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ATLAS sees first direct evidence of light-by-light scattering at high energy

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Re: ATLAS sees first direct evidence of light-by-light scattering at high energy

#61

Post by AnimalMuppet »

renox wrote: post #39
yohann305 wrote: post #25

Anyone else here is having a hard time seeing what could be applied usage of light-by-light scattering? (ie new computers? new internet? new telescopes?) Can someone here give us some insights?

Finding new particles: https://arstechnica.com/science/2017/08/researchers-may-have...

"Finding" may be too strong. The thing is, the photons scatter more often if there are more kinds of charged particles that could be created. The photons seem to scatter more often than would be predicted from the charged particles we already know about. That doesn't say anything at all about what the unknown charged particles are. But it may tell us how many unknown charged particles there are, which is just amazing.

Re: ATLAS sees first direct evidence of light-by-light scattering at high energy

#62

Post by cr0sh »

anfractuosity wrote: post #52
raverbashing wrote: post #12

Just as a reminder, those photons are high energy ones (Gamma-ray range) so no light sabers, holograms or anything involving visible light I am afraid

Electrolasers kind of seem slightly light saber-esque. I'm assuming miniaturisation of them would be tricky though, as i'm assuming ionization with a laser requires a lot of power.

I was about to make a comment regarding using UV lasers and ionization - then decided to take a second to google it, and found this interesting (though short) discussion:

https://www.physicsforums.com/threads/laser-to-ionize-air-to...

In short, I think your conclusion is likely correct...

Re: ATLAS sees first direct evidence of light-by-light scattering at high energy

#63

Post by hinkley »

yread wrote: post #21
raverbashing wrote: post #18

Earlier quoted context omitted.

Just make sure you have some sunscreen on

> Just make sure you have some sunscreen on in the thickness equivalent to 1cm lead sheet for a gamma-ray-screen factor of 2

So NIST is telling me that's about 16cm of titanium. I suppose it would be easier to make yourself clothing out of full lotion bottles than try to slather that much on.

Re: ATLAS sees first direct evidence of light-by-light scattering at high energy

#64

Post by hinkley »

mitchty wrote: post #51
soVeryTired wrote: post #31

Earlier quoted context omitted.

I've heard people make the argument about GR being essential to the GPS system before, but the skeptic in me has doubts. I don't deny that it's useful to have a correction derived from relativity, but is it really as essential as people make it out to be? If we hadn't known about GR when we built the GPS system, wouldn't we have realised there was an unexpected drift in the clocks and found a way to recalibrate them…

Yes its essential. Because the satellites are moving at orbital velocity, their frame of time is ever so slightly different than ours. To keep accuracy timewise without special and general relativity would be difficult if not impossible without understanding relativity generally. Could we have done GPS without relativity? Maybe, but we'd have to discover it with the satellites to be able to use it. A quick note from:…

I think I see what he's saying. Those satellites are moving at a fixed velocity. So the time dialation effect on them relative to the ground should be static.

It could reasonably be the case that we just adjusted the clocks on the satellites by .05% or whatever the drift rate is by measuring them against known points until we get it right. Good enough engineering.

Eventually someone would have asked some scientists to explain why it's happening.

Re: ATLAS sees first direct evidence of light-by-light scattering at high energy

#65

Post by ajross »

rrmm wrote: post #2

Neat-o. A little bit more info at https://en.wikipedia.org/wiki/Two-photon_physics . Basically two photons with enough energy to interact via virtual pairs created. It will be interesting to see the cross-section rates and maybe hopefully some new physics (as the wikipedia page weakly hints).

Yeah. The article is a little confused with terminology. Photon/photon interaction is "illegal" in QED in the same way and for the same reasons that wave solutions to classical electromagnetism don't interact (well, except to propagate). What's happening here are interactions between the two photons and the vacuum.

So the new science here isn't unexpected confirmation of new physics, it's our ability to probe our existing understanding of the vacuum with new interactions.

Re: ATLAS sees first direct evidence of light-by-light scattering at high energy

#66

Post by hinkley »

jerf wrote: post #54
Newtopian wrote: post #45

Earlier quoted context omitted.

Given the choice between trial and error engineering and science backed engineering I much prefer the latter. That does not mean doing engineering without the science is impossible just so much harder. They both go hand in hand, nothing mythological here. Advancements in one leads to ideas in the other and vice-versa.

