Superconductivity for light beams?

  • #26
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Not sure I follow. A stream of electrons exactly constitutes a current, why would this be disqualified?
I made a mistake. Yes, you are right. But what I want is controllable current which can transmit information, just like telephone or fiber optics. I have no idea if a stream of electrons in vacuum can do this.
 
  • #27
berkeman
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I made a mistake. Yes, you are right. But what I want is controllable current which can transmit information, just like telephone or fiber optics. I have no idea if a stream of electrons in vacuum can do this.
They can, over a short range.
 
  • #28
jbriggs444
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I made a mistake. Yes, you are right. But what I want is controllable current which can transmit information
You can always turn the floodgates on and off on a dam and monitor water levels downstream.
 
  • #29
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I'm a bit surprised to not see the obvious answer here: the most lossless medium for current and radiation is ... space vacuum.
Fixed it for you.
 
  • #30
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Do you mean "space" or "vacuum"? "Space" isn't a medium. A volume of space may contain a medium, or more than one medium.

Zz.
As I recall, someone on this forum said that light doesn't require a medium. I argued, and put forth a "theory" of how vacuum was a medium. My post was deleted by an "official" of this forum.
Something no one mentioned is that non-focused light dissipates as the square of the distance, even if there is no loss from the medium.
 
  • #31
berkeman
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As I recall, someone on this forum said that light doesn't require a medium. I argued, and put forth a "theory" of how vacuum was a medium. My post was deleted by an "official" of this forum.
Sounds appropriate. Personal speculation is not allowed here. If you had a problem with the Moderation, per the PF Rules you should contact the Mentor involved. [/off-topic]
 
  • #32
ZapperZ
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As I recall, someone on this forum said that light doesn't require a medium. I argued, and put forth a "theory" of how vacuum was a medium.
I'm not impressed. "theories" like that are a dime a dozen on the 'net. Publish it, then you can boast about it on here. Otherwise, join the queue.

Something no one mentioned is that non-focused light dissipates as the square of the distance, even if there is no loss from the medium.
What does this have anything to do with a "medium"? It is simply a geometric effect due to 3D space. An electrostatic field from a point source has the same 1/r2 dependence. Has nothing to do with space being a medium or not.

Zz.
 
  • #33
phinds
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I'm a bit surprised to not see the obvious answer here: the most lossless medium for current and radiation is ... space.
No, space is not a good conductor of electric current at all.
 
  • #34
davenn
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No, space is not a good conductor of electric current at all.
that's correct, but it doesn't stop a stream of electrons flowing ( controlled or otherwise) between two points in a vacuum :smile:
 
  • #35
phinds
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that's correct, but it doesn't stop a stream of electrons flowing ( controlled or otherwise) between two points in a vacuum :smile:
But is that current? Can it do work? (particularly sustained work?)
 
  • #36
davenn
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But is that current? Can it do work? (particularly sustained work?)
yes it's current ... how do you think an tube works ?

Electron-Tube-EL34-B-6V6GT-6146B-6L6GT-6146-EL34-B-.jpg



or the older TV picture tube ?

monito6.jpg


There is a current flowing from the cathode to anode across the vacuum :smile:


Dave
 
  • #37
phinds
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AAAGGG. Tubes. I hate tubes. Bah humbug.
 
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  • #38
davenn
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AAAGGG. Tubes. I hate tubes. Bah humbug.
They were wonderful things for keeping the radio shack warm on cold winter nights :smile:
 
  • #39
phinds
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They were wonderful things for keeping the radio shack warm on cold winter nights :smile:
Yes, and they were TERRIFIC in Mcintosh amps and preamps but I still hate them. It's a long story.
 
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  • #40
DrDu
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While superconductivity requires charged particles, in some special media, light can behave as a superfluid, i.e. propagate without losses. I think we had an article in the news section just some days ago:
https://phys.org/news/2017-06-stream-superfluid.html
 

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