score:1, Informative)

      by Anonymous Coward
      What you quoted is the parity conservation. However, if you take charge into the consideration, there is a way to correctly tell a distant alien the concept of "left" and "right."

      CP (charge & parity) is violated.
    • He goes through all of that to simply tell us that a left-handed matter clock is equivalent in every way to a right-handed antimatter clock. Unfortunately for sci-fi novelists, changing matter to antimatter merely alters the handedness of the particles, rather than actually violating symmetry or having any other noticeable effect. Of course, his lectures are no longer cutting-edge and the book only gives a laymans description of the underlying physics, but it doesn't look too good.

      Hmmm. I was going to s

  • Heyyyy (Score:1, Funny)

    by Anonymous Coward
    I am fucked up and that was quite the idea for a book. I consider it quite entertaining.

  • photons (Score:2, Informative)

    by BoxedFlame ( 231097 )
    The equations that describe matter and anti-matter have identical solutions for the case of photons, meaning that anti-photons and photons are the exact same thing. This is logical since if they were not then what would photons and anti-photons react to create?
  • I recall reading somewhere that animatter is what matter would be but traveling the oposite direction in time. Hell, what do I know? I count boxes for a living.

  • WTF? Do your own research! And protect yourself! (Score:5, Insightful)

    by WIAKywbfatw ( 307557 ) on Friday July 25, 2003 @06:24AM (#6530410) Journal
    Seriously, some recent Ask Slashdot's have been ridiculous - doesn't anyone know how to use Google, etc anymore?

    This one takes the biscuit though. You're a writer (or want to be) - at the very least you should be able to do your own research for your work!

    Posting an Ask Slashdot is a very bad idea, for at least two reasons:

    1. There's no way you can easily distinguish between accurate and inaccurate statements.

    Just because something quotes a scientist or it's been modded up it doesn't make it any more reliable then anything else.

    2. You leave yourself open to litigation.

    George Lucas makes a point of not looking at Star Wars fan fiction because he doesn't want to leave himself vulnerable to the guy who'll scream "Hey, you stole that scene/character/whatever in Episode III from my story!". You might not have billions to lose but by canvassing for information and ideas so publicly you're still leaving yourself wide open to that sort of allegation.

    You might think that Slashdot is an open forum, populated by open source advocates who would all be opposed to intellectual property litigation and would do nothing more than help out and wish you luck but it'll only take one asshole to prove you wrong.

    Someone's bound to mod this down as flamebait or as a troll but if you're going to be an author then you can't afford to ignore this stuff.
    • Why doesn't anyone consider 'Ask Slashdot' to be reasearch?

      Seems like you're the only one around here crufty enough to think it isn't. Most people have been giving lucid, well-thought out responses. Then there's the "I don't like this question, so I'll bitch" troll. Come on, whine a little more about ask slashdot! You can do it!

      Wow are there a lot of whiney people on slashdot.
    • Point One is excellent; if you're serious about writing hard science fiction, please be sure to confirm any advice you receive here.

      As for Point Two ... unless 1) somebody posts detailed plot, story, or character information here, 2) you are dumb enough to include it in your book, and 3) your book is lucky enough to make it into print after you include unsolicited fan fiction in it, you should be fine. The SF writing community trades research all the time; you can see it in action over on the SFF.net [sff.net] or

    • George Lucas makes a point of not looking at Star Wars fan fiction because he doesn't want to leave himself vulnerable to the guy who'll scream "Hey, you stole that scene/character/whatever in Episode III from my story!".

      As much as I hate fan fiction, somehow I feel like that would make for a much better Episode III.
    • I think it's a fine idea for people to solicit ideas on slashdot. It is an open forum, and many of the popular posts express sympathy for the free expression of ideas.

      I wish more people would do so. I don't look forward to a society where everyone is afraid to ask questions in public for fear of being sued.

      • Substitute "program" for "book" and instead of helping him with him with science let's say we're helping him with his code. Now factor in that it's not an open-source project (I'm assuming he's not going to make his novel free as in speech.

