What determines the length of daylight and why, when it’s winter in one hemisphere, it’s summer in the other?
As we know, Earth makes a complete revolution around the Sun in 365 days and 6 hours. During this time, the distance between them varies from 142 million km to 151 million km. Meanwhile, each hemisphere of our planet alternately moves closer to this huge hot star, and then summer comes to the countries located in it, while winter comes to the countries in the other hemisphere. (Find out how Australians call our summer: summer or winter?)
It might seem that the lack of warmth is due to distance. But no. It’s a bit more complicated. The thing is that Earth rotates not only around the Sun but also around its own axis, which is tilted relative to its orbital path at an angle of about 23°. This causes varying lengths of daylight. If it weren’t for this tilt, day, and night would be equal in length anywhere on our planet, and during the day, the Sun would always be at its zenith. This doesn’t happen because in winter, the tilt of Earth’s axis moves the planet’s surface away, making the daylight hours shorter. Therefore, sunlight simply doesn’t have enough time to warm up the earth, and the air temperature drops.
You can conduct an experiment: hold your palm near a desk lamp without touching it, then start rotating your hand, changing the angle at which the lamp’s radiation falls on your palm. You’ll notice that when your palm is parallel to the lamp, it heats up much faster than when it’s tilted. The same happens with Earth: in summer, when the daylight is longer and the Sun is higher above the horizon, it warms the Earth more strongly, which in turn heats the air, and we feel warm.
