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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!!
We'll be fine as long as we pre-order a crate of red crowbars from Home Depot.
Limits are made to be broken.
The opposite of this is true.
Can convert light into matter?
Sooooo PewPewPew, eventually becomes SplatSplatSplat?
That's an interesting kind of awesome right there.
Well gee, if only there were a link to an article about it.
In a report published this month by the journal Physical Review Letters, 20 physicists from four research institutions disclosed that they had created two tiny specks of matter -- an electron and its antimatter counterpart, a positron -- by colliding two ultrapowerful beams of radiation.
As for this being new...
The possibility of doing something like this was suggested in 1934 by two American physicists, Dr. Gregory Breit and Dr. John A. Wheeler.
Energy converts to matter, and matter to energy, all the time. Check out Feynman diagrams for many examples. Particle colliders are machines built for the purpose of converting energy into matter. When particles collide, some of their energy converts to various forms of matter.
What a fool believes, he sees, no wise man has the power to reason away.
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
Everything that can be invented has been invented.
The telephone has too many shortcomings to be seriously considered as a means of communication.
640k ought to be enough for anybody.
Turns out nobody can ever predict the future of technology (except maybe Orwell, but no one wants to admit that).
Just because we can't think of any way to break this "theoretical limit" doesn't mean it can't be broken. I'm sure at one time they said it was impossible to go faster than sound.
Funny may not give karma, but +5 Informative never made anyone snort coffee out their nose.
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.
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.
Its been suggested some planes in WWII, in dives, were actually breaking/transitioning the sound barrier. This is why many planes never pulled out of their dive and crashed into the ground. The reason being, not enough control surface to function with the shock waves (compressibility) to allow for maneuvering to avoid their fate. This was, in fact, a fate repeated by many test pilots who attempted to break the sound barrier. It wasn't until the flying control surface was created that the problem was licked.
This is a common misconception. No, the particles that result from collisions were not already there. The top quark was created from a collisions of particles that did not contain a top quark. The same is true of bottom quarks, strange quarks, and charm quarks. The particles come from the energy of the colliding particles. That's why the energy of the collisions determines the maximum amount of mass of the particles the collider can create.
Just think about it for a few seconds. If new particles could not result, how can we make new types of quarks and antimatter? When we collide electrons and positrons, how could other types of particles possibly result?
What a fool believes, he sees, no wise man has the power to reason away.
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.
Einstein disagrees with you. He says that energy and matter and interconvert, according to E=mc^2. This is exactly how particle colliders work. The LHC pumps lots of energy into hadrons and smashes them together, converting some of the energy into many different particles. We hope to be able to see Higgs bosons that are created in this way. Because they are proposed to be massive particles, lots of energy is needed to create them.
What a fool believes, he sees, no wise man has the power to reason away.
No no no. Broken are made to be limits.
Also, Limits are broken to be made
Unfortunately, that opening paragraph is horribly written. The rest of the entry is better, and gives an accurate though terse description of the problem. Before the 1940s, many aeronautical engineers believed -- quite rightly, givem the technology of the day -- that they couldn't design a plane that would hold together while passing Mach 1. Nobody ever claimed that it was physically impossible to fly faster than sound, and of course such a claim would have been absurd given that there were plenty of examples of things that did just that (e.g. bullets.) Serious attempts to build a supersonic airplane began in the 1930s, and by the start of WW2 everyone working in the high-performance aircraft field knew it was possible, they just didn't know exactly how to do it.
In short, it was an engineering problem, not a scientific one. This is completely different from limitations which are founded, as far as we can tell, not in the state of technology but in the laws of nature.
If out current understanding of the limiting natural laws turns out to be wrong, great -- I'd love to see a Death Star just as much as any nerd would. But don't bet on it. The fact that the X-1 flew no more means that we'll someday have faster-than-light starships with planet-destroying laser weapons than the existence of the internal combustion engine implies that perpetual motion machines are right around the corner.
The correlation between ignorance of statistics and using "correlation is not causation" as an argument is close to 1.
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".
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visit randi.org
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.
What E=mc^2 actually means is that energy includes a term involving mass. If you wanted to count up all the energy in something, you have to include some that is due to mass-energy. So suppose you want to get a bunch of kinetic energy to blow something up. One way to do that is to convert some chemical potential energy into kinetic energy; that's how dynamite works. Einstein is saying that there's another way: by converting some mass energy into kinetic energy; that's how a nuclear bomb works.
No, what it means are that mass and energy are literally the same, and "mass-energy" is redundant. An object with kinetic energy has more mass than an object with no kinetic energy. A compound with stored chemical energy has more mass than the elements that comprise the compound on their own. An atomic nucleus containing many protons and neutrons has more mass than the sum of those protons and neutrons individually.
Some things have a property called rest mass, which is different than mass. The "term involving mass" in energy calculations that you're thinking of is related to the rest mass (which is represented by m0, not just m). But in every dynamic system, if you use the rest mass instead of the mass when mass is called for, you will get the wrong answer.
Nuclear bombs don't actually convert mass into energy in any way different than that of chemical reactions. In both cases the mass that was lost was the mass of the energy that was released.
The enemies of Democracy are
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
I have not seen anyone answer you. Twenty years ago when I studies such things, 1% for something like a HeNe laser was good. I hear the National Ignition Facility lasers are good to maybe 4%. The quantum efficiency of a laser diode might be as high as 60%. You have a couple of considerations. In an optically pumped laser, you have the efficiency of creating the pump photons. These put the lasing medium in an excited state which happens as some fraction less than 100%. Lastly, the excited state medium can either spontaneously emit, or emit via stimulation. You need the one to start the laser, but any spontaneous emission after that counts towards inefficacy.
http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=307495
Suggests NIF lasers might be 10% efficent http://en.wikipedia.org/wiki/Inertial_confinement_fusion
No, in chemical reactions there is NO change in mass.
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.