        How many people on Slashdot do you think would help someone else code a closed-source (possibly non-free) application? How is it any different because it's a book? That's partially where I'm coming from but I'm trying to be pragmatic, hence I responded with caveats rathe
  • firstly (obviously) all particles would be exchanged for antiparticles. That means that in the star, anti-protons would fuse to anti-helium releasing electron-neutrinos (as opposed to our sun releasing anti-electron-neutrinos)
    [this is an effect of the weak interaction]

    note also: a poton is it's own antiparticle, this the stars would shine just like ours do.
    gravity wise you wouldn't be able to tell the difference either. paricles and anti-particles have the same gravitational mass...

    I'm sorry but I don't t

  • Yum (Score:5, Funny)

    by sporty ( 27564 ) on Friday July 25, 2003 @07:20AM (#6530516) Homepage
    Just don't put the pasta near the anti pasta. That could be bad.

    /rimshot

  • just do it, worry more about the plot.. (Score:4, Insightful)

    by gl4ss ( 559668 ) on Friday July 25, 2003 @07:36AM (#6530558) Homepage Journal
    it doesn't REALLY matter if theres some sillyness from physics point of view(hyperjump is one) as far as the book tells a good story and is intresting otherwise, has good flow of text and other things that make a book a great book. keep the sillyness logical and constant though, _DON'T_ fall into explaining every little tidbit how it works and how it is possible unless it's essential from viewpoint of some character in the book(or similar).

    most great scifi books/ short novels could have been just as easily setted in non typical scifi setting(heinleins starship troopers could be set without much fuss into ancient greek), bad scifi is where the 'scifi' is used just to cover up something else, like the lack of plot or bad writing. though, one can use the story to tell of a world to come and it can work pretty well, and predict possibilities of technology, but without good storytelling these are just academical papers on possible future.

    and most things that apply to scifi apply to fantasy too, mostly because underneath they are pretty much the same for most authors, it doesn't really matter if the lockpick is a complicated electronic hacker gadget or a spell, or if you use a robot instead of a demigod as an ageless being watching over humanity for thousands of years.

    • sillyness from physics point of view(hyperjump is one)

      An antihyperjump moves you a very short distance?
      Or it moves you a very great distance in a time longer than it would take to travel there in real space?

  • Some differences (Score:5, Funny)

    by Lady Jazzica ( 689768 ) on Friday July 25, 2003 @07:37AM (#6530564)
    There are a few differences between an antimatter galaxy and a matter galaxy like our own. For instance, in an antimatter galaxy, the element Antimony is called "Mony". They use it as a means of facilitating the exchange of goods and services. Also, in antimatter England, they drive on the right side of the road.
    • > There are a few differences between an antimatter galaxy and a matter galaxy like our own. For instance, in an antimatter galaxy, the element Antimony is called "Mony". They use it as a means of facilitating the exchange of goods and services.

      So you're saying Billy Idol, to say nothing of Tommy James and the Shondells, were just a bunch of greedy aliens from this other galaxy?

      Oh, right. Roswell 1947, shortly before the popularity of rock 'n' roll... and the rise of RIAA to world dominance. It a

    • Also, in antimatter England, they drive on the right side of the road.


      "Be careful with that [matter inversion gizmo]... we could end up undoing unthings untogether!

      -- Doctor Who, John Pertwee

  • Strong constraints exist from gamma rays (Score:5, Interesting)

    by pfdietz ( 33112 ) on Friday July 25, 2003 @07:38AM (#6530566)
    Observation of annihilation gamma rays places strong constraints on the amount of antimatter in the universe. For example, we can confidently say that most of this galaxy is normal matter. Were this not the case, annihilation of matter and antimatter gas in interstellar space would produce too much annihilation radiation at 511 keV (electron/positron annihilation) and at ~100 MeV (photons from neutral pion decay.)

    IIRC, the smallest scale at which antimatter can dominate is galactic superclusters, but even that may now be ruled out.

