Analogous to matter, but with charge of the particles opposite to their ordinary matter counterparts.
Questions tagged [antimatter]
981 questions
142
votes
13 answers
Is anti-matter matter going backwards in time?
Some sources describe antimatter as just like normal matter, but "going backwards in time". What does that really mean? Is that a good analogy in general, and can it be made mathematically precise? Physically, how could something move backwards in…
Gerard
- 7,189
63
votes
6 answers
What does antimatter look like?
I have seen simulations of antimatter on TV. Has antimatter ever been photographed?
Catzmuze
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63
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5 answers
Do anti-photons exist?
I know what anti-matter is and how when it collides with matter both are annihilated. However, what about anti-photons? Are there such things as anti-photons?
I initially thought the idea preposterous. However I am curious because, if anti-photons…
Dale
- 6,150
57
votes
6 answers
Why is matter-antimatter asymmetry surprising, if asymmetry can be generated by a random walk in which particles go into black holes?
My understanding is the early universe was a very "hot" (ie energy dense) environment. It was even hot enough for black holes to form from photons.
My second point of understanding is that black holes can lose mass due to hawking radiation, which…
Livid
- 1,096
53
votes
3 answers
How would we tell antimatter galaxies apart?
Given that antimatter galaxies are theoretically possible,
how would they be distinguishable from regular matter galaxies?
That is, antimatter is equal in atomic weight and all properties, except for the opposite reverse charge of the particles,…
Soren
- 843
51
votes
3 answers
Why don't electron-positron collisions release infinite energy?
Questions of the form:
An electron and a positron collide with E MeV of energy, what is the frequency of the photons released.
quite often come up in my A Level course (for often fairly arbitrary E). But this got me thinking. There is energy…
DoublyNegative
- 982
45
votes
2 answers
Identification of particles and anti-particles
The identification of an electron as a particle and the positron as an antiparticle is a matter of convention. We see lots of electrons around us so they become the normal particle and the rare and unusual positrons become the antiparticle.
My…
John Rennie
- 367,598
40
votes
4 answers
What color is antimatter?
Salt (NaCl) is white. But what about anti-salt? Assuming it didn't collide with the regular matter and annihilate, and assuming I could look at it, would it also be white? Same for any material/substance. If you replaced the matter (protons,…
chausies
- 1,560
40
votes
1 answer
How close does a particle-antiparticle pair need to be for annihilation to happen?
I've most often seen the statement that the annihilation of a particle and its antiparticle occurs when they 'collide' with one another. So in other words when they get very close to one another right?
How close do they need to be (for annihilation…
docscience
- 11,779
38
votes
3 answers
What happens when anti-matter falls into a black hole?
Let's say a black hole of mass $M$ and a very compact lump of anti-matter (not a singularity) also of mass $M$ are traveling toward each other. What does an outside observer see when they meet?
Will they blow themselves apart in a …
Schwern
- 4,534
36
votes
1 answer
Why was the first discovered neutrino an anti-neutrino?
In the search for neutrinos, Cowan and Reines discovered the electron anti-neutrino and named it as such. Why is the particle they discovered the anti-variety?
The reason we call electrons 'electrons' and not 'anti-electrons' is because the…
Joshua
- 1,373
32
votes
5 answers
Why do or don't neutrinos have antiparticles?
This was inspired by this question. According to Wikipedia, a Majorana neutrino must be its own antiparticle, while a Dirac neutrino cannot be its own antiparticle. Why is this true?
Peter Shor
- 11,536
32
votes
3 answers
Has the gravitational interaction of antimatter ever been examined experimentally?
I know that the gravitational interaction of antimatter is expected to be the same as normal matter.
But my question is, has it ever been experimentally validated?
I think it would not be a trivial experiment, because electromagnetic effects have to…
peterh
- 8,872
31
votes
2 answers
Experimental observation of matter/antimatter in the universe
Ordinary matter and antimatter have the same physical properties when it comes to, for example, spectroscopy. Hydrogen and antihydrogen atoms produce the same spectroscopy when excited, and adsorb the same frequencies. The charge does not make a…
Stefano Borini
- 3,970
30
votes
1 answer
Why is Anti-helium so important in the search for dark matter?
I've been reading/hearing that if the AMS satellite measures a significant flux of anti-helium in cosmic rays, that would be an irrefutable proof of dark matter. I was wondering:
Why is that? what is the dark matter decay/annihilation that produces…
Juanjo
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