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ALPHA observes light spectrum of antimatter for first time

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Re: ALPHA observes light spectrum of antimatter for first time

#51

Post by btouellette »

glandium wrote: post #46

So, if antimatter has the same light spectrum as matter, what makes us theorize that there is currently more matter than antimatter in the universe?

If you're asking how do we know there is more matter than antimatter in the universe the answer is that it is consistent with the observations/calculations surrounding Big Bang nucleosynthesis and CMB anisotropies. If you're asking what do we theorize is the reason there is more matter than antimatter in the universe there isn't a satisfactory answer yet. It's one of the biggest open problems in physics.

Re: ALPHA observes light spectrum of antimatter for first time

#52

Post by odrekf »

duncanmeech wrote: post #28

Stop posting physics articles on hacker news. Just because everyone here has watched too much Star Trek and Star Wars doesn't mean we actually understand a single solitary shred of this stuff...although it sounds cool.

I understood the article, and I'm not a physicist or anything like that. And I suspect almost everyone else here who read it understood it too. It's not uncommon for HN readers to be interested in how the Universe works, and therefore this wouldn't be the first physics article they've ever read.

Re: ALPHA observes light spectrum of antimatter for first time

#53

Post by grkvlt »

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.

And also attached to different sides, not in a vertical row straight up the front of the creature, for instance... (When asked "What do you look for in a woman?" the Mathematician answers "Bilateral symmetry, of course!")

Re: ALPHA observes light spectrum of antimatter for first time

#54

Post by grkvlt »

Semiapies wrote: post #48
hossbeast wrote: post #15

Earlier quoted context omitted.

Many handed

But only bilaterally symmetrical. Radially symmetric aliens with hands give no indication! (Well, aside from whether or not they blow up whatever local matter surface they're standing on.)

That's neither necessary or sufficient! Notice that they could be bilaterally symmetric and two arms/hands positioned vertically on their front (anterior?) so no left/right hand distinction (but top/bottom instead) or; they could be asymmetric but have two hands/arms on one side, and one on the other, still giving them a left/right side choice.

Re: ALPHA observes light spectrum of antimatter for first time

#55

Post by grkvlt »

kirykl wrote: post #44
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)

Would antimatter interact with gravity opposite that of matter, prohibiting an alien (or anything) from being made of antimatter ?

No, it interacts identically.

This is a good question - so much so that there was an experiment[0] done at CERN before this one to find the answer. You are in good company asking this, despite downvotes!

[0] https://en.wikipedia.org/wiki/Gravitational_interaction_of_a...

Re: ALPHA observes light spectrum of antimatter for first time

#56

Post by grkvlt »

recycleme wrote: post #36
josho wrote: post #16

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

> I still thought antimatter was a theory. Your use of the word "theory" here seems to be a misnomer akin to the common statement "But X is just a theory."

Perhaps better to say "I thought [the creation of] antimatter was still theoretical." i.e. as opposed to practical?

Re: ALPHA observes light spectrum of antimatter for first time

#57

Post by 0xfaded »

IgorPartola wrote: post #43
HarryHirsch wrote: post #26

Earlier quoted context omitted.

I know, and the Lord Kelvin quote is too suspicious to be credible, a man like him would never have said such a thing. If we can trust Wikipedia he never did: https://en.wikiquote.org/wiki/William_Thomson#Misattributed

Didn't Isaac Newton die thinking that he solved all of physics though?

Newton was the first to experiment with light reflectance of glass of various thicknesses. He found the relationship but had no idea how a light corpuscule could know the thickness of the glass when it decided to reflect or not. Newton published his corpuscular theory of light but I certainly don't think he would have claimed to know what was going on.

Re: ALPHA observes light spectrum of antimatter for first time

#58

Post by euyyn »

bmh100 wrote: post #40

In case anyone is wondering about what antimatter actually is, antimatter is basically like normal matter, but the electrical charges are reverse. Take hydrogen for example. It is a massive, positive particle (the proton), orbited by a light, negative particle (the electron). Anti-hydrogen is a massive, negative particle (the antiproton) orbited by a light, positive particle (the positron) [1]. Why do matter and anti…

"Falling into the nucleus", as stated in that Stack Exchange question, is a classical (as in "wrong" :) ) way to look at it.