    • IIRC, the smallest scale at which antimatter can dominate is galactic superclusters, but even that may now be ruled out.

      I just wanted to respond to back this up; at least as of the mid-90's, you'd have to go out beyond the Local Supercluster. I haven't followed this since then, unfortunately, so I don't know what the implication of the current (GRO?) data is.


    • If instead of one big bang, in this universe, there were several, 100 billion light years apart. The universes would each cease to exist before they could detect each other...

  • couple of things (Score:4, Interesting)

    by alexjohns ( 53323 ) <[moc.liamg] [ta] [cirumla]> on Friday July 25, 2003 @08:41AM (#6530857) Journal
    There are no anti-photons so light from anti-matter stars looks the same as from regular stars. So you wouldn't be able to tell from that. However, somewhere there would be an interface of some sorts. A boundary where on one side is anti-matter and the other matter. This isn't a hard boundary, but if you have two galaxies, about half-way in between there would be a lot of shit going on.

    See, empty space isn't really empty. There's Hydrogen out there. There would be an amazing light show at the border. The constant meeting of matter and anti-matter (space dust, if you will, emitted by both galaxies) would most likely be very visible. Matter/anti-matter reactions are very energetic, far more so than fusion, even.

    The only way to have anti-matter galaxies in your universe is if they were more than 13.7 billion light years distant, so the light from the interface hasn't reached us yet. Or maybe there could be a single anti-matter galaxy somewhere out there, discovered by the weird light reaching us from that corner of the universe. I doubt our telescopes have looked everywhere, yet.

    Aside from all that, science is just a hook. As long as you're internally consistent, it doesn't matter if your science is far-fetched. Plot, characters, story. Interesting things happening to interesting people will be what sell books. I probably didn't need to tell you that. I still read a lot of old sci-fi that has bad science in it. 'Lensmen', Heinlein juveniles like 'Tunnel in the Sky', 'Citizen of the Galaxy', and 'Starman Jones', Campbell's 'Arcot, Morey, and Wade' stories. Love that stuff.

    • I am suggesting this as a story line, not as real physics, but since we are seeing signs that dark matter/energy exhibits a repulsive force of some kind, how about if dark matter was "neutral matter" that did not react with M or A-M except through it's repulsive force. This could implement the buffer between the M and A-M galaxies and explain the lack of observed annihilation events between the galaxies.

      Just an idea...

  • Nobody here reads Greg Bear? (Score:4, Interesting)

    by borgboy ( 218060 ) on Friday July 25, 2003 @08:58AM (#6530983)
    In Anvil of Stars, Bear introduces a civilization so advanced that they could manipulate vast ammounts of matter over large distances and convert M objects to A-M. Including people. The human's who were converted to A-M died slowly because their organic chemistry was subtly different. Made for a nasty suprise when the pilots tried to re-dock with their mother ship.

    Not that this represents anything based in reality or the laws of physics. Just "prior art" from a respected hard sci-fi writer.
    • Another fun trick for someone with an advanced enough technology would be to rotate someone in 4D space, so their left and right are switched.

      I am quite curious as to how this would alter their perception. Would everything look backwards to them?
  • Matter vs. Anti-Matter

  • So, (Score:2)

    by pmz ( 462998 )
    in this anti-galaxy, would there be anti-comedians? Would everyone's boss be an anti-asshole? I'm getting dizzy...
  • First, let me say IANAP. I'm also basically brainstorming; if this, then maybe that.

    So... what is antimatter? It's matter whose particles have an opposite charge from the particles we know as matter. A matter proton has a positive charge. An antimatter proton (negaton?) has a negative charge. A matter electron has a negative charge. An antimatter positron has a positive charge.

    What would antimatter be like?

    The first thing I can think of is that antimatter electricity (positricity?) will flow in the oppos

    • Here's something to think about that follows: light emitted by antimatter, because the electric and magnetic fields are generated in reverse, would be inverted in frequency/wavelength.

