Sometimes when I'm in bed at night, I rub my feet against the sheets and light is created. What exactly is going on?

I'm familiar with static electricity, and the triboelectric effect (creating a charge by rubbing 2 insulators together), and electrostatic discharge (releasing charge by touching a grounded conductor).

I believe that all of that is what is at work here, but I'm slightly confused since in other cases, the triboelectric effect and electrostatic discharge seem to occur as two separate steps, with different substances involved, and here, the two effects seem to be occurring simultaneously, with the same substances.

Can someone help me with a step-by-step explanation of the dynamics of what is going on?

  • $\begingroup$ Please tell, do you wear nylon socks or something to bed? Does your bed have metal frame or wood? What are your sheets made of? These things may be helpful in answering $\endgroup$ – Rijul Gupta May 9 '14 at 13:57
  • $\begingroup$ I totally believe you. I expericed the same thing during by early childhood. I also got that effect once ever in a different bed much later and could never get it again there. Again while I was on a trip that went so many places, during the one night I was in Munich Germany, I generated light but a different way. I could keep rubbing a specific two sheets in that bed together and generating light on command unlike before. $\endgroup$ – Timothy Mar 19 at 22:59

So this is a very simple potential-kinetic energy scenario. When you rub them together, charges get moved from one object to the another. Then, the potential thus created pulls the charge back, and it jumps back again. But as it comes back, it gains kinetic energy. So when the charge bumps into the object it has originally come from, the sudden deceleration causes it to emit light, just as any other accelerated charge would emit radiation.

This very phenomenon is also behind the production of heat and light when you burn a fuel. Because heat is nothing but radiation in the infrared range.

  • 1
    $\begingroup$ Nice answer. My understanding is that the charge crashing into and ionising molecules in air leads to an avalanche effect (more and more accelerated ions) so this enhances the radiation from accelerating charge (Larmor) effect you describe. But your fundamental, high level description in terms of energy shuttling is great! $\endgroup$ – WetSavannaAnimal Mar 14 '15 at 3:04
  • $\begingroup$ I don't really understand your answer. Also, I once got told that infraread light is heat or something like that and then later figured out that that was probably a mistake. What you're calling heat is probably really thermal energy. Heat does have a meaning but a very complex one.Infrared light and heat are probably not the same thing either. Infrared light is electromagnetic radiation in a certain range of frequencies travelling at the speed of light in a vacumm and nearly the speed of light in air. Thermal energy on the other hand is the kinetic energy of the vibrating atoms. Candles $\endgroup$ – Timothy Mar 19 at 22:49
  • $\begingroup$ actually do produce thermal energy. I can feel a hot stream of air right above the candle flame. Objects can heat up by absorbing thermal energy or by absorbing visible light. $\endgroup$ – Timothy Mar 19 at 22:52

protected by Qmechanic Dec 27 '17 at 20:43

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