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I have an idea for a Sci-Fi story that involves a planet with a third moon made entirely of antimatter, before I delve further into this concept, I would appreciate input on

  • how to make this scientifically feasible (if possible)?

  • Apart from a lack of atmosphere, what else would I need to do to make it realistic and believable?

    And

  • I also need a safe and scientifically sound way to harvest and collect this resource, since any regular matter that comes in contact with the moon will explode. Any ideas on how to harness this?

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  • $\begingroup$ Sure why not but I don't know how the antimatter moon will interact with the matter planet gravitationally assuming no foul play(remember these two stuffs want to kill off one another on contact) $\endgroup$
    – user6760
    Sep 16, 2017 at 3:45
  • $\begingroup$ I would split this question in two, else it can be too broad $\endgroup$
    – L.Dutch ♦
    Sep 16, 2017 at 4:39
  • $\begingroup$ Spray the moon with a gas. This turns its surface to plasma, which can be removed with a magnetic scoop. $\endgroup$
    – Donald Hobson
    Sep 16, 2017 at 11:22
  • $\begingroup$ More on antimatter at link 'We can't see antimatter but it really does matter' $\endgroup$
    – Justin Thyme
    Sep 16, 2017 at 15:43
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    $\begingroup$ @L.Dutch I disagree. Sometimes very broad questions can lead to very specific, usable answers. Questions do not need to be 'graspable' by everyone in order to be useful to many. Besides, there are no real specifics about antimatter questions yet, they have not been explored enough. Almost everything is conjecture. Too much specification about antimatter just becomes science fiction, not science. $\endgroup$
    – Justin Thyme
    Sep 16, 2017 at 15:52

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  1. Your antimatter moon will need a magnetic field to block the solar wind.
    solar wind schematic from https://infograph.venngage.com/p/230803/magnetic-field-infographic

Otherwise particles of matter blown into the moon will react it away. Probably occasional particles will still get through and react. Your antimatter moon can be made of anti-iron to facilitate making that magnetic field, just as the earths iron core makes the earths magnetic field. Anti - iron will also be helpful for #3.

  1. Blast mining. There is no good way to get machines down onto this moon to mine. Maneuvering jets would expel gases and cause explosions. But you can blast pieces off of your moon from a distance by firing in kinetic projectiles. The antimatter / matter reaction itself might be enough to launch bits of antimatter up off the moon. Or the projectiles can have explosives. Once little pieces are blasted into space they will be easier to deal with.

  2. Magnetic manipulation. This is where it is handy for the moon to be anti-iron. You could capture and keep your piece of anti-iron in an airless storage room using electromagnetic levitation

electromagneticaly levitated red hot ball

For metallic melts electromagnetic levitation provides an elegant method of noncontact containerless measurement, eliminating most interactions between the sample and its environment. This technique has been used in the past mainly for the study of highly reactive melts at high-temperatures. The sample, assuming a simple spherical shape, is contained in a clean environment and can be studied over a large temperature range. Temperatures again have to be measured with a pyrometer. An electromagnetic levitation device employs inhomogeneous radio-frequency electromagnetic fields to heat and position the samples. Such a field has two effects on a conducting, diamagnetic body. First, it induces eddy currents within the material, which, due to ohmic losses, eventually heat up the sample by inductive heating, and second, it exerts a Lorentz force on the body, pushing it towards regions of lower field strength. The latter effect can be used to compensate the gravitational force.

Safe in its magnetic levitation coil you could bring your piece of anti-iron home and use it for all your antimatter needs.

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  • $\begingroup$ This is absolutely perfect! Just what I needed, thank you so much! I was a little worried by some of the more discouraging answers, but your creative idea even helps counter the argument of meters above, magnetic is exactly how it would be protected best, and the idea of blasting pieces off it is indeed much more practical than mining. $\endgroup$
    – Stacey Heather Silverman
    Sep 16, 2017 at 4:19
  • $\begingroup$ Yes the matter antimatter reaction will make a big explosion. Even sending nukes of the same size wouldn't make it much bigger. $\endgroup$
    – Donald Hobson
    Sep 16, 2017 at 11:14
  • $\begingroup$ @StaceyHeatherSilverman If will's answer is "absolutely perfect!" try using the accept answer button to show that. It is generally not necessary or appreciated by the community at large to post comments that simply say how good a post is, that is what the upvote and accept buttons are for. (Plus both of them give rep) $\endgroup$
    – Braydon
    Sep 16, 2017 at 14:50
  • $\begingroup$ OK, thanks for the tip, I'm brand new here and this is my first question so any helpful tips are welcome, thank you for taking the time to give advice $\endgroup$
    – Stacey Heather Silverman
    Sep 16, 2017 at 16:33
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    $\begingroup$ Is that the green check button BTW? Its the only other thing I see to click on besides the upvote buttons $\endgroup$
    – Stacey Heather Silverman
    Sep 16, 2017 at 16:35
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Not realistic, unless perhaps it was recently (on an astronomical time scale) created by some technologically advanced race. The problem is meteor impacts. If you look at the moon, or any similar body, you'll see that it's covered with craters.

Those craters were created just by the kinetic energy of the impacting meteor - (mv^2)/2, where m is the mass of the meteor, and v is probably a max of about 40 km/sec. Now compare that to the annihilation energy of a normal matter meteor reacting with the antimatter moon - 2 * mc^2, where c is 300,000 km/sec. That's what, potentially 20 million times greater? (Potentially because some of the antimatter might be blown into space instead of annihilating immediately.) You're also likely to get lots of radiation and charged particles created by the reaction...

