Earth Rotates On A Tilted Axis And Orbits The Sun
Nerd: How much do you know about how the earth rotates on a tilted axis and orbits the sun?
Saurav: I know a lot; where should I start. The Earth’s gravity pulls objects to the middle of the Earth. When the Earth turns, so do you. But luckily we still keep the same position. Only the view on top of our head changes. When Earth rotates, it rotates on an imaginary line going through the middle which is called an axis of rotation. The ends of the axis’ are at the north pole and the south pole. Wherever you are on Earth the surface moves from west to east as the Earth turns.
Nerd: You know a lot do you know how it affects day and night?
Saurav: Yes, I know how it affects day and night. Once in a day about half the Earth is dark. As Earth turns on its axis every 24 hours, the places where it is dark then becomes the place which has light. When a place has sunlight it is daytime there and when it is dark it is night-time. When a place is in the middle of sunlight it is probably noon. You know how there is night and midnight? Probably do know; when it is night it is in darkness and when it is midnight it is in the middle of the unlit sunlight.
Nerd: Very good. Do you know how the tilted axis and orbit causes seasons?
Saurav: This is getting easier and easier.
When Earth moves it doesn’t move in a straight line. It moves sideways, kind of like a right angle to the Sun’s direction. Without the Sun’s pull, our Earth would be going in a straight line into space somewhere. Earth’s orbit is 300 million kilometers (200,000,000 mi) across. For Earth to rotate on its axis it takes one day. In astronomy, a revolution is when one object goes around another object. The word can also mean to go around once. Earth’s rotation and orbit don’t line up. Earth rotates at about 23 degrees angle, or tilt, from this lined- up position. Earth’s orbit isn’t in a perfect circle because nothing’s perfect. In January, Earth is about five million kilometers closer to the Sun than it is in July. In January the Earth is 148,000,000 km and in July it is 153,000,000 km. It’s kind of surprising that distance doesn’t matter a lot. The combination of our Earth’s motion around the Sun with the tilt of the Earth’s axis does cause important changes to the temperature.
Nerd: Do you know anything about seasons?
Saurav: Obviously that’s the easiest questions you have ever asked. A season is a pattern of temperature changes and trends in the year. Near the equator, the temperature doesn’t change a lot like in the poles, but it has small changes. The temperatures change through the year because of the sunlight in each location. The changes are due to the tilt of the Earth’s axis. An equinox is when there is the same amount of sunlight in both the northern and southern hemispheres. When the Earth moves it comes across something called a solstice. During a solstice one hemisphere has maximum amount of sunlight and then the other hemisphere has the minimum amount of sunlight.
Nerd: You can join our science nerd club.
Saurav: It’s just basic science.
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