Slashdot Mirror
Lasers Approach Their Ultimate Intensity Limit
Flash Modin writes "Death Star style superlasers? Don't bet on it. High-power lasers currently in development appear to be nearing the theoretical laser intensity limit, according to new research set to be published in the journal Physical Review Letters. Ultra-high-energy laser fields can actually convert their light into matter as shown in the late '90s at the Stanford Linear Accelerator (SLAC). This process creates an 'avalanche-like electromagnetic cascade' (also known as sparking the vacuum) capable of destroying a laser field. Physicists thought it might be a problem for lasers eventually, but this work indicates the technology is much closer to its limit than researchers believed. A preprint is available here."
Simply :(
Creating light from matter is rather ordinary in terms of physics, as can be seen in nuclear explosions
Or even running out of lighter fluid.
The SLAC experiment was just a singular event, but as lasers reach higher intensities the electric fields produced will increase as well and the team says that when they reach a critical intensity a cascade effect will occur as a result. The electron-positron pair is accelerated by the laser field itself at such high energies that they emit photons capable of spawning new pairs and continuing the process.
Maybe that's how the death star works? Besides, it isn't explicitly stated anywhere in the movies that the death star is a laser.
Also, they're not talking about a single laser, they're talking about colliding two laser beams.
Free Martian Whores!
Where are my sharks with laser beams then!?
Can anyone tell me why 99% of
Have they considered relabeling their laser intensity dials so they go up to 11?
We all know how avalanche-like electromagnetic cascades wind up.
"Death Star style superlasers? Don't bet on it."
Uh, you mean a bunch of laser beams that come out straight, stop for a fraction of a second, turn a few degrees and then join up and all go off in the same direction?
I wasn't exactly holding my breath for that, anyway!!
All this means is we need to be more imaginative with our designs. Limits are made to be broken.
Funny may not give karma, but +5 Informative never made anyone snort coffee out their nose.
We'll be fine as long as we pre-order a crate of red crowbars from Home Depot.
Sorry, this is new to me. What kind of matter is created? Full atoms? Just neutrons or protons? Or nothing more than subatomic bits?
A slashdotter who didn't build his own computer is like a Jedi who didn't build his own lightsaber.
Can convert light into matter?
Sooooo PewPewPew, eventually becomes SplatSplatSplat?
That's an interesting kind of awesome right there.
Is there a theoretical upper bound to the maximum efficiency of converting energy into coherent light (lasing), other than the obvious "nearly 100%"?
What is the most energy efficient laser in production today, and how close to the theoretical max will lasers get within the next 5-10 years?
--
make install -not war
Funny, I didn't read anything in the article about sharks.
Henchman: "Professor, I've increased the laser's power to a new incredible limit, and something remarkable has happened. It is creating new matter! I can tune the beam to create any matter in any configuration we need!"
Professor: "Darn. We needed a big laser. Oh well, throw it all out, that was a dead end."
- For the complete works of Shakespeare: cat
Isn't the fact the electron/positron pairs can be created in a vacuum by a strong enough electromagnetic field pretty interesting Physics in and of itself? What goes around comes around -- every day we get closer to resurrecting the theory of the luminiferous aether... (Yeah, I know... energy in a vacuum is not exactly the same thing.)
I've abandoned my search for truth; now I'm just looking for some useful delusions.
Every five or so years, someone comes forward and says that hard drives are nearing their physical limit. And then someone else makes a big breakthrough and continues the growth. Are we going to have to go through the same roller coaster ride with lasers too?
All right, consider "Create planet busting laser" to be scratched off my ToDo list. Now I've got to figure out what to do with that corner of my basement.
Suppose you were an idiot. And suppose you were a member of congress. But then I repeat myself. -- Mark Twain
Yes, we will need to move to Phasers and then Photon and Quantum torpedoes at some point.
Just because I can hook a shark from a boat, I do no offer to wrestle it in the water.
But it is energy that was stored in a either a chemical bond, or an electron state. Matter does not disappear, it is just electrons rearranging their orbits. If you count all the protons, neutrons and electrons before and after the chemical reaction, they're all still there.
Those who can, do. Those who can't, sue.
