Didn't expect different, but the insane amount of work to make a sufficient amount of antihydrogen to try this with is impressive. The little magnetic trap fidelity to prevent the atoms from...
Didn't expect different, but the insane amount of work to make a sufficient amount of antihydrogen to try this with is impressive. The little magnetic trap fidelity to prevent the atoms from annihilating is a super cool technology.
I wonder, does this completely kill the one electron universe postulate? That idea was always just an interesting thought experiment, not a serious hypothesis, as far as I know. But if positrons...
I wonder, does this completely kill the one electron universe postulate? That idea was always just an interesting thought experiment, not a serious hypothesis, as far as I know. But if positrons were in fact electrons traveling backwards in time, wouldn't that mean that they, and other antimatter particles, would fall upward?
I admittedly spent like an hour pondering your question, but here's what I came up with: Time reversal doesn't mean repulsive gravity. If you consider a falling electron on Earth, and then...
I admittedly spent like an hour pondering your question, but here's what I came up with: Time reversal doesn't mean repulsive gravity. If you consider a falling electron on Earth, and then consider the same motion but with (t) goes to (-t), you still have an electron but now the interpretation is that the electron has been "thrown" up into the air rather than falling. Both situations are perfectly valid motions in a gravitational field. This is not repulsive behavior because the "thrown" electron is still going to slow down as it gets higher and higher just like a baseball thrown in the air does. Truly repulsive gravity would mean the particle accelerates away from the Earth going faster and faster though the acceleration eventually goes to zero.
To summarize: Time reversal for attractive gravity just means the same trajectory with two different initial conditions. This is distinct from repulsive gravity which results in an entirely different trajectory.
As far as gravity is concerned, a positron has the same mass (or nearly the same mass) as an electron. For the precision of this experiment, you can definitely treat their masses as equal and...
As far as gravity is concerned, a positron has the same mass (or nearly the same mass) as an electron. For the precision of this experiment, you can definitely treat their masses as equal and positive. Newtonian gravity still is valid here and you would get the classic -G m_1 m_2/r^2 attractive force between the earth and the positron, which both have positive masses.
The one electron universe is an old idea that may have sparked the more accurate understanding of how particles actually work in quantum field theory. In the current understanding, electrons and positrons are indeed excitations of the very same field across the universe. This doesn't mean that we can only see one electron/positron at a particular time slice.
Yeah, it would be nice, but I think Deimos wants a mostly Javascript-free Tildes, and fast load times. So things like MathJax would be counter to that design philosophy. I think there was some...
Yeah, it would be nice, but I think Deimos wants a mostly Javascript-free Tildes, and fast load times. So things like MathJax would be counter to that design philosophy.
I think there was some Slack extension render LaTeX client-side and be completely transparent to people without the extension. Perhaps that is a solution we can make if there's enough interest in the Tildes community.
Looking into it on Math Stack Exchange, they use MathJax. I'm not sure how hard that would be to implement but they're wrapping the math stuff in $ symbols, I don't think that's used by any other...
Looking into it on Math Stack Exchange, they use MathJax. I'm not sure how hard that would be to implement but they're wrapping the math stuff in $ symbols, I don't think that's used by any other formatting here.
Yeah, wrapping math in dollar symbols is the way to go. So $\sum_{n=1}^{\infty}\frac{1}{n^{2}}=\frac{\pi^{2}}{6}$ rendering on Tildes correctly would be pretty sweet.
Yeah, wrapping math in dollar symbols is the way to go. So $\sum_{n=1}^{\infty}\frac{1}{n^{2}}=\frac{\pi^{2}}{6}$ rendering on Tildes correctly would be pretty sweet.
To note the experimental bound for the difference is <8x10^(-9). R.L. Workman et al. (Particle Data Group), Prog.Theor.Exp.Phys. 2022, 083C01 (2022) and 2023 update https://pdg.lbl.gov/2023/ If...
a positron has the same mass (or nearly the same mass) as an electron
To note the experimental bound for the difference is <8x10^(-9).
R.L. Workman et al. (Particle Data Group), Prog.Theor.Exp.Phys. 2022, 083C01 (2022) and 2023 update https://pdg.lbl.gov/2023/
If the difference was actually nonzero, it'd signify a CPT violation which would be a heck of a discovery.
Of course, I wasn't implying that this experiment or any experiment in our lifetime would measure CPT violation. But the point of experiments like this one is to be agnostic about CPT violation.
