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As far as I know, negative energy is theoretically still sound; I may be quite mistaken though. What "energy conditions" would negative energy (or mass for that

by chunky1994 13y ago

As far as I know, negative energy is theoretically still sound; I may be quite mistaken though. What "energy conditions" would negative energy (or mass for that matter) be violating?

solistice 13y ago
Negative refraction is just as strange a concept, and we seem to be slowly getting there technologically. So I'm actually hopeful this will happen someday.
- VLM 13y ago
  Unfortunately negative refraction a secondary effect where you have negative permittivity and permeability at the same time. Negative permittivity is no big deal, metals act like an electron plasma gas around certain frequencies and get all weird, something like the color transmitted thru thin films of gold and how weird gold, silver, copper act in the THz range and all that. The "magic" is creatively negating both .. At The Same Time. Then the negative refraction / metamaterial effects take hold. Kind of like you can compress ammonia (a bit) and nothing terribly interesting happens, and you can cool ammonia gas (a bit) and nothing terribly interesting happens, but do both at the same time and you've invented liquid ammonia and refrigeration and all kinds of nifty stuff. On the other hand energy/mass seems rather fundamental. There are no multiple "easily" negatable components you can play with mixing together. There's no "add a to b to get the mass" going on. So you can't get sneaky with combinations and initial conditions to magically make negative mass/energy. It's really a different kind of problem. The whole topic is pretty interesting to me because the first metamaterial stuff was constructed out of printed circuit boards with weird etchings right around the ham radio microwave 6cm and 9cm bands, which is right up my alley (doing weird ham radio things involving PCBs and such around those frequencies) Unfortunately I have been unable to figure out any practical engineering demo (like, an antenna or a waveguide or some such) that would be ham radio applicable in a real world demonstration. I guess I could make a really weird lens and place it in front of a 6cm horn waveguide antenna, but I can make a much simpler microwave lens antenna using about 1940s tech. Lens antennas using plates of styrofoam and aluminum foil work pretty well at 10 GHz ham radio band for example, but I digress. Metamaterials are kind of a solution in search of a problem right now, like lasers in 1960s or home computers in the 80s or whatever. Most likely, much like the examples, it would be pretty hard to predict today just how important they might be in the future. Or maybe we're seeing the next "magnetic bubble memory" or magnetic amplifier technology or fluidic analog computing or whatever. Hard to predict.
Steuard 13y ago
One reference is here: http://en.wikipedia.org/wiki/Energy_condition http://en.wikipedia.org/wiki/Energy_condition These conditions are widely believed to apply to all realistic matter configurations (to the extent that the less-restrictive ones get used as postulates in some theorems in relativity), though there are some exceptions due to quantum effects (which I believe are usually short-lived). Just for example, a cosmological constant or other dark energy source does not violate the null energy condition. It would be really cool to see any of the energy conditions violated for an extended time in a lab! I'm pretty sure, though, that it has not yet been done.
yk 13y ago
Weak energy condition[1]. In general the energy conditions are useful for analysis of the Einstein equations, but general relativity does not demand them. So violating the energy conditions is somewhat theoretically sound, but one can only say so much about general relativity with violated energy conditions. ( For example a lot of stuff we know about black holes only holds, if some energy conditions are satisfied.) [1] https://en.wikipedia.org/wiki/Energy_condition https://en.wikipedia.org/wiki/Energy_condition

As far as I know, negative energy is theoretically still sound; I may be quite mistaken though. What "energy conditions" would negative energy (or mass for that matter) be violating?

solistice 13y ago

Negative refraction is just as strange a concept, and we seem to be slowly getting there technologically. So I'm actually hopeful this will happen someday.

VLM 13y ago
Unfortunately negative refraction a secondary effect where you have negative permittivity and permeability at the same time. Negative permittivity is no big deal, metals act like an electron plasma gas around certain frequencies and get all weird, something like the color transmitted thru thin films of gold and how weird gold, silver, copper act in the THz range and all that. The "magic" is creatively negating both .. At The Same Time. Then the negative refraction / metamaterial effects take hold. Kind of like you can compress ammonia (a bit) and nothing terribly interesting happens, and you can cool ammonia gas (a bit) and nothing terribly interesting happens, but do both at the same time and you've invented liquid ammonia and refrigeration and all kinds of nifty stuff. On the other hand energy/mass seems rather fundamental. There are no multiple "easily" negatable components you can play with mixing together. There's no "add a to b to get the mass" going on. So you can't get sneaky with combinations and initial conditions to magically make negative mass/energy. It's really a different kind of problem. The whole topic is pretty interesting to me because the first metamaterial stuff was constructed out of printed circuit boards with weird etchings right around the ham radio microwave 6cm and 9cm bands, which is right up my alley (doing weird ham radio things involving PCBs and such around those frequencies) Unfortunately I have been unable to figure out any practical engineering demo (like, an antenna or a waveguide or some such) that would be ham radio applicable in a real world demonstration. I guess I could make a really weird lens and place it in front of a 6cm horn waveguide antenna, but I can make a much simpler microwave lens antenna using about 1940s tech. Lens antennas using plates of styrofoam and aluminum foil work pretty well at 10 GHz ham radio band for example, but I digress. Metamaterials are kind of a solution in search of a problem right now, like lasers in 1960s or home computers in the 80s or whatever. Most likely, much like the examples, it would be pretty hard to predict today just how important they might be in the future. Or maybe we're seeing the next "magnetic bubble memory" or magnetic amplifier technology or fluidic analog computing or whatever. Hard to predict.

Steuard 13y ago

One reference is here: http://en.wikipedia.org/wiki/Energy_condition http://en.wikipedia.org/wiki/Energy_condition These conditions are widely believed to apply to all realistic matter configurations (to the extent that the less-restrictive ones get used as postulates in some theorems in relativity), though there are some exceptions due to quantum effects (which I believe are usually short-lived). Just for example, a cosmological constant or other dark energy source does not violate the null energy condition. It would be really cool to see any of the energy conditions violated for an extended time in a lab! I'm pretty sure, though, that it has not yet been done.

yk 13y ago

Weak energy condition[1]. In general the energy conditions are useful for analysis of the Einstein equations, but general relativity does not demand them. So violating the energy conditions is somewhat theoretically sound, but one can only say so much about general relativity with violated energy conditions. ( For example a lot of stuff we know about black holes only holds, if some energy conditions are satisfied.) [1] https://en.wikipedia.org/wiki/Energy_condition https://en.wikipedia.org/wiki/Energy_condition