
Morphing neutrinos provide clue to antimatter mystery - okket
http://www.nature.com/news/morphing-neutrinos-provide-clue-to-antimatter-mystery-1.20405
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runeks

        > Why the Universe is filled with matter, rather than 
        > antimatter, is one of physics’ greatest mysteries.
    

Why do we assume there is no anti-matter just because we can't observe it? Our
sensory organs were developed to survive on this planet. They're made out of
matter and evolved to detect the presence of matter. And when we make a
detector it's made out of matter too.

I don't think it's farfetched to assume that matter-antimatter collisions
occur all the time; they're just not that spectacular. It may even be a bit
presumptuous to assume that it's even possible for matter to ever detect the
presence of anti-matter. Because, detecting the presence of anti-matter just
constitutes looking at the radiation left behind by a "collision" with matter.
That's not observing anti-matter, it's an after-the-fact conclusion, that
there must had been anti-matter before the radiation in question appeared. As
soon as matter _observes_ / _comes in contact with_ anti-matter, it's no
longer matter. So matter, in and of itself, seemingly cannot observe anti-
matter (because it's transformed into something else at the moment it does).

Reading Wikipedia, it also appears that the matter/anti-matter relationship is
asymmetric:

Bondi pointed out that a negative mass will fall toward (and not away from)
"normal" matter, since although the gravitational force is repulsive, the
negative mass (according to Newton's law, F=ma) responds by accelerating in
the opposite of the direction of the force. Normal mass, on the other hand,
will fall away from the negative matter. _He noted that two identical masses,
one positive and one negative, placed near each other will therefore self-
accelerate in the direction of the line between them, with the negative mass
chasing after the positive mass._ Notice that because the negative mass
acquires negative kinetic energy, the total energy of the accelerating masses
remains at zero. Forward pointed out that the self-acceleration effect is due
to the negative inertial mass, and could be seen induced without the
gravitational forces between the particles. \---
[https://en.wikipedia.org/wiki/Anti-
gravity#General_relativit...](https://en.wikipedia.org/wiki/Anti-
gravity#General_relativity_research_in_the_1950s)

Fascinating stuff!

~~~
dogma1138
We know that there is no or very little anti matter in the universe because
things are not blowing up, we also know that matter and anti matter have been
created in equal amounts, hence were looking into what the frak happened to
all the anti matter.

Also anti matter reacts to the fundamental forces just like any other matter.

It doesn't produce anti mass, anti gravity or anti anything.

It does have an opposite charge and spin off its normal matter counterparts
but other than that its pretty boring.

weve made anti hydrogen, oxygen is pretty big so it would take a while before
we can make anti water but it will be done also most likely.

~~~
runeks
I guess I stand corrected on some points, but Wikipedia seems a lot less
certain than you regarding anti-gravity.

    
    
        > Antihydrogen atoms should be attracted to other matter 
        > or antimatter gravitationally with a force of the same 
        > magnitude that ordinary hydrogen atoms experience.     
        > This would not be true if antimatter has negative 
        > gravitational mass, which is considered highly unlikely, 
        > though not yet empirically disproven (see gravitational 
        > interaction of antimatter).
    

I'm not sure what the exact meaning of "highly unlikely" is in this context.

[https://en.wikipedia.org/wiki/Antihydrogen#Characteristics](https://en.wikipedia.org/wiki/Antihydrogen#Characteristics)

[https://en.wikipedia.org/wiki/Gravitational_interaction_of_a...](https://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter)

~~~
dogma1138
Gravity is the result of matter(or energy) interacting (bending) spacetime.
All massive objects bend space time hence they generate gravity, the mass of
an anti proton is exactly the same as that of a proton. We haven't observed
full gravitational interactions because we only create tiny amounts of anti
matter, and even less of molecular anti matter. Since all anti matter must be
kept in vacuum and electro magnetic containment it's a bit hard to check how
does anti mater works with gravity. There are very little frameworks where
anti matter actually interacts differently with gravity and hence space time.
Even MTOG theories tend to treat anti matter in the same manner, it has a
positive mass (we can verify that), if it has a positive mass it also has a
positive energy, if it has that it should interact with gravity in the same
manner as any other massive object.

