综合一区欧美国产,99国产麻豆免费精品,九九精品黄色录像,亚洲激情青青草,久久亚洲熟妇熟,中文字幕av在线播放,国产一区二区卡,九九久久国产精品,久久精品视频免费

Heat can move in one of three ways. The first isconductance. In conductance, the heat passes through something solid, such as wood or metal. This process is pretty slow.

Another way heat moves isradiation. In radiation, the heat passes directly through space in the form of photons, tiny packets of energy travelling at the speed of light. Radiation is the way that the sun's warmth reaches Earth.

Finally there'sconvection. In convection, heat warms the air. The warm air becomes less dense (and thus lighter) than the cool air around it, so it rises. Convection is the reason stars twinkle.

When air heated by convection rises, it tumbles and swirls. When light passes from the cool, dense air through the warm swirling, not-so-dense air and back again, it gets bent this way and that. That's why the air shimmies over a fire or a radiator.

As air warmed by the earth rises through the atmosphere, it breaks into bubbles of warm air. As light from the stars passes through the bubbles, it's bent back and forth. This is what makes the stars seem to twinkle.

If there weren't any atmosphere, as on the moon, the stars would shine steadily.