Airy disk brilliance (the brightness of a point-source stellar image) is proportional to the fourth power of aperture.
艾里斑的亮度(点光源恒星的图像亮度)正比于孔径尺寸的四次方。
2
And so, when you think about how much cement concrete are consumed annually on the planet, this becomes a considerable pointsource of greenhouse gas emissions.
当你想到，在地球上每年要消耗多少的水泥混凝土的时候，这将是温室气体排放的，一个主要来源。
3
How to regulate "non-pointsource" pollution, such as pesticides from agricultural run-off, is a continuing, and harder, debate.