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CommissarMega posted:My apologies if this is a dumb question, but can someone explain negative mass to me, like one would a child? Where are you getting your idea of negative mass from? There might be a few equations that bounce around negative numbers, but as far as I know,nobody is proposing negative mass particles. For fucks sake we can't even account for 95% of the mass of our own locally observed galaxy. thrakkorzog fucked around with this message at 12:03 on Mar 30, 2015 |
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Mar 30, 2015 11:49
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thrakkorzog posted:Where are you getting your idea of negative mass from? It's like what's stated before....If you do any amount of interested surfing on wormholes and interstellar travel possibility using them you're going to come into the idea of negative mass..or exotic mass..or whatever they choose to call it.
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Mar 30, 2015 16:21
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I was reading about "glueballs" (hypothetical particles made entirely of gluons, with no quarks) and I was confused by something. Confinement prevents particles with an unbalanced color charge from existing independently, so (detectable) glueballs would have to be color-neutral - in the "singlet" state. But I was under the impression that gluons couldn't form such states - there are only eight 'types' of gluon (corresponding to the eight Gell-Mann matrices) and no combination of them ever adds up to the singlet state. What am I missing?
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Mar 30, 2015 20:39
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Alien Arcana posted:I was reading about "glueballs" (hypothetical particles made entirely of gluons, with no quarks) and I was confused by something. Confinement prevents particles with an unbalanced color charge from existing independently, so (detectable) glueballs would have to be color-neutral - in the "singlet" state. But I was under the impression that gluons couldn't form such states - there are only eight 'types' of gluon (corresponding to the eight Gell-Mann matrices) and no combination of them ever adds up to the singlet state. What am I missing? It's impossible to represent the singlet state as a linear combination of states in the color octet. You can't write down a state for a single gluon that is a superposition of colored states and somehow end up with the singlet state. This doesn't say anything about what happens when you put multiple gluons together.
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Mar 31, 2015 02:43
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I'm researching LIDAR, and it seems like the physics gets tricky pretty quick. Nothing I'm reading has more than a sentence or two on the nitty-gritty. So I still have a few questions in case anyone is familiar on the stuff. How does a higher wavelength relate to longer ranges? Also to some extent, energy levels? An "invisible" wavelength can't damage our eyes, or what? Is the actual concept of backscattering that complicated? I guess the particular method of backscattering changes depending on the target's size and composition, but somehow it still works at all levels. Would you be invisible to the system with a mirror at 45 degrees? Coldstone Cream-my-pants fucked around with this message at 15:37 on Apr 6, 2015 |
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Apr 6, 2015 15:12
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thrakkorzog posted:Where are you getting your idea of negative mass from? Or he could just think it up himself, it's not a crazy idea to say "whoah what if this number in this equation was negative". And then do some research and ask more questions about it.
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Apr 6, 2015 16:29
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The Royal Scrub posted:
An invisible wavelength can absolutely damage your eyes. Looking at the sun during an eclipse is a great way to wind up blind.
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Apr 6, 2015 18:42
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Phanatic posted:An invisible wavelength can absolutely damage your eyes. Looking at the sun during an eclipse is a great way to wind up blind. I was confused by this at first cause I was like "the photons don't change during an eclipse" then I realized that if you weren't informed, you might end up staring at the eclipsed sun for minutes on end, and staring at the sun for minutes on end is a great way to wind up blind.
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Apr 6, 2015 19:09
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SHISHKABOB posted:I was confused by this at first cause I was like "the photons don't change during an eclipse" then I realized that if you weren't informed, you might end up staring at the eclipsed sun for minutes on end, and staring at the sun for minutes on end is a great way to wind up blind. ... blinded by science 
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Apr 6, 2015 19:11
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SHISHKABOB posted:I was confused by this at first cause I was like "the photons don't change during an eclipse" then I realized that if you weren't informed, you might end up staring at the eclipsed sun for minutes on end, and staring at the sun for minutes on end is a great way to wind up blind. It's mostly because your pupils don't contract, which lets more light through than if you were looking at the sun normally.
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Apr 6, 2015 20:39
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Another good example is infrared lasers. You can't see 'em, but they can still dump enough energy into your retinas to turn them into scrambled eggs.
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Apr 6, 2015 21:27
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The Royal Scrub posted:How does a higher wavelength relate to longer ranges? Also to some extent, energy levels? It doesn't, not fundamentally. Like radar, you can use lidar at any wavelength that's convenient. Some wavelengths aren't convenient, for instance if the atmosphere is not transparent at that wavelength, if the detectors are expensive, or if they're not eye-safe. Shorter wavelengths will generally give you better angular resolution, though in practice this is often not the limiting factor. The Royal Scrub posted:An "invisible" wavelength can't damage our eyes, or what? It can, if the light can make it to your retina. Generally this is in the window from 400-1400 nm, which roughly corresponds to the transmission spectrum of water The Royal Scrub posted:Is the actual concept of backscattering that complicated? I guess the particular method of backscattering changes depending on the target's size and composition, but somehow it still works at all levels. Would you be invisible to the system with a mirror at 45 degrees? You can complicate it to the nth degree, but in general for lidar all you need is for some of the light to come back in the direction of the sender. A mirror at 45 degrees would not do that, so lidar would fail to register that point.
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Apr 6, 2015 23:12
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Captain von Trapp posted:Some wavelengths aren't convenient, for instance if the atmosphere is not transparent at that wavelength, if the detectors are expensive, or if they're not eye-safe. Thanks, you are a knowledgeable dude! I feel like I should crack a book instead of asking here, but if the energy level of a photon is a function of its frequency/wavelength, what does a higher power laser do? Just pump out more light? Oh wow, I guess you can't just dial your high tech laser to whatever wavelength you want either? Pretty crazy. Coldstone Cream-my-pants fucked around with this message at 02:08 on Apr 7, 2015 |
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Apr 7, 2015 02:04
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The Royal Scrub posted:Thanks, you are a knowledgeable dude! I feel like I should crack a book instead of asking here, but if the energy level of a photon is a function of its frequency/wavelength, what does a higher power laser do? Just pump out more light? Yes, a higher energy laser pumps out more photons.
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Apr 7, 2015 02:10
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The Royal Scrub posted:Oh wow, I guess you can't just dial your high tech laser to whatever wavelength you want either? Pretty crazy. Most lasers are inherently pretty much single-frequency devices. But there are a few that are fairly broadly tunable, such as Ti:sapphire lasers. You can also get a very broad range of tunable wavelengths through some nonlinear optical processes like optical parametric oscillators/amplifiers. These are still fairly expensive and finicky, so they don't find much use outside research labs yet.
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Apr 7, 2015 02:16
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