The 1s orbital of the electron is spherically symmetric, with non-zero probability of the electron being right in the center of the atom (so within the nucleus), and decreasing probability of it being farther away. So e.g. a good approximation of the He atom is of two neutrons, two protons, and two electrons, all in exactly the same position (with the electrons having "more spread").

At the end of the day, there are interactions that are seen in Nature and interactions that aren't. We codify the patterns as conservation of lepton number, baryon number, etc. If the numbers of what you have add up to zero, they can annihilate.

These conservation laws also accommodate other weird things, like beta decay, in which a neutron decays ("splitting") into a proton, an electron, and an anti-neutrino. It's not that the neutron is "composed" of those three things. But its total energy is higher than the sum of the energy at rest of those three particles: Whenever that's the case and the conservation laws allow it, we see it happen naturally.

Re: ALPHA observes light spectrum of antimatter for first time

#59

Post by bmh100 »

nonbel wrote: post #25
komali2 wrote: post #21

Earlier quoted context omitted.

It is a theory, like everything else in physics, including the workings of gravity. It's a bit of a shame that in elementary school and high school, people are taught about "facts" such as Newtonian physics without exploring also some of the weirdness of quantum physics that challenges classic physics. I.e. I had no idea about all the controversy around how gravity "actually" works until I read a book on string theor…

>"I had no idea about all the controversy around how gravity "actually" works until I read a book on string theory" FYI, there seems to be quite a bit of controversy regarding whether string theory is even science: >'Many of today’s theorists — chief among them the proponents of string theory and the multiverse hypothesis — appear convinced of their ideas on the grounds that they are beautiful or logically compelling…

I think it is important to keep in mind that theories can sometimes only become testable after sometimes unforeseen advances in technology. Consider the Higgs field, theorized in 1964 [1]. This field was only detected, via the Higgs boson, in 2012 [2]. The Large Hadron Collider (LHC) [3] and its computing grid, which detected the Higgs boson, generated 25 PB of data per year, had 150 PB storage, and 200,000 processing cores [4] (which I assume were at least 1 GHz on average). In the 1960s, the Cray CDC 7600 supercomputer had a computing speed of 36.4 MHz and 65 kword memory [5], and IBM produced the 1311 HDD with about 12 MB storage [6]. Thus, the LHC required advances in fiber optic cables, a 5-million-times increase in computing over existing state-of-the-art processors, an 89-million-times increase in computer storage (from 12 MB to assuming 1 TB per HDD), and integrated-circuit RAM. More directly, the 1971 ISR hadron collider had energies of 31.5 GeV [7] compared to the LHC's 6.5 TeV [8], 200x increase.

What other theories might become testable if we could reach 130 TeV, analyzed by a computing grid with 1 trillion processors and 1 yottabyte of storage?

[1]: https://en.wikipedia.org/wiki/1964_PRL_symmetry_breaking_pap...

[2]: http://www.smithsonianmag.com/science-nature/how-the-higgs-b...

[3]: https://en.wikipedia.org/wiki/Large_Hadron_Collider

[4]: https://en.wikipedia.org/wiki/Worldwide_LHC_Computing_Grid

[5]: https://en.wikipedia.org/wiki/CDC_7600

[6]: https://en.wikipedia.org/wiki/History_of_IBM_magnetic_disk_d...

[7]: https://en.wikipedia.org/wiki/Intersecting_Storage_Rings

[8]: https://en.wikipedia.org/wiki/Large_Hadron_Collider

Re: ALPHA observes light spectrum of antimatter for first time

#60

Post by tbabb »

jessriedel wrote: post #14
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…

> combination of parity and antimatter conjugation is a symmetry of the universe It's only an approximate symmetry. Look up CP symmetry violations.

CPT still holds, though, right?
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