Of course, I wasn't implying that this experiment or any experiment in our lifetime would measure CPT violation. But the point of experiments like this one is to be agnostic about CPT violation.
No worries, I wanted to clarify my parenthetical for everyone else anyway. Especially for very structural things about physics like CPT, it's very hard to engage with lay people without sounding...
No worries, I wanted to clarify my parenthetical for everyone else anyway. Especially for very structural things about physics like CPT, it's very hard to engage with lay people without sounding overly authoritative or dogmatic, so I went with a more agnostic viewpoint about the positron mass.
However, any serious local CPT violation proposal would need to be accompanied with an extraordinary overhaul of QFT and modern high energy physics in general. Quite intriguing and interesting if it were true, but any naive modification would break way, way more things than a lay person would realize.
Didn't expect different, but the insane amount of work to make a sufficient amount of antihydrogen to try this with is impressive. The little magnetic trap fidelity to prevent the atoms from annihilating is a super cool technology.
I wonder, does this completely kill the one electron universe postulate? That idea was always just an interesting thought experiment, not a serious hypothesis, as far as I know. But if positrons were in fact electrons traveling backwards in time, wouldn't that mean that they, and other antimatter particles, would fall upward?
I admittedly spent like an hour pondering your question, but here's what I came up with: Time reversal doesn't mean repulsive gravity. If you consider a falling electron on Earth, and then consider the same motion but with (t) goes to (-t), you still have an electron but now the interpretation is that the electron has been "thrown" up into the air rather than falling. Both situations are perfectly valid motions in a gravitational field. This is not repulsive behavior because the "thrown" electron is still going to slow down as it gets higher and higher just like a baseball thrown in the air does. Truly repulsive gravity would mean the particle accelerates away from the Earth going faster and faster though the acceleration eventually goes to zero.
To summarize: Time reversal for attractive gravity just means the same trajectory with two different initial conditions. This is distinct from repulsive gravity which results in an entirely different trajectory.
As far as gravity is concerned, a positron has the same mass (or nearly the same mass) as an electron. For the precision of this experiment, you can definitely treat their masses as equal and positive. Newtonian gravity still is valid here and you would get the classic -G m_1 m_2/r^2 attractive force between the earth and the positron, which both have positive masses.
The one electron universe is an old idea that may have sparked the more accurate understanding of how particles actually work in quantum field theory. In the current understanding, electrons and positrons are indeed excitations of the very same field across the universe. This doesn't mean that we can only see one electron/positron at a particular time slice.
Off-topic, but does anybody know about in-Tildes support for LaTeX/similar systems based on it like e.g. Math Stack Exchange has it?
Yeah, it would be nice, but I think Deimos wants a mostly Javascript-free Tildes, and fast load times. So things like MathJax would be counter to that design philosophy.
I think there was some Slack extension render LaTeX client-side and be completely transparent to people without the extension. Perhaps that is a solution we can make if there's enough interest in the Tildes community.
I'd kill for LaTeX support on Tildes. @Deimos for how difficult it'd be to implement?
Looking into it on Math Stack Exchange, they use MathJax. I'm not sure how hard that would be to implement but they're wrapping the math stuff in $ symbols, I don't think that's used by any other formatting here.
Yeah, wrapping math in dollar symbols is the way to go. So $\sum_{n=1}^{\infty}\frac{1}{n^{2}}=\frac{\pi^{2}}{6}$ rendering on Tildes correctly would be pretty sweet.
To note the experimental bound for the difference is <8x10^(-9).
If the difference was actually nonzero, it'd signify a CPT violation which would be a heck of a discovery.
Of course, I wasn't implying that this experiment or any experiment in our lifetime would measure CPT violation. But the point of experiments like this one is to be agnostic about CPT violation.
Apologies, my comment wasn't to dunk on you or anything, but it made me go look up the experimental bounds and I wanted to share. :)
No worries, I wanted to clarify my parenthetical for everyone else anyway. Especially for very structural things about physics like CPT, it's very hard to engage with lay people without sounding overly authoritative or dogmatic, so I went with a more agnostic viewpoint about the positron mass.
However, any serious local CPT violation proposal would need to be accompanied with an extraordinary overhaul of QFT and modern high energy physics in general. Quite intriguing and interesting if it were true, but any naive modification would break way, way more things than a lay person would realize.