Hi! I wonder what makes the often black "painted" aluminum heat sinks for electronics cold by the touch? To me a shiny heat sink would work better because then all the incoming wavelengths are reflected. A black heat sink would however absorb all the incoming wavelengths because that is by definition what makes it black. So if it absorbs all the incoming wavelengths it should get hotter, right? But touching an unused ordinary black heatsink gives coldness to your hands. So my empirical studies tells me that I'm wrong. We may however look at it in another perhaps more proper way. There is a "lamp" which has both shiny and black wings inside. These wings have the shiny side on one toroidal direction and the black side on the other. The whole arrangement is supported by two needles above and below the wings and the support is of almost no friction (due to glass-needle). Shining on it with a lamp light makes the arrangement rotate along what toroidal direction? I have learned and seen that it rotates with black side first. This is because the change of momentum is 2p when you shine on the shiny side and only p when you shine on the black side (which absorbes the incoming photon). Feels like I'm almost off topic, but this is all I know about black/shiny bodies. Best regards, Roger PS Is my blog really deleted because I can not seem to find it.