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Real one way glass

Posted: Tue Jan 03, 2017 7:20 pm UTC
by liberonscien
If I understand the physics correctly, there is no such thing as one way glass, i.e., glass that only allows light to pass through from one side. What could be done with such an anomalous kind of glass?
To clarify, this glass is also a perfect mirror because if this glass was to absorb energy from the other side then the glass would violate the one way rule.

Re: Real one way glass

Posted: Tue Jan 03, 2017 7:33 pm UTC
by Flumble
I'll start off with: reducing entropy and thereby violating the second law of thermodynamics.

Re: Real one way glass

Posted: Tue Jan 03, 2017 8:18 pm UTC
by gmalivuk
A sphere of the stuff that lets light in but not out would make a convenient solar battery or time bomb, depending on how quickly it released stored energy.

Re: Real one way glass

Posted: Wed Jan 04, 2017 8:53 am UTC
by quantropy
liberonscien wrote:If I understand the physics correctly, there is no such thing as one way glass?

Is this true though? After all in electronics you have diodes, and as far as I can see the same physics applies. It's true that diodes don't work at thermal energies, preventing the building of a Maxwell's demon device, but it seems to me that the corresponding argument would be that one-way glass wouldn't work if it were at the temperature of the sun.

Re: Real one way glass

Posted: Thu Jan 05, 2017 5:05 pm UTC
by jewish_scientist
gmalivuk wrote:A sphere of the stuff that lets light in but not out would make a convenient solar battery or time bomb, depending on how quickly it released stored energy.

Wait... if it lets in all photons regardless of their frequency or angle, then wouldn't this sphere be a black body?

Re: Real one way glass

Posted: Thu Jan 05, 2017 5:23 pm UTC
by Thesh
I would make a badass pair of sunglasses.

Re: Real one way glass

Posted: Thu Jan 05, 2017 5:24 pm UTC
by gmalivuk
In but not out, I said.

Re: Real one way glass

Posted: Thu Jan 05, 2017 5:54 pm UTC
by Thesh
gmalivuk wrote:In but not out, I said.

Like this?

https://en.wikipedia.org/wiki/File:Blac ... zation.png

Re: Real one way glass

Posted: Thu Jan 05, 2017 6:05 pm UTC
by gmalivuk
How's that supposed to prevent light from coming back out the hole it went in?

In any case, we'll need the OP to clarify exactly what's meant by one-way, as I was taking it to mean thermal radiation also doesn't pass back the other way (hence its being impossible).

Re: Real one way glass

Posted: Thu Jan 05, 2017 6:21 pm UTC
by Zamfir
gmalivuk wrote:How's that supposed to prevent light from coming back out the hole it went in?

Out-of-arrows-error.

Re: Real one way glass

Posted: Thu Jan 05, 2017 6:33 pm UTC
by Thesh
gmalivuk wrote:How's that supposed to prevent light from coming back out the hole it went in?

In any case, we'll need the OP to clarify exactly what's meant by one-way, as I was taking it to mean thermal radiation also doesn't pass back the other way (hence its being impossible).


It's just a visualization. Anyway, they said light does not pass through it in one direction; I assume that means the other direction they get absorbed, which means it could radiate that as heat. If it was also perfectly reflective, then that's another story - and another physical impossibility, I believe.

Re: Real one way glass

Posted: Thu Jan 05, 2017 8:02 pm UTC
by Flumble
gmalivuk wrote:In any case, we'll need the OP to clarify exactly what's meant by one-way, as I was taking it to mean thermal radiation also doesn't pass back the other way (hence its being impossible).

I'm going with this, too.

And also what's meant by "glass". If it's the regular optical stuff, we're bound to reversibility like in that one what-if.

Re: Real one way glass

Posted: Thu Jan 05, 2017 8:04 pm UTC
by speising
gmalivuk wrote:How's that supposed to prevent light from coming back out the hole it went in?

In any case, we'll need the OP to clarify exactly what's meant by one-way, as I was taking it to mean thermal radiation also doesn't pass back the other way (hence its being impossible).

When people talk about light, they typically mean visible light, not thermal radiation. Specifically in the context of one way mirrors.

