Scientists discover how to turn light into matter after 80-year quest (2014) | Hacker News Reader

Scientists discover how to turn light into matter after 80-year quest (2014)

phys.org

This is from 2014 and proposes the experiment. Follow ups have been interesting, here is one from 2017 (https://www.nature.com/articles/s41598-017-17605-6) which actually generates positrons.

And here is the discussion from 9 months ago: https://news.ycombinator.com/item?id=15725759

Damn, I hate it when they confuse theory, modeling and experimentation! In the cited discussion, splittingTimes noted:

> Since 2014 I can find 34 citations, none of which are an actual experimental realization of their scheme [1]. ...

So has that changed? Or is this just theory and modeling?

Sadly it hasn't changed as far as I can tell. The nature paper cited helps summarize some of the approaches being considered.

My lord, who wrote this article?

Imperial College London physicists have discovered how to create matter from light - a feat thought impossible when the idea was first theorised 80 years ago.

They didn’t discover it, as they say in the same sentence this is an 80 year old theory, rather they demonstrated it in a lab rather than observing it in nature. That sentence also makes it sound like this process may have been considered impossible until they demonstrated it in the lab, and that is just not true.

Plus this stupid site clipboard hijaacks. Feh.

The article implies that they "demonstrated it in a lab". But actually, they just imagined a way to do that. And as far as I can tell, it hasn't yet been tested.

How is it that some physicists seem to talk about results of modeling as if they were experimental results?

Photon-photon scattering has been observed: https://en.wikipedia.org/wiki/Two-photon_physics

OK, but that's not Breit and Wheeler "photon-> <-photon" to "<-electron positron->", right?

That's quite neat! Maybe important to note that they have described an experiment to test the theory but not conducted an experiment yet. :)

For reference it looks like the uniqueness here is they are using lasers (photons) for electron-positron pair production.

Particle colliders like LHC and it's progenitors all create matter as a fundamental part of their operation, but I guess they're classifying that as "energy" to matter not "light" to matter.

Matter to matter, actually. LHC shoots protons and antiprotons at each other, also it can shoot heavy nuclei and anti-nuclei at each other. Other types of colliders can also use electrons and positrons.

https://home.cern/about/updates/2018/07/lhc-accelerates-its-...

The uniqueness isn't just that they are using lasers (that's been done) but that they are using only lasers. There are many different ways you can get pair production from high energy photons, one of the easiest is via an interaction with a charged massive particle (such as an electron, proton, or atomic nucleus). But it's also possible for pair production to be a purely photon only process (just as the reverse process of annihilation producing only photons is possible), however that is a lot more difficult to pull off experimentally.

The experiment described here was performed by a couple of groups independently earlier this year. Data is being analysed, so fingers crossed!

Really! Can you share any specifics, cites, etc?

1) Create plausible way to confirm 80 year theory

2) Say that the only way to test requires "slabs of gold"

3) Profit?

It worked for the alchemists!

Seems, from reading, they see actually turning matger and light into matter. Multiple lasers, yes, but there looks like matter being consumed in the process.

In my reading, there would be thermal radiation (aka light) and a high intensity photon beam (aka light) interacting to create particles.

I didn't see matter being consumed anywhere, did I miss it?

Actually, it seems that they are doing nothing. They're talking about it, but there have apparently been no experimental confirmations.

Using a couple of lasers to create matter makes a whole bunch of weird things possible. And while we're dreaming, this would be one heck of a 3D printer, provided you'd be willing to wait a literal eternity for your device or product!

Anyway, obviously that's still science fiction but this at least opens the door.

Here's something even crazier: Are photons in vacuum, with photon-photon scattering, IN PRINCIPLE a model with strong enough computational power? I don't have any specific application in mind, but just for the kicks, how cool would it be to create a galaxy-sized computer that has no parts other than photons? I don't mean "no _moving_ parts other than photons", I literally mean a photonic computer where even the reflectors are made of other photons.

Someone beat you to that idea by about 8.9 billion years.

Relevant Wikipedia article: https://en.wikipedia.org/wiki/Breit%E2%80%93Wheeler_process

Would this be able to be used as a fuelless space propulsion method?

Yes, but it's SO impractical as to be unusable (remeber, that E=mc^2, so m=E/c^2, which means m is REALLY small).

Edit: You will get very small amounts of matter from energy. Small amounts of matter will mean very low thrust. Much better use of that amounts of energy is just collecting interstellar medium and accelerating it.

it is worse than impractical actually light is the best propulsion method per energy consumed (as propulsion efficiency depends on speed) it is just that to expel a given mass of light you also need a huge dead weight to emit it.

it would be way more useful to have a method to turn matter into light. this would be a fantastic low power space engine.

(not really an expert, but pretty sure about this)

Well, to turn matter into light is basically the same as turning matter into energy.. which will, of course, produce a lot of it: E=mc^2

That's really hard though, unless you use antimatter+matter. And then you'll have to produce the antimatter first, of course. And you're back to square one.

> And you're back to square one.

Well, not necessarily; if you could efficiently produce and store antimatter, that'd make a hell of an energy storage mechanism, and possibly make interstellar travel feasible. That's a HUGE if, obviously.

That right there is a fuel with a Roland Emmerich scale for potential (nuclear) fallout. Can you imagine trying to sell that to the public? "Combine the worst parts of both Challenger and Chernobyl." The public doesn't really accept normal nuclear power plants.

Don't do it on earth, do it somewhere else in the solar system.

Sure, if you're ready to build your spaceship inside the sun.

This is from 2014.

Completely missef that. Should probably be added to the title.

Thanks! Added.

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