Читать книгу Weather For Dummies - John D. Cox - Страница 63

Hmmm … let me see now… .

The time from the Summer solstice to the Winter solstice would be — yup, that checks out, 182 and 183 days between them, close enough.

And from the spring equinox to the autumnal equinox — oops, what’s going on here? Between March 20 and September 22 are 186 days, and between September 22 and March 20 are 179 days.

Sure enough, it has to do with the elliptical shape of Earth’s orbit around the Sun (refer to Figure 3-6). This is gravity at work — the pull of the mass of the Sun on the Earth. When the Earth is closer to the Sun, the pull of gravity is stronger. Because it is farther from the Sun from March 20 to September 22, Earth travels more slowly during that loop of its orbit.

This means that summers are seven days longer in the Northern Hemisphere than in the Southern Hemisphere. Do they know this in Australia? Is this legal?

The sunlight’s angle affects its intensity in another way. The more directly the Sun is over your head, the less of Earth’s atmosphere it has to penetrate. Various things in the atmosphere filter out or scatter some of the incoming rays, so the more atmosphere it has to travel through, the more filtering and scattering takes place. (Chapter 15 says a lot about these optical effects.)