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ALPHA observes light spectrum of antimatter for first time

phys.org

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Re: ALPHA observes light spectrum of antimatter for first time

#11

Post by jcoffland »

cshimmin wrote: post #8
ianai wrote: post #3

I remember Feynman said to check the spin of the photons emitted from alien species. If they're 90 degrees out of phase with ours then they're made of antimatter and we shouldn't shake hands. (At least I think it was spin, been a while since I read QED)

Actually his story was about trying to explain the difference between left and right in terms of nuclear spin experiments. You also explain that humans greet by shaking their right hands. If you meet the alien and he extends his left hand to shake, he must be made of antimatter (since the combination of parity and antimatter conjugation is a symmetry of the universe). edit: jess is correct, and that's the whole point…

Assuming a two handed alien of course.

Re: ALPHA observes light spectrum of antimatter for first time

#12

Post by jessriedel »

hughes wrote: post #4

> Antihydrogen is made by mixing plasmas of about 90,000 antiprotons from the Antiproton Decelerator with positrons, resulting in the production of about 25,000 antihydrogen atoms per attempt. Antihydrogen atoms can be trapped if they are moving slowly enough when they are created. Using a new technique in which the collaboration stacks anti-atoms resulting from two successive mixing cycles, it is possible to trap on…

To help appreciate the difficulty: Antimatter can only be created from matter by smashing it together with enough energy to spontaneously produce matter-antimatter pairs (more or less). The amount of energy to create an antiproton is about a billion electron volts, while the binding energy to split a hydrogen atom (or antiatom) apart is just 13 electron volts. So you have to cram this fantastic amount of energy into individual particles, then cool them down by 8 orders of magnitude without touching them (to avoid annihilating them).

Re: ALPHA observes light spectrum of antimatter for first time

#14

Post by jessriedel »

cshimmin wrote: post #8
ianai wrote: post #3

I remember Feynman said to check the spin of the photons emitted from alien species. If they're 90 degrees out of phase with ours then they're made of antimatter and we shouldn't shake hands. (At least I think it was spin, been a while since I read QED)

Actually his story was about trying to explain the difference between left and right in terms of nuclear spin experiments. You also explain that humans greet by shaking their right hands. If you meet the alien and he extends his left hand to shake, he must be made of antimatter (since the combination of parity and antimatter conjugation is a symmetry of the universe). edit: jess is correct, and that's the whole point…

> combination of parity and antimatter conjugation is a symmetry of the universe

It's only an approximate symmetry. Look up CP symmetry violations.

Re: ALPHA observes light spectrum of antimatter for first time

#15

Post by hossbeast »

jcoffland wrote: post #11
cshimmin wrote: post #8

Earlier quoted context omitted.

Actually his story was about trying to explain the difference between left and right in terms of nuclear spin experiments. You also explain that humans greet by shaking their right hands. If you meet the alien and he extends his left hand to shake, he must be made of antimatter (since the combination of parity and antimatter conjugation is a symmetry of the universe). edit: jess is correct, and that's the whole point…

Assuming a two handed alien of course.

Many handed

Re: ALPHA observes light spectrum of antimatter for first time

#17

Post by plandis »

PavleMiha wrote: post #7
colechristensen wrote: post #5

Earlier quoted context omitted.

>consistent with the Standard Model Is generally one of the most disappointing phrases one can read in science news. Hooray for progress and all, but everybody is hoping for exactly the opposite result.

Maybe we're running out of surprising things.

Lord Kelvin said something similar in 1900 about there being nothing left to discover. Within 30 years quantum mechanics would be discovered/created.

Re: ALPHA observes light spectrum of antimatter for first time

#18

Post by lutorm »

josho wrote: post #16

Simply amazing. I still thought antimatter was a theory. Can anyone recommend a book on this topic for the layman?

Not a theory at all. You get antimatter out of many common radioactive materials: https://en.wikipedia.org/wiki/Positron_emission

It's the building atoms out of it that's tricky, but antimatter is nothing new.

Re: ALPHA observes light spectrum of antimatter for first time

#19

Post by lutorm »

jessriedel wrote: post #13
nonbel wrote: post #9

Dumb question: Is it easier to create antimatter if you already have some? I mean using it as a nucleation point, or perhaps energy source.

Nope. It's a sensible question, but it doesn't help.

It would be easier if you could build your entire experimental apparatus out of antimatter, but if you could do that you're probably beyond making experiments with single atoms of it... ;-)

Re: ALPHA observes light spectrum of antimatter for first time

#20

Post by mikeash »

lutorm wrote: post #19
jessriedel wrote: post #13

Earlier quoted context omitted.

Nope. It's a sensible question, but it doesn't help.

It would be easier if you could build your entire experimental apparatus out of antimatter, but if you could do that you're probably beyond making experiments with single atoms of it... ;-)

I would not want to be in charge of filing the Environmental Impact Statement for such a facility.
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