Topic: What are these spin in the sun thingies called?

[glassobsessed]

I have been trying to remember what these thingies are called, I have tried various ways to find out but so far all have drawn a blank.
I hope that some brainy member of the GMB will know.

The vanes at the top spin round and round when it is sunny, any other information anyone can add would be welcome.

Thanks, John.

[Max]

I didn't even know they had a 'name'!  I'll be interested to find out what it is too!

[dirk.]

http://en.wikipedia.org/wiki/Radiometer

[glassobsessed]

Thank you Dirk, so they are Crookes Radiometers made as novelties but still a crude way of measuring (in this case) sunlight. The more light the faster it spins, and apparently a minor mystery as to how they work.

I kept searching using helio..... it would have taken me years (if ever) to look under radio....

Max, we are now in the know.

John.

[Max]

You're such a brainiac Dirk!   :hiclp: :hiclp:  Hope I remember the name for them!

[dirk.]

  ...little lucid moment... 

[jonchellycain]

ok the other half reckons one side of the panel is black and one is white, the black attracts the light and the white reflects/deflects the light and there is a pull between them, the more light the more pull and so because its set on a needle it spins around on its axis...not that any of that makes an once of sense to me plus he may be completly wrong

[obscurities]

http://en.wikipedia.org/wiki/Crookes_radiometer

An explanation of how the Crookes Radiometer works is here....  There are two principals at work at the same time, and it is unknown which is stronger.... 

[glassobsessed]

The explanations described in Wikipedia and by Michelle's other half don't do it for me.

I like the idea I read or heard somewhere that light bulbs do not actually emit light (photons) but really suck dark out of the air. Applying this principle to the black and white vanes leads me to conclude that the black side of the vane sucks in these photons for the white side to spit them out. So, as we have all read (and in my case misunderstood) 'action and reaction are equal and opposite' this spitting or emitting of photons creates a force which turn the vanes on the spindle. Simple.

John.

[obscurities]

John,

I like your explanation much better... It is easier to understand and makes more sense.

Craig