We need him to proclaim: "The intensity of lasers will double every two years" and everything will be fine.
right? what does one mean by "intensity"? is that simply amplitude? simply frequency? their product? if it's one or the other you can always increase the other. if it's both, then i guess you can just use a wider beam, but that means overall energy transfer rate per unit surface area is limited. well, coherent transfer, at least. anything beyond a certain threshold would diminish (exponentially) with distance. reminds me of the speed of light being constant or the "channel capacity" in information theory.
You're joking, right? About how "Ken Burns will revisit that period of the galactic history and we'll get a more neutral viewpoint of the conflict."
For "more neutral viewpoint", substitute:
"Ken sank his heart and soul into this thing, and it's obvious that he's still grieving for Alderaan."
Don't forget the soft, heart-felt banjo-centric soundtrack.
-kgj
Anything that requires 47 billion eV electrons and a 1 trillion watt laser has to be freaking amazing to be a part of.
Yay Science!
"I must not fear. Fear is the mind killer." -Bene Gesserit Litany Against Fear
>Anonymous Coward
>sharks
Apparently not.
#naabhaprzrag, #sverubfr-000, #agi-fcbafberq, negvpyr[pynff*=' negvpyr-ary-'] { qvfcynl: abar !vzcbegnag; }
If you count all the protons, neutrons and electrons before and after the chemical reaction, they're all still there.
But the mass is not.
Give me Classic Slashdot or give me death!
So we are approaching the intensity at which light turns into matter. One step (of many) to building a transporter?
Both nuclear and chemical reactions destroy matter, if you can call that destroying matter.
In a chemical reaction, electrons change states. In an exothermal chemical reaction, the energy of those electron states is lower than the energy of the electron states before the reaction, and energy is released in another form (photons, kinetic energy, etc.). If you count the neutrons, protons, and electrons, they're all still there. But mass has been lost, because the binding energy of the electrons counts in the mass of the molecule. (In the reaction, binding energy was lost and converted to another form. Energy is mass.) However, chemical binding energy is tiny compared to the energy in the rest mass of protons, neutrons, and electrons.
In a nuclear reaction (fission and fusion), the states of nucleons (neutrons and protons) also change. Again, if you count the neutrons, protons, and electrons, the same ones present before are present after. (Sometimes they change form, like n p + e.) But mass has been lost, because the binding energy between the nucleons counts in the mass of the atom. (In the reaction, binding energy was lost and converted to another form. Energy is mass.) Nuclear binding energy is still small compared to energy in rest mass, but it's a lot bigger than chemical binding energy.
That's because lighter fluid is boring, but nuclear fusion converts protons + electrons into neutrons, and the mass difference is given off as energy. So there is NOT the same number of protons electron and neutrons before and after.
Particles can indeed disappear, that's why it's hard to discover new particles, because they often live for much less than a nanosecond. They usually decay into other particles and gamma rays.
Think of what happens when a high energy cosmic ray hit the upper atmosphere, it creates a shower of particles.... that's what the laser beam will do at high enough intensities... this is because it's all in phase, and at high intensities, many photons are in the same quantum state... so it will act like a gamma ray, even though it's not at a high frequency.
"Don't Cross The Beams!!!!!"- Ghost Busters
*Ultra-high-energy laser fields can actually convert their light into matter as shown in the late '90s* If you can convert laser energy into matter then why not make a hamburger from the reconstituted matter stream :)http://www.youtube.com/watch?v=xHSD0tR2IOU
...what about PHASERS? What about other materials that get lased? Whenever I hear something about "we're reaching the end of [insert technology here]'s abilities" I always take it with a grain of salt. Sure, with current techniques and materials we are reaching the end of the power curve, but we're certainly not at the dead end for the technology. Or, maybe we are, but there will certainly be something that comes along to supplant it. It's not like oil where there is a finite supply of the stuff. How many times have we heard that hard drives could not possibly hold any more data?
If two or more sub-critical intensity lasers were fired at a single point at a distance, would the cascade of gamma-ray photons created in the collision be of significant destructive capacity to justify all this setup or would it just cause the lasers to disperse and fizzle out?
...before and after a nuclear reaction, I either get bored quickly or I grow senescent and die long before I get to 'after'.
