2007年9月12日 · Light affects matter, like sun rays evaporating water, therefore is physical. Einstein's famous equation, E=mc 2, shows that (light) energy cannot exist without (matter) …

2015年1月3日 · Two more things: - There are several properties of light that can be termed density. Energy-momentum density (including, energy density, momentum density, energy …

2011年6月10日 · All the light you see would be from outside the evolving event horizon, but accreting matter lighting things up would make it look similar. [EDIT: Note, when two stars …

2008年4月19日 · What would happen if matter would have to cool down in other ways, than by producing EM radiations? (Someone suggested that matter would never cool down, and …

2016年7月8日 · Hello everyone, I know that pre-main sequence stars do heat up because of gravitational contraction, and the increase in internal energy (and so in temperature) comes …

2006年1月12日 · This might be a stupid question but, taking a shower yesterday, I was wondering how is light propagating through the air molecules. For example, take the light coming from a …

2023年6月22日 · the reduction in overall lighting which is needed to activate molecules so they can emit their fluorescent photons and well as; the light at twilight tends to be more red, which …

2019年10月21日 · Although AC itself, as you have correctly observed, has no polarity, the direction of current flow, especially in a non-isolated circuit (e.g. one in which neutral is …

2017年6月27日 · I think you could be right about background IR being shuttered by the moving leaves. Another idea I had was reflection from the house behind - but the house is not behind …

2014年5月26日 · Many dark colors appear black, depending upon the lighting. For example, one of my old uniform coats was "Navy blue", which looks pretty black except when in bright …