Lightmill

The black surface absorbs more of the light energy than the white surface does, and thus becomes hotter. Consequently, when the molecules of the black surface interact with surrounding air molecules, they kick the air molecules away more energetically, resulting in a greater average impulse per interaction than for the white surface. The torque generated is asymmetrical, and the blades spin.

This is actually one of the hardest "simple physics experiments" to explain fully, and neither of the two intuitive answers, one involving thermodynamic heat, the other involving photons, gives a full explanation. Since the black side is going to be hotter because of photon absorption, that answer is more correct than "photons push the blades around", but still does not explain why necessarily the blades would move. Under very slightly different conditions, the blades will not move at all, even if light is shining on the black and white vanes. The best general answer is that there exists an asymmetry, a chirality, in the way the vanes are constructed (one side black, other white), so that given light shining on it, numerous different factors could arise to give the vanes a "push" from both the black and white sides, but not necessarily exactly with equal sum of forces---and thus the vanes will rotate. Maybe, if the sum of forces don't come out too even.

On a deeper level, what I like about this "simple experiment" is that much of the time in physics, there's a conservation law, where "everything balances out in the end", no matter how much you try to unbalance things. But, here, given all the different possible mechanisms that could result in forces upon the white and black sides, it's not necessarily true that all the forces balances out. There is no conservation law guaranteeing that here.

Black surface being a good absorber of light,absorbs most of the light.On the contrary,the white surface being a good reflector reflects most of the light.Considering light as string of photons ,the light reflected from the white surface interacts with the gas molecules and creates a continuum of interacting molecules between the white and the black surface which is aided by the black surface absorbing the light.An impulse is created when the first layer of molecules interact with the black surface which pushes the surface and causes the blades to rotate

Black things absorb more light energy than its white counterpart that reflects all of the energy. Since it absorbs more energy, it heats up faster. The molecules of the black sides will have more kinetic energy due to the heat and will push away at the air molecules more. The asymmetry between the black and white sides pushes the blades in one direction. This causes it to spin.

I first thought that it must be a result of photon momentum, but if that effect was dominant then it would've pushed silver side more than black side as elastic collisions impart more impulse than inelastic ones. I think the increased temperature near black surface increases the local pressure there as volume expansion is constrained a bit for this gas. so this pressure must be driving the machine.

As black objects absorb more light than light colored objects the black fan gets heated up faster as compared to white fan which heats up the surrounding air near it creating a low pressure than the white coloured Fan's surrounding air and because of the pressure difference the air rushes to the black fan making it move and rotating the fan .

Even though it has a complex explanation, which I'm not gonna put here, it's still obvious because of how the sides of the blades are made and some things about light and heat.

Black surface heats up faster thereby heating up the air on its side of the blade. This expands the gas, reducing the pressure on the black side, which causes the blades to be pushed towards the black side as the air/gas on white side is denser and is exerting more pressure.

I suppose the very low pressure is the reason the slight pressure differential from the sides being a different temp is relevant.

Is it the changing temperature I mean does it stop rotating ion steady state? Probably..

I guess of the chamber were at a higher pressure the radiation would heat up the air in in uniform or randomly so it wouldn't rotate much. ..

The black surface of the blade absorbs more energy than the white side and becomes hotter. This results in the black side of the blade expanding more than the white side resulting in force on the blade acting in the direction of the white side. This force acting at a distance from the center of rotation creates torque and causes the blades to spin.

This was just common sense

What is this thing called?

Two intuitive answers. At the very least, one could solve this with simple principals in mind. First, black surfaces will absorb more energy and an increase in energy implies the reverse can occur, expelling energy. That is the most of it. The second is the photon push idea, but understand that this bulb is not a vacuum. These principles apply in space, but not when an object must overcome an atmosphere. This is a safe assumption because, even if you make the hopeful assumption that the bulb could avoid imploding, another answer suggested that there is gas inside.

Black side of the blade absorbs more radiations than white side. As a result, air in contact with black side starts to expand, gets lighter, and push the black side up with more force compared to white side. There is horizontal component of the push which is more on black side and therefore, rotates the wheel in that direction.

let's begin with the color. black is a color which absorb all of the visible light while the white ones reflect it. you can use the pressure method that is pressure increases as heat increases so the black one has a higher pressure than the white one which will cause them to spin. i wish i could help you

For black surface e is greater than white. So black sides warm quickly. They push the white side.