True, but if you could actually measure the mass of the butane molecule with enough precision, you would find that it is more massive than the constituent atoms alone. This extra mass (m=E/c^2) is actually due to the potential energy stored in the bonds.
Boom-sticks.
From S-Mart.
Sounds like scientists didn't ever expect to see a cascade, let alone create one.
Immolation is the sincerest form of flattery.
They're building a 5 (five) Petawatt laser in Romania - Magurele, that's plenty enough for a deathstar.
Wouldn't passing the limit be a great way of making them?
What's scarier than physical matter moving at the speed of light? Isn't this a good thing if you were looking to create a Death Star?
It's obvious you stopped at 'Intro to Meme Physics'. Had you continued to P.H.D.[Piled Higher and Deeper] level 'Meme Physics', you would realise the synergy brought about by combining memes can be catastrophic.
For instance, should Spinal Tap attempt to jump a shark with lasers mounted on it's frikkin head while performing their new hit single: "That's No Moon!", the resulting debacle would surely go to '12' if tried in Soviet Russia, where shark jumps you!
*Disclaimer*
Don't try this at home kiddies, as an errant data point being overlooked could end the universe.
You think the 'Big Bang' was something? Ha! You ain't seen nuthin' like the sure to happen 'Big Suck' that would result as the internet[and all life as we know it] imploded!
*end Disclaimer*
No, the solution to this problem is obvious...invent bigger sharks, and mount a whole battery of frikkin' lasers on their heads. Simple, really.
Down With Slashdot BETA!!! I've been around the corner and seen the oliphant; you can only abuse me from your perspecti
Sure, the beam needs improbable energy but is the intensity limit actually a problem? Assuming you have the energy, wouldn't a wider beam (within the intensity limit) work as well?
Comment removed based on user account deletion
Chemical energy is energy and is matter too. If you measure 8 tons of oxygen and 2 tons of hydrogen (hopefully I got my stochiometry right), and let them react, and cool off, and measure the total weright afterward you will find it changed.
Mass energy equiavelence, scroll to "Binding energy and the "mass defect".
C. Sagan : A demon haunted world:
http://www.amazon.com/gp/product/0345409469/
visit randi.org
You save some money buying them in bulk like that but you are going to feel like an idiot trying to open the wooden crate of crowbars when you start hearing the chirping up in the air vents.
Account -> Discussions -> Disable Sigs
This places a limit on the peak intensity of a laser beam, not on the peak (or average) power. It does not limit the total energy per pulse nor the power output of a laser. Furthermore, the limit is far beyond the level that turns anything the beam hits into plasma. It has no relevance to laser weapons except insofar as the the effect may someday be utilized for destructive purposes. It may have some relevance to laser fusion.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
Mod parent up, please (I'd do it if I had mod points).
People talk about "transforming mass into energy" in nuclear reactions, but they almost never say that it's actually much more mundane than that. You don't need nuclear reactions (or even chemical reactions): a sinning top, for example, has more mass than one that's standing still. Here is a somewhat known physicist talking about that, if you don't want to believe a random person on Slashdot.
you guys are all virgins, right ?
Maybe, but we would probably need to discover some new physics.
Physically, hard drives could theoretically store some amount of data based on the smallest possible magnetic domains on the platter. We have had technical limits in reducing the area that each bit uses on the hard drive platter, but I doubt that we are particularly close to hitting the physical minimum size limit.
With these lasers, the amount of energy crammed into a unit of volume is getting so high that the photons are condensing into matter when they collide with the photons of another laser beam. A single beam, twice as intense would do the same thing, but without having to collide with anything. That would pretty much be the limit of intensity. Even long before that the beam would start to become unstable, as stray ambient photons would start to cause particle cascades in the beam.
As an aside... I wonder what would happen to the laser itself when the particle cascades start to occur. Electrons and positrons are produced, so presumably the positrons would collide with the hardware of the laser and start annihilating electrons. Seems like that would tend to cause the molecular bonds within the laser to be disrupted. Maybe the free electrons would fill the gaps just as quickly, preventing damage, but even if that is the case, there would still be a lot of heat generated, which can't be good.
Put simply, in deference to you, Kent, it's like lazing a stick of dynamite.
1. 2.
True, but if you could actually measure the mass of the butane molecule with enough precision, you would find that it is more massive than the constituent atoms alone. This extra mass (m=E/c^2) is actually due to the potential energy stored in the bonds.