      I have no idea what you mean by "inverted in frequency/wavelength." However, the truth is that light would be perceptibly unaffected. As correctly noted by several people here, the photon is its own antiparticle. Or, if you wish to think in terms of E-M waves, changing the sign of the E- and B-fields in an electromagne

      • Hmm... yes, a phase shift makes more sense.

        Remember, I qualified my post that I was brainstorming. Clearly my storm fizzled out. ;)

        Of course... it would be fun sci-fi to conjecture that the light would be reversed.........
    • The first thing I can think of is that antimatter electricity (positricity?) will flow in the opposite direction. All things that depend upon the charge of electricity, for example, say, magnetic attraction, will be reversed. Matter north would attract antimatter north, and repel antimatter south, and vice-versa.

      Also, electromagnetism would be reversed. With matter, magnetic fields generated by an electric current follow the left-hand rule. Magnetic fields generated by a positric current would follow the r
  • WE are the antimatter...
  • "Geometry, Relativity, and the Fourth Dimension," one possibility is that antimatter galaxies would appear to run backwards in time. Of course, to them, we'd appear as if we were running backwards in time. I'm sure you can build some neat ideas off of this.
  • In my upper-division cosmology classes I recall having a dicussion about this very question. It wen something like this (If my brain doesn't fail me):

    Astrophysicists had seriously toyed with the question of wether other galaxies were anti-matter. Indeed, based off of EM radiation (light), there would be no way to tell, since matter and anti-matter both emit light.

    Also, if the matter between them never interacted, there would be no way to tell, as matter and anti-matter are indistinguishable when complet
  • The anti-particle of a photon is a photon.
  • You mean anti-stars, like Celine Dione?
  • You might check out Nobel Laureate (Physics 1970) Hannes Alfvén's speculations on the matter (or antimatter). Particularly "Worlds-Antiworlds: Antimatter in Cosmology" where he supposed that matter and antimatter stars coexisted with boundary layers of plasma between them. In fact he had a running bet that Alpha Centari was made of antimatter (I once had lunch with him and heard this first person).
    To quote http://www.agu.org/sci_soc/alfven.htm :
    "Some of Hannes Alfvén's ideas are still controversia
  • Although anti-matter sounds cool, proposing a universe/galaxy made entirely of anti-matter really isn't any different than a universe/galaxy of matter. What makes anti-matter anti- is that it's electric charge is reversed (or, if you ask Feynman, it's moving backwards through time--but don't get any funky ideas from that, because the 2nd Law of Thermo still guarantees that even for anti-particles entropy will increase, which is what is really driving time in the direction we call foreward). So, since anti
    • Actually,
      There are anti-neutrons - the parameter that changes is spin, IIRC.

      As for visiting an anti-matter galaxy, you would be mostly fine (probably just a lot more radiation from interstellar particles eroding your ship's hull. Just don't try to land on a planet.

      • There are anti-neutrons - the parameter that changes is spin, IIRC.

        No - neutrons have a half unit of spin, and the spin of a neutron can be "up" or "down", just as with other half-spin particles such as electrons and protons. The same is true of anti-neutrons, so a neutron and an anti-neutron can have the same spin (both "up" or both "down") or can have opposite spins (one "up", one "down").

        It's other charge-like quantum numbers, such as baryon number [wolfram.com] and isospin [wolfram.com] (unrelated to spin), that change in the n

    • there is no such thing as an anti-neutron That depends on what theory you subscribe to. One theory states that a neutron is composed of an electron and a protron. This is backed up by three observations: 1) Its mass is equal to the sum of the two. 2) It has no net charge (the charges cancel). 3) When a neutron is split apart, an eletron was observed "flying out." This is this true then although the net result is the same--a particle with no NET charge--a neutron and anti-neutron would still be different
      • Actually, by suggesting that the mass of a neutron is the sum of the masses of an electron and a proton, you're dodging one of the really fun little divergences in subatomic physics. There's actually a really tiny difference between M(n) and M(p) + M(e). Something like three or four orders of magnitude smaller than an electron, but the difference is there.

