this post was submitted on 20 Jun 2023
105 points (100.0% liked)
Science
12955 readers
11 users here now
Studies, research findings, and interesting tidbits from the ever-expanding scientific world.
Subcommunities on Beehaw:
Be sure to also check out these other Fediverse science communities:
This community's icon was made by Aaron Schneider, under the CC-BY-NC-SA 4.0 license.
founded 2 years ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
Some context on axions.
For decades scientists noticed that quantum phenomena respect something called CP-symmetry, that is a really posh way to say "if you sub your particle with an antiparticle and invert its spatial coordinates, the laws of physics will stay the same". So for example it doesn't really matter if you have an electron at (1,1,1) or a positron at (-1,-1,-1), the effect is the same.
There are some exceptions (called CP violations) but for most part CP-symmetry is a real phenomenon. And one of those violations that could happen is when you're dealing with quarks (the junk that protons and neutrons are composed of). And if something can happen, in quantum mechanics, it will happen. So why don't CP violations happen?
Based on that, in 1977 Roberto Peccei and Helen Quinn predicted a new particle, that they named "axion" after some laundry detergent, as "it washed off the problem" (yup - scientists being silly with names, nothing new). That axion particle would be a really small particle, but with mass (unlike photons), and it compensates the predicted CP violation.
Now, to the link: apparently axions are a real thing, and they explain (at least partially) what dark matter is supposed to be.
Can you expand on what "invert its spatial coordinates" means? From your example it seems you're just flipping around the origin of your coordinate system, but since there is no fixed, "natural" reference frame that would provide a "true" origin, isn't that origin completely arbitrary and the math should then work out with any origin you use? I feel like I'm missing something here
Not OP, but: it works similarly to looking at the system in a mirror. The clock's hands turn, well, clockwise, but if you look at the mirror their movement is anticlockwise. Importantly, if you look at that mirror in another mirror, it will be clockwise again. Add yet another mirror and it's anticlockwise.
With a single mirror at position x=0 (and YZ plane), you invert "x" position, so (1, 1, 1) becomes (-1, 1, 1). "Inverting" the spatial coordinates ((x,y,z) -> (-x, -y, -z)) is effectively the same as looking at system through 3 mirrors, located at x = 0 (YZ plane), y = 0 (XZ plane) and z = 0 (XY plane), but that is a bit hard to visualize/arrange in practice so usually you would think of it as an equivalent operation of a point reflection around (0, 0, 0). You are right that the point is arbitrary: the important thing is, among others, that clockwise movement becomes anticlockwise.