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Is There a Limit To a Laser's Energy?
StartsWithABang (3485481) writes "For normal matter — things like protons, neutrons and electrons — there's a fundamental limit to the number of particles you can fit into a given region of space thanks to the Pauli exclusion principle. But photons aren't subject to that limit; in theory, you could cram an infinite number of them into the same exact state. In principle, then, couldn't you create a laser (or lasing cavity) with an infinite amount of energy inside? Perhaps, but there are some big challenges to be overcome!"
It's the number of sharks you can fit into a given region of space.
Except nex time. Later. Before then.
Infinity doesn't mean what you think it means.
Eventually the laser energy will create a black hole, provided some other exotic effect doesn't occur first. Realisitcally though it's not possible to attain those kinds of photon densities (nothing can reflect anywhere close to well enough for starters).
Napoleon, like anyone can even know that.
http://www.phy.ilstu.edu/ILP/r...
http://www.phy.ilstu.edu/ILP/r...
Etc...
"Update: After a conversation with Chad Orzel, it looks like although there's no limit to the photon energy you can produce, you will at some point--above about 1 MeV in photon energy--start spontaneously producing matter-antimatter pairs of particles whenever your photon interacts with a reflective surface. So at extremely high photon energies, your laser light begins to resemble a matter-antimatter thermal bath rather than merely coherent light."
So it would act like more Star Wars weapons?
Table-ized A.I.
Something worth reading.
For normal matter — things like protons, neutrons and electrons — there's a fundamental limit to the number of particles you can fit into a given region of space thanks to the Pauli exclusion principle.
Wrong, unless you assume space is discretized, which might happen around Planck's length, but has never been proven theoretically nor experimentally.
If you did physics like me then it's not that mysterious. There are some problems. The particles would burn through the cavity long before 'it' got 'infinite,' not that that sentence makes any sense whatsoever. Also where the !@#k are you going to get infinite power to pump the stupid thing?(!)
Billions and billions of years ago, even before lord Xenu, there was a scientist who pulled this off.
Blext Telfrawd, an A type Hixoid, did get an infinite number of protons into a finite space. Then the containment field faltered, obliterating the iteration of his universe..
Most historians agree this was tragic for it ended his universe, and created one with Justin Bieber. Sentients who were able to achieve trans-dimensional universital access, send a message to you from the past: It's just too risky to repeat the so called "Bieber Event",
You've been warned.
Another consultant who stuck it out.
"We are the Priests, of the Temples of Syrinx..."
Okay. Interesting on a theoretical level.
The main problem with testing this is "how does one generate infinite or near-infinite energy" to power something like this?
Of course, if we've answered that, we're ALREADY in a place where we've either wiped ourselves out (accidentally or otherwise), or we've basically solved the greatest real-world problem in the history of humanity.
Chas - The one, the only.
THANK GOD!!!
I got nothing.
But what a great what-if question you could forge from it.
The energy of a photon is characterized by its wavelength. In a laser, the wavelength is constant. You have a large amount of photons which are coherent but at an almost single wavelength. When the article is talking about 1 MeV, it falsely interprets this as if the laser is emitting a single photon at 1 MeV. That is not what happen. It emits many photons in coherence which the sum of energy of all the individual photons will reach 1 MeV or more. Each photon cannot create an electron-positron pair and all photons collectively cannot create an electron-positron pair.
A 1 MeV photon would be a gamma ray photon and it is not true at all, your laser doesn't change its wavelenght as more more "energy" is emitted. In fact, we should instead talk about the power of the laser rather than its energy. The power being the amount of energy emitted by unit of time.
Achille Talon
Hop!
Eventually the laser energy will create a black
hole
There is a specific term in astrophysics for such a theoretical object:
http://en.m.wikipedia.org/wiki...
Is it more or less than the times you can spam your own blog on Slashdot? Coz that's all I really care about.
Would it be effective against a Dikironium cloud creature?
"The average reporter we talk to is 27 years old......They literally know nothing." - Ben Rhodes
I found this a better analysis
Are Black Hole Starships Possible?
But long before that happens the question is if the laser can remain a laser.
