
Scientists propose collider that could turn light into matter - jonbaer
http://www.theverge.com/2014/5/18/5724658/photon-collider-could-turn-light-into-matter
======
jobu
Did anyone else think Star Trek replicator when they saw this headline?
[http://en.wikipedia.org/wiki/Replicator_(Star_Trek)](http://en.wikipedia.org/wiki/Replicator_\(Star_Trek\))

We're definitely a long way from "Tea, Earl Grey, Hot", but it's cool to see
people looking into these sorts of things.

~~~
swalsh
Your power bill would go through the roof though.

------
InclinedPlane
This is just an interesting experiment, nothing more. It's already well
established that high energy photons can create matter/anti-matter particle
pairs, it's done all the time in the laboratory in a variety of conditions.
However, there are some subtleties behind the process. A single photon in
empty space won't necessarily spontaneously cause pair-production, you need a
suitable environment for it to happen in. Typically this happens within
matter, when high energy gamma rays travel through a physical material. And,
indeed, this is an important process in stellar stability for extremely high
mass stars. When extremely massive stars (130 to 250 solar masses) get old
enough their cores heat up to such high temperatures that the glow from the
hot matter includes photons with energies high enough to cause pair
production. When enough of the thermal energy of the star's core gets dumped
into photons of such energies the star becomes unstable, because the photon
pressure is reduced due to the production of electrons and positrons (which
re-annihilate and produce photons again, but there's a time gap). The
instability results in a supernova/hypernova/gamma-ray-burst.

Anyway, in theory high energy photons should be able to cause pair-production
even without interacting with matter, such as merely interacting with other
photons. And that's what this experiment is designed to test.

~~~
jessriedel
> It's already well established that high energy photons can create
> matter/anti-matter particle pairs, it's done all the time in the laboratory
> in a variety of conditions.

Well yes, but the important thing here is that _free_ (i.e. on-shell) photons
are being collided with each other to create matter. (Think of one laser
pointed at another laser.) This has been done before, but only relatively
recently and certainly not routinely. Here's one place:

[http://www.desy.de/~telnov/ggtesla/](http://www.desy.de/~telnov/ggtesla/)

------
asafira
Has anyone been able to find a link to the original paper? The link on The
Verge is broken, and I couldn't quite find it with a quick google search.

~~~
jds375
Apparently the embargo for this paper has not yet been lifted. It says: "Once
embargo has lifted, the paper can be downloaded at :
[http://dx.doi.org/10.1038/nphoton.2014.95](http://dx.doi.org/10.1038/nphoton.2014.95)
"[1]

[1] [http://www.eurekalert.org/pub_releases/2014-05/icl-
sdh051514...](http://www.eurekalert.org/pub_releases/2014-05/icl-
sdh051514.php)

------
stephengillie
_When the photons collide, the researchers believe that a significant number
of them will turn from light to matter — more specifically, into an electron
and a positron._

So we could use this within our warp core to power our warp field generators?

How much energy would we have to expend to separate the positron from the
electron and keep them separated? What does that give us in terms of energy
storage efficiency, compared to storing electrical charge within a lithium
battery?

~~~
kachnuv_ocasek
Extremely infeasible.

~~~
stephengillie
That's an extremely pessimistic reaction! I think such a device will at least
be possible, and that we'll eventually engineer the energy density of it down
to be comparably efficient.

And we've got to power the warp field with _some_ thing, so what are our most
energy-dense options?

~~~
darkmighty
Storing antimatter is an engineering nightmare. It's hard enough to store
chemicals that react with lots of things, imagine storing something which
reacts releasing _insane_ energies with _all matter_. You have to confine it
perfectly using external fields. In other words, not an easy task. (CERN has a
trap that was demonstrated to have formed just a few antihydrogen atoms)

Not that we have any applications for it with the current production
efficiency.

~~~
jessriedel
To my understanding, this isn't correct. Storing anti-matter isn't really that
hard. The Tevatron would store anti-protons in the recycler for hours, and I'm
sure if it was important we could engineer much more efficient mechanisms.

No, the hard part is creating the anti-matter in the first place and then
cooling it down to a reasonable temperature at which it can be stored. All of
our mechanisms for creating anti-matter generate anti-particles traveling at
fantastic, highly relativistic speeds (and also consume much, much more energy
to create then they contain in mass energy). Cooling them down without loosing
them all to annihilation is very difficult. But once they're cool, it's not so
bad.