        His name is Neutrino. His mass is real, but he is not.

        • Actually, by suggesting that the mass of a neutron is the sum of the masses of an electron and a proton, you're dodging one of the really fun little divergences in subatomic physics. There's actually a really tiny difference between M(n) and M(p) + M(e).

          ...just as there's a difference between the mass of a hydrogen atom and the masses of the electron and nucleus - equal to the energy it requires to ionize the atom, I think. Conservation of energy and all that.... The same applies to the mass of, say, a

    • matter / antimatter is not just a charge difference, and its not true that non-charged particles don't have anti-particles. consider neutrinos.

      and of course there is a anti-neutron - what do you think you would get when a anti-proton and positron fuse ? Hadrons are made up of quarks and these have corresponding anti-quarks - from which you get not just anti-proton but also neutron and anti-neutron.
  • It's obvious you've never read any of the "expanded" Star wars universe books. If you did, you'd already know that the dark side of the force is fueled by "every living thing made of anti-matter."

    Dumbass!




    Sarcasm impaired people please note that this was intended to be a bad joke.
  • Hrm. I was just thinking... when the cosmologists estimate the "age of the universe" and they say that the limit of what we can see is, oh, say 13 billion light years, do they account for the time it took for the source of said radiation to get out that far in the age of their universe? Since (supposedly) matter cannot travel anywhere near the speed of light, the universe must be several orders of magnitude older than the "oldest" light we can see, and the things we are "seeing" are really outside the edge
  • Maybe I'm showing my age here, but anyone who remembers DC Comic's Crisis on Infinite Earths [dccomics.com] from the 80s knows that the primary difference between regular matter and anti-matter universes is that the anti-matter universe is EVIL!!!
  • Check out Robert Forward's "Time Master" for an interesting read on Negative Matter. (Not the same as Anti-matter.) It has repulsive instead of attractive gravity, it annihilates itself with matter producing zero energy and a bunch of other cool properties. And aparently, there is strong theoretical evidence that it might exist too.
  • I wonder what would happen if a anti-blackhole collided with a normal blackhole. Would they eat eachother up instantly, or blow up? Would the bigger blackhole simply become that much less massive? Or what about dark-matter coming in contact with anti-matter, is that even possible?
  • Your story has got me thinking. It is suspected that gamma ray bursts may be caused by the merger of two blackholes. A large gamma ray burst is so energetic that it can emit more energy for a few milliseconds than every other radiant object in the universe combined. But what would happen if a blackhole merged with an anti-blackhole? There would still be the huge outpouring of energy because this is evidently due to effects manifested outside the event horizon. However, what happens after the matter and the
    • Warning: my physics is several years out of date. That said... every singularity is its own antisingularity. That is to say, you cannot tell a difference between a black hole formed by conventional matter collapse and a black hole formed by antimatter collapse.

      If a matter singularity and an antimatter singularity collided, we don't know what would happen. For all we know, mutant space hamsters fly out of their nether orifices. It all happens inside the event horizon; we can't see it, can't experience i
      • you cannot tell a difference between a black hole formed by conventional matter collapse and a black hole formed by antimatter collapse.

        I was about to argue this point but I just read it again slowly and see now that it is technically correct. You can't tell the difference from the outside. However just because some form of matter passes that point which we call the event horizon doesn't mean that anything magical happens to it. I read just recently that someone, Hawking I think, proved that if you fell i

        • I would like to see references for this.

          Einstein's General Theory of Relativity. The Special Theory only relates mass with spacetime distortion; the General Theory has the mass-energy equivalence.

          If you know the name of the governing equation that relates gravitational force to electromagnetic energy density please tell me because I would be fascinated to read about it.

          E = mc**2. Or, E / c**2 = m.

          Or, g = (E1/c**2)*(E2/c**2) / d**2.

          Googling for "energy distorts spacetime" returns a couple of refere

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