Less, else it wouldn't be a bound state.
So that's what they've been planning...
And if you count all the subatomic particles before and after a nuclear reaction, they are all still there as well.
Well, for the main fission reactions, sure. But there are a lot of secondary reactions that will create and destroy nucleons and electrons.
As I understand it this article is about using lasers to gernate electron-positron pairs from the vacuum.
A short search in google scholar showed up a lot of papers about this, for example this one from the year 2000:
http://apl.aip.org/applab/v77/i17/p2662_s1?isAuthorized=no
Ultra-high-energy laser fields can actually convert their light into matter
So I have this idea that you could blast an object into (well) nothing with intersecting laser beams, transmit data on the resulting interference patterns, then reproduce the same interference patterns at another place with intersecting laser beams powerful enough to create matter.
Sounds like teleportation to me. Anybody want to give it a go? (you furst).
http://michaelsmith.id.au
True, but if you could actually measure the mass of the butane molecule with enough precision, you would find that it is more massive than the constituent atoms alone.
I don't think this is quite right. The butane is actually less massive than the constituent atoms. That is why it sticks together, and why you don't have a heap of hydrogen and carbon atoms flying around instead. In order to dissolve the bound butane molecule into free atoms, energy must be added; this is the binding energy.
However, if you could measure the mass of butane molecule and the oxygen molecule(s) it reacted with before and after the reaction, you will find that mass has decreased. This decrease corresponds to the energy released by the burning, with a conversion ratio given by m=E/c2.
Paddle faster, I hear banjos
But mass has been lost, because the binding energy between the nucleons counts in the mass of the atom. (In the reaction, binding energy was lost and converted to another form. Energy is mass.)
Only in the way that pouring water out of a cup counts as mass "lost". When you perform these experiments, you are just letting the mass escape your test bench, because, as you said, energy is mass (and vice versa).
[Your analysis is right, I just wanted to add an extra analogy for a reader who may get confused.]
>> Standing on head makes smile of frown, but rest of face also upside down.
After actually reading a bit more, well... These papers are about generating positron-electron pairs from the collision of two electron beams, with the electrons being accelerated by laser.
The long-known theoretical intensity needed for pair generation is 10^28 W/cm^2. From what I just found this has not been achieved yet. In the paper linked in the summary it is stated that a single pair generated will lead to the generation of a lot more pairs: The generated electrons and positrons are accelerated by the electric field of the laser beam, reaching energies high enough to emit more pairs.
This is about the intensity in a focussed laser beam. In the laser itself you will get problems at much lower intensities.
It still doesn't explain why the blaster beams usually fly with about the same speed as arrows(or bullets, if you are lucky)
This is just disastrous for Pink Floyd tribute bands worldwide.
Crap! Where's Gordon Freeman when you need him?
No, the solution to this problem is obvious...invent bigger sharks, and mount a whole battery of frikkin' lasers on their heads. Simple, really.
Just don't cross the beams!
Not true! In beta decay, a neutron decays into a proton, electron, and a neutrino. Three particles from one. Neutrinos are also produced in fusion -- the sun splits them out in huge numbers. Even light bulbs turn energy into photons. New particles are created all the time, even without antimatter.
What a fool believes, he sees, no wise man has the power to reason away.
So, "sparking the vacuum" will become the new "nuking the fridge"?
Avalanche-like electromagnetic cascade of High intensity lasers? I'll be right back, i just need to go to the hardware store and acquire a crowbar.
a few years from now when they figure out a neat trick to sidestep the problem.
Seriously, we need to stop saying 'it won't happen' and 'it can't be done' because that just means the guy talking isn't capable of doing it and someone else is going to figure it out in a few years anyway. Probably some kid who got bored and realized the 'laws' his teacher was feeding him weren't nearly as clear nore carved in stone like they are made out to be.
The won't create a super powerful laser doing it the way these guys did ... someone else using an entirely different method probably will eventually.
Their lasers won't ever be super powerful death rays like Star Wars ... someone elses might be though.
Funny thing about physics, the people who REALLY know what they are talking about also know that the more we learn, the more we realize how little we actually know. The ones who REALLY know physics don't talk in absolutes because there are no absolutes.
