e. The combined hason The twenty four hour period of daylight at the poles is also called Accu 2. Indicate whether the following statements are true or false. a. The circle of illumination is the imaginary circle that separates day from night b. 20 March is also known as the winter equinox. c. During the December solstice, the Sun's rays shine on the Tropic of Cancer d. The rotation of the Earth influences the ocean currents. 26
Answers
Answer:We have seasons because Earth's axis – the imaginary line that goes through the Earth and around which the Earth spins — is tilted. It's tilted about 23.5 degrees relative to our plane of orbit (the ecliptic) around the Sun. As we orbit our Sun, our axis always points to the same fixed location in space. Our northern axis points almost directly toward Polaris, the North Star.
Earth Orbits Our Sun
This picture shows Earth from its side as it orbits our Sun. The axis is tilted and points to the North Star no matter where Earth is in its orbit. Because of this, the distribution of the Sun's rays changes. In June, in the northern hemisphere summer, the Sun's rays — and warmth — reach all the way to the north pole. In December, in the northern hemisphere winter, the north pole is tilted away from the incoming sunshine.
The “fixed” tilt means that, during our orbit around our Sun each year, different parts of Earth receive sunlight for different lengths of time. It also means that the angle at which sunlight strikes different parts of Earth's surface changes through the year. Sunlight striking the surface at an angle is “spread” across a wider area compared to sunlight striking perpendicular to Earth's surface. Areas that receive more scattered sunlight receive less energy from our Sun. All of these factors combine to give Earth its annual cycle of seasons!
Sun's Rays
For part of our orbit the northern half of Earth is tilted toward the Sun. This is summer in the northern hemisphere; there are longer periods of daylight, the Sun is higher in the sky, and the Sun's rays strike the surface more directly, giving us warmer temperatures. The north pole is in constant daylight!
When the northern half of Earth is tilted toward the Sun, the southern hemisphere is tilted away. People in the southern hemisphere experience the shorter day lengths and colder temperatures of winter.
During winter in the northern hemisphere, our northern axis continues to point to the North Star, but, because we have moved in our orbit around the Sun, our northern hemisphere now points away from our Sun. The north pole is completely dark and other places in the northern hemisphere experience the shorter day lengths and colder temperatures of winter as the Sun traces a lower arc across the southern sky and the Sun's rays strike the surface at a lower angle. When it is winter in the northern half of Earth, the southern hemisphere, tilted toward our Sun, has summer.
During fall and spring, some locations on Earth experience similar, milder, conditions. Earth has moved to a position in its orbit where its axis is more or less perpendicular to the incoming rays of the Sun. The durations of daylight and darkness are more equally distributed across all latitudes of the globe.
What doesn't cause the seasons?
The seasons are not caused by how far Earth is from our Sun. Earth's orbit around our Sun has a slightly elliptical path (very slight!), and the Sun is not exactly in the center of the ellipse. This means that, during the year, Earth is sometimes farther from our Sun, and sometimes closer — but the difference is small (not so for some other planets!). Earth is closest to our Sun in January (perihelion) and the farthest away in July (Earth is 147.5 million kilometers from the Sun when it reaches aphelion). If distance were the most important factor, the entire Earth would have summer in January when we are closest to our Sun and winter in July when we are
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