Interesting (to me, anyway) question about theoretical visual.

[The Kilted Yaksman]

I read this one somewhere a while back and have never seen anybody with a good scientific background take a whack at it.

Suppose, sometime in a Star Trek like future, you are able to manufacture a large perfect sphere, say 5m in diameter, and make the interior surface mirrored, and leave it floating in a zero G environment. If you were to have Scotty (or O'Brian I suppose) teleport you into the center of that sphere, and you were to then turn on a flashlight, what would you see? I have seen some of the weird optical effects of large concave mirrors, but I just can't wrap my brain around this one.

 

[madurobob]

Suppose, sometime in a Star Trek like future, you are able to manufacture a large perfect sphere, say 5m in diameter, and make the interior surface mirrored

what the little "m" in "5m" stand for? Miles?

I imagine you'd see a very (very) faint general glow from the direction you point the flashlight. A more interesting question may be what you'd see if you had a very powerful laser pointer and what happens when you move your hand.

But, I am prepared to be wrong.

ETA: in a sphere, is the center also the focal point for any given quasi-parabolic section of the inside of the sphere? I don't think so...

 

[JoeTheJuggler]

I have seen some of the weird optical effects of large concave mirrors, but I just can't wrap my brain around this one.

I can't even understand how the one with two opposing parabolic mirrors (the top one with a hole in it) works. It's the thing sold as the Mirage 3D Illusion (sometimes called a "hologram generator").

I'm guessing you'd see some really strange reflections of yourself inside your mirrored sphere. I guess what you'd see would depend on where you look compared to where you're shining the light.

Something I'd love to have seen done by Escher!

 

[Michael Gray]

Do you mean:
1) A hypothetically "perfect" set-up, vis: a perfectly reflecting mirror surface, a point light source etc, all located at the exact centre of the sphere (a point detector would render the question moot, btw)
or
2) A realistic scenario, such as a real flashlight, a real eyeball, etc, with real 'jiggles' and so-on?

 

[The Kilted Yaksman]

2) A realistic scenario, such as a real flashlight, a real eyeball, etc, with real 'jiggles' and so-on?

This ^
5m = 5 meters.

1."teleport" in.
2.Turn on flash light.
3.?
4.Profit

 

[GreyICE]

I can't even understand how the one with two opposing parabolic mirrors (the top one with a hole in it) works. It's the thing sold as the Mirage 3D Illusion (sometimes called a "hologram generator").

I'm guessing you'd see some really strange reflections of yourself inside your mirrored sphere. I guess what you'd see would depend on where you look compared to where you're shining the light.

Something I'd love to have seen done by Escher!

It's reasonably simple. You'd see a very bright light.

You see with perfectly reflective mirrors, the light from the flashlight would only terminate against your body. As the only absorber, a fair amount of it is going to terminate in your eyes.

Since the light is going to be endlessly refracted off your skin and clothing, it's probably going to have tonal variances based more or less on your average skin color and clothing color.

I can't imagine much else. There's going to be a lot of paths to your eyes.

If you mean a 5 MILE radius sphere, you'll see nothing. The light level dissipated over five miles will be too low to register as illumination on your eyeballs.

 

[Myriad]

It's reasonably simple. You'd see a very bright light.

You see with perfectly reflective mirrors, the light from the flashlight would only terminate against your body. As the only absorber, a fair amount of it is going to terminate in your eyes.

Since the light is going to be endlessly refracted off your skin and clothing, it's probably going to have tonal variances based more or less on your average skin color and clothing color.

I can't imagine much else. There's going to be a lot of paths to your eyes.

If you mean a 5 MILE radius sphere, you'll see nothing. The light level dissipated over five miles will be too low to register as illumination on your eyeballs.

I agree with everything except the difference for the 5 mile radius sphere. Given a perfectly reflective inner surface, the size of the sphere makes little difference until it gets big enough for the time it takes the light to travel to make a difference.

Also, given the perfectly reflective inner surface, it would get rather uncomfortably warm in there.

Respectfully,
Myriad

 

[GreyICE]

I agree with everything except the difference for the 5 mile radius sphere. Given a perfectly reflective inner surface, the size of the sphere makes little difference until it gets big enough for the time it takes the light to travel to make a difference.

Also, given the perfectly reflective inner surface, it would get rather uncomfortably warm in there.

Respectfully,
Myriad

Theoretically, that seems likely (the light still all has to end on your body) but it seems wrong for some reason. Probably because we're too used to non-perfect surfaces.

 

[Modified]

Also, given the perfectly reflective inner surface, it would get rather uncomfortably warm in there.

I don't think absorbing the entire energy output of a common flashlight would get you all that warm. Or maybe the surface of the sphere is a perfect insulator as well, but then you'd get pretty warm anyway, and the flashlight would make little difference.

I'm not sure it would get all that bright either, since your body (besides retinas) would be absorbing a lot of the light. Assuming you were naked, you'd see a combination of light reflected from the surface only and light reflected one or more times from your body, so maybe a dim, somewhat fleshy colored glow from all directions. If you were also wearing a perfectly reflective suit with just your eyes exposed, then it would get awfully bright.

 

[GreyICE]

I don't think absorbing the entire energy output of a common flashlight would get you all that warm. Or maybe the surface of the sphere is a perfect insulator as well, but then you'd get pretty warm anyway, and the flashlight would make little difference.

I'm not sure it would get all that bright either, since your body (besides retinas) would be absorbing a lot of the light. Assuming you were naked, you'd see a combination of light reflected from the surface only and light reflected one or more times from your body, so maybe a dim, somewhat fleshy colored glow from all directions. If you were also wearing a perfectly reflective suit with just your eyes exposed, then it would get awfully bright.

Eh, the flashlight is what, a few watts? Not an issue.

The big 250 BTU space heater we're carting around is a bit of an issue.