Watch how to use light to move matter

boing
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Originally published at: https://boingboing.net/2018/06/29/watch-how-to-use-light-to-move.html

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“Photophoresis denotes the phenomenon that small particles suspended in gas (aerosols) or liquids (hydrocolloids) start to migrate when illuminated by a sufficiently intense beam of light. The existence of this phenomenon is owed to a non-uniform distribution of temperature of an illuminated particle in a fluid medium.”

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Assume I drag my knuckles… is the foil movement due to the surface being heated and creating air currents ?

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Thank you! I gave these away as Xmas ornaments a decade or so ago (with a note to hang in a sunny window after Xmas). Science! It works biatches!

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Did you miss the in a vacuum chamber? The light pushes the foil. Light has mass just a very very very very tiny amount of it.

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Bajoran_lightship_(aft)

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So, you’re saying that the force causing torque was a reaction of heating of the surface followed by some remaining gas molecules in the (incomplete) vacuum chamber bouncing off of it , rather than light pressure? Seems likely, but what would be the experiment to say for sure? Higher quality vacuum demonstrating reduction in torque maybe? Also have to rule out molecules being torn off the foil itself, not sure how to do that.

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The vacuum is not perfect, and as you see in a radiometer, you don’t need many gas molecules to produce torque from heating.

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How to use light to move matter

Flash your lights at someone who’s driving with their vehicle lights off; with any luck, that driver will move to correct the situation.

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the tests have been done already. It is, in fact, affected by the heating of gas molecules which is why crookes radiometer does not work in a strong vacuum. https://en.wikipedia.org/wiki/Crookes_radiometer
Now, if you build a nano light mill like they did at UC Berkeley, you can make a light mill that does not use gas heating to move it.
https://phys.org/news/2010-07-nano-sized-mill-micro-sized-disk-video.html

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I’m sorry, what did you want to know?

image

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Is this how Cyclops happens?

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I haven’t had any success with that experiment over dozens of repetitions in the past year. I think the physics have changed.

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I haven’t decided if I am a particle or a wave.

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Hmm. Yet another issue with cellphone distraction?

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No, I think it’s mostly due to Daytime Running Lights. People drive around with only half-assed headlights on but don’t realize that, from the sides and rear, they are invisible.

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I was interested to see how he’d try to demonstrate this, but I came away with the same assumption I started on, which is that there’s no convincing, easy-to-see demonstration. The effect you’re looking for is so small, and that amount of light can produce so much heat, that it will never be obvious that you’re not seeing some thermal effect. Like, in that vacuum chamber test, I might be seeing the armature buckling, or evaporation from the foil surface, or convection in the less-than-perfect vacuum, or electrostatic effects due to thermionic emission.

I’m sure you can measure light pressure with precision instruments, I just don’t think you can do it in a way that’s both scientifically sound and interesting to look at.

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