"Given the choice between trial and error engineering and science backed engineering I much prefer the latter." That's not the question; the question is, are we forced to give up engineering if we don't have "the science" yet? And the answer is an objective "no", from abundant past human history. There's this myth sold that science always precedes engineering that is very, very popular. I'm not even sure where it's c…

We just overbuild until we have the science and the manufacturing capacity to back it up. Every once in a while I hear some civil engineering fan comment about how the roman aqueducts are still standing because they built a huge margin of safety into them (because they couldn't do the calculations, not because they wanted them to last a thousand years)

Re: ATLAS sees first direct evidence of light-by-light scattering at high energy

#67

Post by Florin_Andrei »

phkahler wrote: post #49
rrmm wrote: post #2

Neat-o. A little bit more info at https://en.wikipedia.org/wiki/Two-photon_physics . Basically two photons with enough energy to interact via virtual pairs created. It will be interesting to see the cross-section rates and maybe hopefully some new physics (as the wikipedia page weakly hints).

>> Basically two photons with enough energy to interact via virtual pairs created. Or could it be that a photon bends space-time as though it had mass, and they simply follow the local curvature and it looks like scattering? Just speculating, because for some purposes photons act like a solid particle with their energy equivalent mass traveling at speed c.

For that to happen, the energy-equivalent of the photons would have to be close to the Planck mass. That's an unbelievably high value for photons. We're not going to see that reproduced experimentally any time soon.

Re: ATLAS sees first direct evidence of light-by-light scattering at high energy

#68

Post by [deleted] »

nimish wrote: post #20
staticelf wrote: post #14

Can someone explain this in easier terms for a layman like myself?

Photons carry no charge, so normally they don't interact with each other. However, at high enough energies they do. The explanation given by the best available theory is that there is enough energy that a virtual electron and virtual anti-electron form, and since those have charges, they interact, and from the outside it appears that the photons interacted. This is totally impossible in the classical view, but is fin…

[deleted]

Re: ATLAS sees first direct evidence of light-by-light scattering at high energy

#69

Post by Coincoin »

chi17 wrote: post #9
etatoby wrote: post #7

One step closer to holograms.

Could you explain? Also, do you not think that current implementations that use eye tracking are not real holograms? What's to say that holograms similar to those of Star Wars could not be produced by inspecting the environment and automatically determining where people's head and eyes are, e.g. via a combination of technologies similar to the following: Eye-tracking holographic table requiring 3D glasses: http://www…

A real hologram, like in your last link, make the photons actually come from the correct angles so that everything is not in focus in your eye.

Stereo imaging we see in current VR and TV technologies do not simulate that effect, which makes it hard for some people to use as everything is focused at infinity or on the screen. What the lens (in your eye) is currently focused on is a very important depth cue for our brain and the conflicting information coming from the lens and stereo vision make some people unable to use stereo imaging or cause eye pain and headaches.

Unfortunately, real holograms are currently restricted to static images meticulously constructed using very advanced equipment that produces seemingly random images on films that interfere with each other to produce the hologram. Doing the same thing with moving images in real time would require too much computing power to currently be possible.

Another way could be to track the lens refraction properties and the pupil size in real time and fake some depth of field on the projected stereo images.

Re: ATLAS sees first direct evidence of light-by-light scattering at high energy

#70

Post by carapace »

soVeryTired wrote: post #31
ekimekim wrote: post #29

Earlier quoted context omitted.

Currently, very little. According to the article, you need crazy particle-accelerator-levels of energy to have them happen at all. However, by studying and understanding such events, we can test and improve our theories of physics, which may lead to breakthroughs in technology we can only dream of. For example, general relativity would have been considered completely useless knowledge for any practical purpose when i…

I've heard people make the argument about GR being essential to the GPS system before, but the skeptic in me has doubts. I don't deny that it's useful to have a correction derived from relativity, but is it really as essential as people make it out to be? If we hadn't known about GR when we built the GPS system, wouldn't we have realised there was an unexpected drift in the clocks and found a way to recalibrate them…

> an unexpected drift in the clocks

In every kind of clock.

I would hope in this scenario that that would have been noticed and it would have aroused sufficient curiosity to investigate and eventually discover that the effect was due to time itself flowing at a different rate.

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