So an antimatter moon would soon be blown to bits by meteor impacts, and the side effects of the process would not be beneficial for anything in the same solar system.

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Is it realistic - No. Very, very much no. Planets all form from the same disk, so having one moon be antimatter while everything else is regular matter is... not exactly plausible. There are a small handful of ways that an extrasolar object could be captured, but stars form in groups - of largely the same matter - And galaxies also generally comprise of the same matter. So an antimatter object would really have to be extra-galactic. Capturing an extra-galactic object as a moon is leaps and bounds more unlikely and difficult.

Now, beyond that - Is an antimatter "Moon" possible to exist? In short: Yes. Antimatter behaves largely like regular matter. And, actually, being planet-sized helps it survive. If it's a large moon or planet, it can have a magnetic field capable of deflecting enough of the solar wind and other particles. It can also have an atmosphere, made of anti-matter as well.

Mining would be... interesting, but possible. Much of mining is done with explosives - Something that wouldn't really be needed with a planet of antimatter. Drop something onto it. It explodes. At that point, you can use magnetic fields to capture the objects. Containing and securing them would be difficult, but not impossible.

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  • $\begingroup$ I'm not sure we know enough to say it HAS to be exogalatic. Generally a galaxy should be only one kind of matter. But is there a rule that excludes the possibility of a rare antimatter solar system in a matter galaxy? $\endgroup$
    – Braydon
    Sep 16, 2017 at 3:41
  • $\begingroup$ meteor collisions would be interesting, all explosions are about 2 billion times bigger. $\endgroup$
    – Donald Hobson
    Sep 16, 2017 at 11:18
  • $\begingroup$ Antimatter is created on earth all the time from purely natural phenomena, so yes antimatter and matter CAN be created the same solar system. Even solar flares have antimatter. link The CREATION of the antimatter planet is of no particular concern, it could be theoretically created in our solar system, but PRESERVING and protecting it, aye, there is the rub. It would have to be completely encapsulated so nothing could get in or out - including us. So what purpose would it have? Perhaps as an energy source. $\endgroup$
    – Justin Thyme
    Sep 16, 2017 at 14:47
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A celestial body made of antimatter is entirely plausible.

The interaction of antimatter with gravity was not confirmed experimentally, but the assumption is that antimatter is pulled by gravity in the same way that matter is. If this is the case, then an antimatter moon could orbit a planet made of matter.

Aside from having an opposite electric charge, antimatter would in theory have the same properties as its matter counterpart. Collision between matter and antimatter produces new particles (normally photons, the light particle, though other particles can be produced); this process is known as Annihilation. I assume that the antimatter moon would naturally lose mass and emit light from the asteroids that come in contact with it. An alien civilization could take advantage of this by harnessing the light from space (they would probably get more energy from harnessing a star), or (let's be crazy) by forcing the moon to produce exotic particles, which could be siphoned from space as well. Of course, annihilation would slowly consume the antimatter moon until there is nothing left of it.

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Apparently, anti-matter is produced constantly on earth in intense thunder storms.

link

However it does not last very long.

So, if one believed that antimatter could not be produced from natural causes on earth, you would be wrong.

This is only to emphasize that we really don't know that much about what we know about physics, after all. I had a colleague who said "If the physics book is thick enough, anything can be conjectured." Basically, she meant that we really are not aware of all the totality of information about physics that is currently known, and no where is there a physics book that contains all of the information we have available. And a lot of it is very surprising, indeed.

But it really begs the question be asked, 'How would we detect such a planet in the first place, since we would only perceive it through annihilation?'

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  • $\begingroup$ Why would we only perceive it through annihilation? Antimatter is not invisible, actually it looks almost exactly like normal matter. I think you may be confusing antimatter and dark matter. $\endgroup$
    – Braydon
    Sep 16, 2017 at 3:37
  • $\begingroup$ @Braydon I think the idea here is that it does look like normal matter, so you won't know that what you're looking at is antimatter until you land on it and cause a huge explosion... $\endgroup$
    – akaioi
    Sep 16, 2017 at 3:58
  • $\begingroup$ @akaioi Well I hope you send a probe first. $\endgroup$
    – Braydon
    Sep 16, 2017 at 4:04
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    $\begingroup$ @Braydon I'm reminded of an anecdote from one of Niven's Known Space books. The puppeteer aliens would sell ships with hulls guaranteed to stand up to anything. An explorer landed on an antimatter planet with ... well ... mixed results. Shortly thereafter the puppeteers changed their marketing collateral to say "stands up to anything ... except antimatter" ;D $\endgroup$
    – akaioi
    Sep 16, 2017 at 5:33
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    $\begingroup$ You would see continued small explosions from the surface as meteorites and other incoming particles detonated when they touched the surface. $\endgroup$
    – Willk
    Sep 16, 2017 at 14:30
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'Cards on the table, few physicists believe that such “antigravity” effects exist – that if you released one of those antiprotons and somehow ensured it free passage through the hostile world of matter, it would magically float up. But the recalcitrant nature of antimatter means we’ve never done the experiments, and until we do, we simply don’t know. “Progress is often made by asking the questions we think we already know the answer to,” says Daniel Kaplan of the Illinois Institute of Technology in Chicago.'

from 'Antigravity: Discovering if antimatter falls upwards' link

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