~~~
darkmighty
Oh I'm sure you're right, didn't know that (my knowledge comes from years of
exaggerated Scientific American articles :) ).

I suppose the cooling is electromagnetic, the whole process must be really
difficult! Cool it while keeping those atoms from interacting from stray
particles if the vacuum isn't perfect.

------
justintocci
i'm confused. why do you need to accelerate electrons? wouldn't a Van De
Graaff accelerate electrons to a high rate of speed?

~~~
al2o3cr
Van de Graff generators are certainly useful for the first 20 MeV or so, but
the source photons generated by the electron beam in this case are >500 MeV.

------
wcoenen
I'm sure that physicists already have plenty of evidence that matter can be
created from energy. So I wonder what they hope to discover by doing this?

~~~
secretdark
We have plenty of evidence the rest of the solar system exists. Why bother
exploring it?

~~~
im3w1l
Because earth is overpopulated and we will have to settle new worlds. Because
sooner or later earth will go FUBAR, and it'd be nice if not ALL humanity
dies. Because it's safer if we find the Aliens before they find us.

~~~
smtddr
You think that's the only, or even main, reason we explore the universe?

What if we do it because it's in our nature to explore? Just pure curiosity?
To increase our understanding of existence and evolve into something more?
Also, this concept of it's safer to find aliens before they find us sounds
like you're already of the mindset of war and you want a tactical advantage
over something that you've never seen or know anything about. I really hope
not everyone thinks of exploring the universe as just another military mapping
of strategic attack/defense positions. If the human race is still being driven
by fear and war when star-trek-style travel becomes possible, then maybe it's
better we just die right here rather than export our madness throughout the
galaxy.

~~~
BugBrother
Uhh... I voted you up for the first part.

The second part was simply naive. Please consider game theory.

Yours (and mine) moral is from a society with a functioning police force, rule
of law and state violence monopoly. Without that, there is a clan society,
where your only security is that others (generally relatives) will revenge
you. A form of terror balance. Out moral just doesn't work there, since to
avoid violence _you_ have to make people believe you are ready to inflict it.

(I am unaware of a third alternative to state violence monopoly and clan
societies. There are obviously places in between, with organized crime (south
Italy, Mexico?). Please educate me if I miss something basic?)

Let me take an example:

There is no world police since Obama seems to be abdicating USA's partial
role, countries now live in an analogue of a clan society (e.g. do alliances
for protection from aggression).

Consider how Russia and China are starting the jingoism garbage again. How do
you know other countries/species won't?

tl;dr: Don't take your moral instinct for logic.

~~~
smtddr
_> >since to avoid violence you have to make people believe you are ready to
inflict it._

So basically...
[http://en.wikipedia.org/wiki/The_Butter_Battle_Book](http://en.wikipedia.org/wiki/The_Butter_Battle_Book)

If this is truly all the human race is capable of; living in a perpetual
stalemate of attack-power then we should just stay on our earth and perish.

~~~
BugBrother
I assume you're trolling, but will waste a few more minutes:

Game theory is used for evolution too, so you're a creationist?

A longer answer would be along the lines of:

Humans have a wide range of possible behaviours, the trick is to organize
society so we get a "nice" place (i.e. it is not "paying" to be non-"nice",
please note quotes for complex PhD thesis definitions). If you're not able to
see the world, your decision will have harmful effects according to your own
morals. In short, your absolute moral judgements is a problem as much as
Putin...

(I just wish that there were some way of educating away moral condemnation of
people which refuse to understand stuff which goes against their ideology.)

Knowing idealists, in some generations people like you will want to
genetically modify people to follow your morals -- Socialist "new human"
style. We know how that goes, not only from science fiction.

But I already wrote an answer and got a non sequitur.