Persistent Volume manager for Kubernetes - https://github.com/dwimsey/openshift-pvmanager
The researchers at the SLAC need to recheck their results, because Andy Schlafly, Conservapedia founder and a Eagle Forum "University" instructor has noted that E=mc^2 is a liberal plot.
Yet more experimental evidence that reality has a "liberal" bias.
Luke, help me take this mask off
No, neither nuclear nor chemical reactions destroy matter, it simply changes forms. Instead your measuring potential energy and calling it mass because your measuring instruments can't tell the difference.
Persistent Volume manager for Kubernetes - https://github.com/dwimsey/openshift-pvmanager
For future reference, the instant you make it about a 'political team' then you've pretty much show how ignorant and out of touch with the world you are, especially when it comes to politics.
If you have to use the word 'liberal' or 'conservative' to proof your point, you don't have a point to proof, just stupidity and ignorance to spew.
Persistent Volume manager for Kubernetes - https://github.com/dwimsey/openshift-pvmanager
No, in chemical reactions there is NO change in mass.
Well played, rts008, well played indeed. (:
"There is a way that seems right to a man, but its end is the way of death." Proverbs 16:25 (NKJV)
For future reference, attempt to "get" the punchline.
Luke, help me take this mask off
I thought it was conservatives who are ignorant and out of touch with the world. They astound me every day with how much so!
What a fool believes, he sees, no wise man has the power to reason away.
"Matter does not disappear,"
Well, basic ELEMENTS do disappear. This is what we call a half-life, yes? Eventually entropy demands that substance be destroyed because not enough energy exists to maintain the state, right?
Still waiting on Serviscope_minor to wake up to fucking reality and realize that Jessica Price isn't going to fuck him.
No, you are wrong. There is a change in mass due to the change in bond energies, which is completely analogous to the energy released in nuclear reactions, only the magnitude is of course far smaller.
Of course this mass difference is far too small to be observed in everyday situations, but the rule you are quoting is a high-school chemistry approximation, not the full reality.
Physists diagree about that. After all the mass of the neutron exceeds the mass of the proton and electron and the antineutrino. One could say the mass that disappears is merely potential energy being registered as mass, but physicists do not do that.
Physicists see only a vector of mass-energy whose magnitude is the same in all inertial reference frames, but the angle can differ. In any given reference frame in all reactions the sum of all mass-energy vectors in the system is conserved.
Let us remember what that vector looks like. E^2=(mc^2)+(pc)^2 is how we calculate the magnitude of the mass-energy vector. So the two components are the energy of the rest-mass and the energy of momentum.
Now how do we account for the fundamental forces? Let us consider one of them. Let us consider the electro-magnetic force, and two particles of opposite charge. At first they are at rest in this reference frame. But then they move towards each other. Since they started moving they both now have momentum. But that momentum means they now have a momentum component to the mass-energy vector.
But if they kept their original rest mass then the additional momentum means that both now have larger mass-energy vectors. But they are the only two particles in our imaginary closed system, so there are no other mass-energy vectors whose magnitudes could have decreased to compensate. The only way to conserve mass-energy is for the rest mass to have decreased.
Therefore the rest-mass in this reference frame must be accounting for any potential energy caused by the fundamental forces.
Stylish sheet to fix many problems in Slashdot's D3: https://gist.github.com/801524
I don't mind you not knowing.
Being wrong when asked is worse, but not so bad.
Going out of your way to post something wrong is unacceptable.
Know what you know and stay silent about the rest.
Aw come on, everybody knows that Hiroshima and Nagasaki were just figments of the liberal media.
thegodmovie.com - watch it
Heh. I meant a spinning top, of course :)
Made me laugh!
-kgj
You're measuring energy and calling it mass because they're the same. Always, when you measure mass, you're actually measuring energy in many forms at once.
Who the hell modded this up?
Talk about being astounded.
I was about to post a counter argument, but on second thought I think you're right. I was previously thinking that the butane molecule was sitting at a local minimum in energy, and that it would actually release energy if disassociated. I realize now that it is at an absolute minimum, but that minimum is not as low as the minimum available in the form of CO2 and H20, thus the exothermic reaction with O2.
So basically, you are absolutely correct.