A laser needs some kind of nonlinearity in the medium. Any nonlinearity introduces a scale. So the real question is: At which power does of-resonant driving cause transitions (e.g. Landau-Zener) or of-resonant shifts (Stark shift) and can you actually theoretically contruct a medium which fulfills the criteria to serve as a lasing medium for an arbitrary large scale of power?
As a starting point for an examination of such questions i recomment the Quantum Optics Toolbox for Matlab by Sze Tan.
How much energy would one need in order to fire a laser so powerful the atmosphere would just instantly ignite.
I just need to know for, hmm, educational purposes. I am not an evil-doer, honest. That guy over there is, get him.
Really though, the amount of power to come out of these lasers to be SUSTAINED beams would be immense.
We are talking fusion-power generations here. And we are trying to ignite a fusion reactor WITH a powerful laser! The madness!
Hopefully one day. Fusion has the ability to change everything about our society once we get around the initial hurdle of making the damn thing work and getting it smaller and more optimized.
If you can channel the energy of a fusion explosion into many lasing-while-ionizing rods (think "Real Genius"s death ray laser, but MUCH larger) you could pack so many X-Ray photons into a burst that the impact (momentum transfer) alone destroys the target's armor, at least according to David Weber.
42
There was an article from 2010 that talked about the theoretical limit to laser beam energy. From the article:
"At high laser intensities interaction of the created electron and positron with the laser field can lead to production of multiple new particles and thus to formation of an avalanche-like electromagnetic cascade"
Here's the link to the article in question: http://physicsbuzz.physicscent...
That article was ultimately using this article as a source.
Stop creating these stupid web layouts. With the full screen opening page and the rest below.
Theoretically there is a definable limit to the number of photons of a given energy that can be constrained within a specific region. It comes from the fact that photon interactions with normal matter transfer energy see https://en.wikipedia.org/wiki/Radiation_pressure. So that containing photons by reflection in present laser equipment does exert an infinitesimal force outwards on the mirrors.
So as I see it the limit is one of how well made the laser containment equipment is manufactured, but there is a limit where no material could resist the tendency for the device to tare itself apart, I leave it to the reader to do the actual engineering math to work out what that is.
The article outlines how lasers work but it's basically this: If we could build powerful lasers, which we do not know how to do due to technical issues, we had powerful lasers! Awesome!
Car analogy: There is no theoretical limit how far you can drive with your car! If we could build cars that drive further, we could drive further with our cars! Even an infinite mileage seems possible! Awesome!
It is well-known that once you exceed a certain energy density you create a black hole. This is why the Death Star superlaser consists of multiple small lasers that combine.
That's why ZPMs eventually go flat.
IANAP. Which means, i probably have a better understanding of the subject than they do. Theoretically.
As a certain energy density, the radiation pressure from the photons will be stronger than the tensile strength of the optical cavity, and the laser will blow apart. In astronomy, a similar limit is called the Eddington limit, so this is really the Eddington limit for a laser.
The radiation pressure is (ignoring all factors of 2 or cos(incidence)) E / c. A tensile limit, T, of 500 mega pascals (reasonable for steel) thus would imply an energy intensity of c T, or 1.5 x 10^17 Watts/m^2. If the total cavity had an area of 1 m^2, then that's ~ 10^17 Watts.
Note that it is common in pulsed lasers to have a lot of energy in a very short pulse (so the actual power during the pulse is very high). If your pulses were a microsecond in length, then the Eddington limit per pulse would be about 10^11 Joules, equivalent to 24 tons of TNT.
all photons collectively cannot create an electron-positron pair.
This is false. Multiple photons can participate in an interaction and work with their combined energy. The probability of this happening is rather low compared to a single photon (and for pair production, it is rather in-efficient until you get above a couple MeV anyway), but typically the effect is also quite non-linear in terms of intensity. This is seen with laser induced breakdown of material. No individual photon has the ionization energy, and the particular material does not have a transition level that matches the photon, so it is not a matter of exciting the atoms first. Instead, there is a small chance that two photons (or more) will interact at the same time to combine energy and ionize the atom.
This effect is important and useful because of the non-linear response to intensity, so that if you focus down a beam you can get a very small region of activity, instead of a gradual increase in activity as you approach the focus point.
They've already ran into this issue with fusion power generation via lasers. When they increase the laser output too much, the laser light decreases. Turns out the photons are spontaneously turning into matter at high energy densities. This issue has been known about for years.