Re: Real one way glass

Posted: Thu Jan 05, 2017 8:16 pm UTC
by liberonscien
gmalivuk wrote:How's that supposed to prevent light from coming back out the hole it went in?

In any case, we'll need the OP to clarify exactly what's meant by one-way, as I was taking it to mean thermal radiation also doesn't pass back the other way (hence its being impossible).

Energy can pass through it, but in one direction only.

Re: Real one way glass

Posted: Thu Jan 05, 2017 8:25 pm UTC
by liberonscien
Thesh wrote:
gmalivuk wrote:How's that supposed to prevent light from coming back out the hole it went in?

In any case, we'll need the OP to clarify exactly what's meant by one-way, as I was taking it to mean thermal radiation also doesn't pass back the other way (hence its being impossible).


It's just a visualization. Anyway, they said light does not pass through it in one direction; I assume that means the other direction they get absorbed, which means it could radiate that as heat. If it was also perfectly reflective, then that's another story - and another physical impossibility, I believe.

One side allows light to pass through. The other is a perfect mirror.

Re: Real one way glass

Posted: Thu Jan 05, 2017 9:26 pm UTC
by Thesh
Hmm... But if you tried to make them into sunglasses, the reflection of your eye might appear to be superimposed on the image, and they just wouldn't be useful. I'm not sure there would be any legitimate use for that, then.

Re: Real one way glass

Posted: Thu Jan 05, 2017 10:00 pm UTC
by gmalivuk
...except for light bombs and solar batteries

Re: Real one way glass

Posted: Thu Jan 05, 2017 10:04 pm UTC
by PeteP
I think that does get around the whole "can't make something hotter than the source with passive optics" doesn't it? So fuck entropy!

Re: Real one way glass

Posted: Fri Jan 06, 2017 1:28 am UTC
by liberonscien
gmalivuk wrote:...except for light bombs and solar batteries

Death rays?

Re: Real one way glass

Posted: Fri Jan 06, 2017 2:00 am UTC
by Thesh
gmalivuk wrote:...except for light bombs and solar batteries


Well, I was aiming a little higher than you.

Re: Real one way glass

Posted: Sat Jan 07, 2017 6:43 am UTC
by liberonscien
It occurred to me yesterday that such a piece of glass could be used to boost the signal range of an electronic device. What do the other users of this thread think?

Re: Real one way glass

Posted: Fri Jan 13, 2017 2:55 pm UTC
by peregrine_crow
Inverting gmalivuk suggestion, we could also use this to passively cool stuff. Make a sphere out of it with the reflective side on the outside and whatever is inside should reach absolute zero eventually (possibly after an infinite amount of time). Alternatively, you could make a heat shield out of it and have something survive flying through the sun.

Re: Real one way glass

Posted: Tue Jan 17, 2017 11:04 pm UTC
by liberonscien
Now what if one side is one way and the other side just absorbs the energy?

Re: Real one way glass

Posted: Tue Jan 17, 2017 11:33 pm UTC
by LaserGuy
liberonscien wrote:Now what if one side is one way and the other side just absorbs the energy?


You can do this using an optical isolator.

Re: Real one way glass

Posted: Wed Feb 01, 2017 2:07 pm UTC
by jewish_scientist
If light enters the sphere and cannot leave via thermal radiation or some other means, then the result will be a kugelblitz given enough time.

Re: Real one way glass

Posted: Wed Feb 01, 2017 9:42 pm UTC
by liberonscien
jewish_scientist wrote:If light enters the sphere and cannot leave via thermal radiation or some other means, then the result will be a kugelblitz given enough time.

Interesting. This kind of glass could, theoretically, be used to create a black hole? Interesting. This kind of glass could then be used to create doomsday devices besides capturing the sun's light and using it as a death ray.

Re: Real one way glass

Posted: Wed Feb 01, 2017 9:53 pm UTC
by PeteP
Well it would also have to be indestructible because otherwise the radiation pressure will tear it apart before that.

Re: Real one way glass

Posted: Thu Feb 02, 2017 3:26 am UTC
by liberonscien
PeteP wrote:Well it would also have to be indestructible because otherwise the radiation pressure will tear it apart before that.

Well, it is a perfect reflector of all light.
I now realize that it would be somewhat difficult to work with. It would be difficult or impossible to cut with lasers.