At high enough energies particles are spontaneously created. They in turn will obey Pauli Exclusion (at least if they have spin I think). So enough photons and you make matter that will prevent you from making more particles ie pumping more energy into the space.
This effect will not only kill at high energies but at high intensity too. With a high enough intensity you can have multi-photon interactions to achieve the same total energy. However pair production is not the only process you have to worry about compton scattering will occur as well. This will impose an intensity limit well below pair production energies.
Essentially reflected photons will have less energy than incident photons and as the energy increases so too does this energy difference. It is caused by relativistic effects when a photon is reflected from an electron. At visible wavelengths the effect still occurs but is not noticeable but crank the energy up to several keV and your photon has an energy more comparable to the electron rest mass energy and the effect kicks in.
Eventually the laser energy will create a black hole, provided some other exotic effect doesn't occur first.
That's a limit on energy density, not total energy in the laser. In principle you could use a very WIDE laser opterating below the black-hole thrshold and focus the beam externally (which, if it's powerful enough, it might do eventually, by self-gravitation, after leaving the cavity, even if the cavity geometry made it emit a colimated, rather than a converging, beam.) Thus, making a kugelblitz with a (very wide) laser might be theoretically possible (if "some other exotic effect" didn't make the required laser cavity to wide to be physically realizable).
I'd imagine "Some other exotic effects" might include the electric field component of the coherent light becoming strong enough to polarize the vacuum and create particle-antiparticle pairs from multiple photons, dissipating their energy, somewhere WAY below the threshold of gravitic-collapse effects. So you'd need a REALLY WIDE laser and REALLY GOOD optics to make your external-to-the-laser black hole.
Of course the question, being phrased in terms of Bose-Einstein vs. Fermi-Dirac statistics and "infinite" energy was really about energy density in the cavity - just poorly phrased. So you answered the question that was REALLY being asked.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
"Physics" is not just one thing anymore. The guy writing TFA, Ethan Siegel, is a bonified professional physicist. Reading the comments, you can see he just didn't know this one thing as well as he thought. How does that happen?
I don't know that there's any physicist going through training today or in the last 20 years who really understands "all" of physics.
Physics PhDs learn most of physics up to about 1910 (even that is a stretch, but at least the complete fields up to that point are introduced and sketched out), and the next 100 years are based on your specialty. The limits of energy density for photons are usually in this realm of "introduced only if directly important to your specialty."
It's up to the individual to fill in the gaps after formal classes, and it can be very hard to figure out what you don't know. It's particularly hard because of the oversimplified way physics is generally taught in undergrad, even to physics majors. Your old reference books may not actually be correct. I'm sure I've got a physics textbook around which claims almost exactly what Ethan said in his blog; the "why" of pair generation is just too distracting.
On a related note, I asked this quessie at a laser pointer forum a while back. Would still be interested in hearing a real answer: http://laserpointerforums.com/...
Why OpalCalc is the best Windows calc
They're unreadable without a tablet.
Bose-Einstein Condensate! In more detail, fermions cannot be crammed together but in certain conditions, Bosons can. Photons are a type of Boson but not the only one. The Pauli exclusion principle does not apply to Bosons! Looks like a non-specialist needs to read some books on this concept. I won't even go into deeper details without this point being crystal clear!
The inability to focus light to a small enough region of space. At a high enough intensity it will start pair production of electron and positron and that will dissipate the energy. If you can get pass the pair production problem then there is the mini black hole problem.
The author is a crank.
Compressed light has been an area study for me for a while.
What if photons stopped generally not interacting with each other and instead reacted strongly. Suddenly.
Imagine what would happen if an area was filled relatively speaking with intense laser light and suddenly converted to an interactive state. It would either explode violently if the particles repelled, or form a singularity if they attract. The former is more likely. Thus all you need to make a bomb is a nice light source, perhaps even a star would work.
How do you get photons to react like that? Aren't they moving too fast and without mass? The way you do this is by imposing the influence from an exterior dimension upon a small area of normal space, in this case one where photons are not massless or infinitely fast. Basically, you'd cancel both of those things at once and the pile of photons would 1, hit a brick wall with enormous force, and 2, do it with effectively infinite mass. C condensed turns into an awful lot of E, in a hurry.
So you need a cavity with a suitable photo source, a cargo container would work. Attach photon source, power source, and scatter photon converters as needed around the container. Turn it on, fill it with nice tasty photons, and then condense them. Bang. Hope you weren't close.
If this sort of large effect is not desired, you can still play with it by condensing single photons at a time. The explosive effect is smaller, more useful and the components needed are easier to get.
Causing other dimensions to exert influence here is a huge area of potential. Not only do we have the physics we think we know, you also get physics from another universe where the laws are different. Combining parts of them together yields effects that border on magic, and it doesn't violate our laws of physics because our laws don't apply. The basic problems with it are that it's hard to obtain and use these influences because our technology is not there yet. At all. And secondly, we don't understand all the effects. Hell, we understand none of it. It's like trying to understand an entire physics model unlike anything you think you know. Nothing is the same. And oh by the way, there;s not just one of these but dozens and they're all different. Nobody can understand all of it, not even Einstein if he was alive. He managed one about as well as anyone can. This is several orders of magnitude above that.
Most of it is also lethal to humans. Lots of loose radiation from any/all of this stuff. It's very unhealthy. Nothing like taking the smartest people you have, or anyone has, and have them try to work it it, only to have it manifest in an unexpected way and kill everybody. To make it worse, it's hard to tell if we've failed to understand it or if the influence is being manipulated to cause failures. It is not in anyone's interest for anyone of us to achieve success. Much better to have it all fail via "accidents" and be perceived as too dangerous to even try.
man this medium page is but guly.
giant fonts, no use of the screen.
bleark.
"Life is short and in most cases it ends with death." Sir Sinclair
How many balloons can you pop with that?
The article reads as somewhat naive to me.
Every material has an energy density limit, at which point it will breakdown or ionize.
And given that no material is completely transparent to any wavelength, once you produce enough energy density, every material will ionize and place an upper limit on laser propagation.
and a zero point module
Now you know how Photon Torpedoes work....
Is that when a sweaty guy in a Vneck, chest hair puffed out, gold chain on his neck, wont let you into "da club" ?
The guy who said the election was rigged won the presidency with the second-most votes.
I think the real question is, at what point does the resonance cascade occur and open up a portal to Xen?
If space-time would not exist as we know it these days, as in Einstein's theories, light could be two dimensional. A line.
A photon then could be a field, extending in front of it, and trailing it, basically generalized as a photonic particle [the average photon].
Such a field, for instance measured as velocity, but call it energy, since distance doesn't really exist, neither does place, has a maximum value.
The amount of energy within this universe you can put from A to B has a limit.
Einstein would have been very mad if you would ask him how many photons there would somewhere -at the same time at the same place-.
Anyway, simply put, if you put too much energy in one spot we call it matter.
[since this universe allows for the crystallization of energy into matter]
I'm probably wrong though, because I am not a theoretical physicist.
Einstein is still right, so it doesn't matter.
I think we should call space-time Ether, as that follows the human reasoning about a medium.
Finally an intelligent comment, as counterpoint to all the mental masturbation. :p The word "theoretical" here is meaningless, since one discipline's theory is another discipline's practice. Practical limits rule ALL engineering systems, and eventually it becomes impossibly expensive to surmount the next more difficult one.
I propose an even lower limit than light pressure - ionization potential. There are two cases: gas laser and solid state.
In the case of a gas laser, the electric field strength at the cavity wall must stay below the ionization potential of the wall material, or else the cavity wall erodes. Even if you postulate a device where the active medium is cavity wall plasma, and there is no reason to suppose such a combination of materials can ever exist, erosion will still cause the cavity to change size, ruining the optical tuning. Even movable end mirrors can't compensate indefinitely, and the cavity simply burns out.
The solid state case is even easier. The maximum tolerable E-field is the ionization potential of the active medium, which again burns out the cavity, but this time volumetrically, not from the surface.
Most respondents have interpreted the question as "What is the maximum E-field that free space can support." This is a different question, which has nothing to do with lasers. Slashdot's computer geniuses clearly understand not plasma physics, material science nor lasers. :(
I used to think I'd never see a resonance cascade. Then I took an arrow to the knee.