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Course: AP®︎/College Environmental science > Unit 3
Lesson 4: Earth's seasonsSolar radiation and Earth's seasons
Review your understanding of solar radiation and Earth's seasons in this free article aligned to AP standards.
Key points
- Nearly all of Earth’s energy comes from incoming solar radiation, or insolation. The insolation reaching any one spot on Earth's surface varies according to latitude and season.
- Earth is a sphere. This means that the sun’s rays hit the different latitudes of Earth at different angles. The angle at which the sun’s rays hit the Earth determines the intensity of the solar radiation at that location.
- At latitudes near the equator (
), the Earth’s surface is almost directly perpendicular to the angle of the sun’s rays. In these regions, solar radiation is intense because the sun’s energy is concentrated over a small surface area. As a result, equatorial latitudes generally experience hot temperatures throughout the year. - At mid latitudes (
to ), the sun’s rays hit the Earth at a slant. This means that incoming solar radiation is spread over a larger surface area, and so is less intense than at equatorial latitudes. Earth’s mid latitudes generally experience seasonal warm and cool temperatures during the year. - At polar latitudes (
to ), the sun’s rays hit the Earth at even more of a slant. So, at polar latitudes, incoming solar radiation is spread over an even larger surface area, and is even less intense than at mid latitudes. In addition, the sun's rays become scattered and diffuse as they travel through the Earth’s atmosphere, and this effect increases with latitude. The polar latitudes generally experience cold temperatures throughout the year.
- The Earth's axis of rotation is tilted
from the plane of its orbit. As the Earth rotates the sun, this tilt causes seasons, which are divisions of the year that vary in temperature, weather, and the number of daylight hours. - The duration and intensity of insolation at different locations on Earth varies seasonally. A location receives its most intense radiation during summer, and its least intense radiation during winter.
- Summer occurs when a hemisphere is tilted towards the sun. This tilt causes the hemisphere to get more direct sunlight for more hours a day, and temperatures tend to be warmer. A location on Earth’s surface receives the most solar radiation on its summer solstice, which is the summer day with the longest period of daylight.
- Winter occurs when a hemisphere is tilted away from the sun. This tilt causes the hemisphere to get less direct sunlight for fewer hours a day, and temperatures tend to be cooler. A location on Earth’s surface receives the least solar radiation on its winter solstice, which is the winter day with the shortest period of daylight.
Want to join the conversation?
- Little extra fun fact: The earth orbits the Sun in an elongated ellipse, which also contributes to the intensity of the seasons(6 votes)
- According to this video (below), while the orbit is an ellipse, it actually diminishes the intensity of the season (e.g., it is furthest during Northern Hemisphere summer, i.e., hot, but less hot than would otherwise be).
https://www.khanacademy.org/science/ap-college-environmental-science/x0b0e430a38ebd23f:earth-systems-and-resources/x0b0e430a38ebd23f:earths-seasons/v/seasons-ms(4 votes)
- how would part of the planet be winter and the other be summer or spring and autumn, because that would mean that if I lived in the northern hemisphere it might be winter and then if I hopped on a plane and moved to the southern hemisphere it would be summer. how would I have either gone forward two seasons or gone back two seasons?(3 votes)
- you haven't gone forward or backward, it's just that January is warm in the southern hemisphere, so you haven't gone forward or back you have just gone to an area with different temperatures. The same way that places like California is warmer than somewhere like Canada.(5 votes)
- What if earth stop spining?(2 votes)
- Well here are my thoughts. First off, since the earth is spinning at around 1,000 mph, if we assume that it stops immediately, then it would immediately have relative motion with the atmosphere or at least, the inner air that we breath. the lower parts of the atmosphere, namely below roughly 15,000 feet will start spinning relative to us, which will generate winds up to 1,000 mph. To put that to scale, it is strong enough to ware down whole skyscrapers in a matter of minutes. And that is not to mention the fact that we will all be thrown at 1,000 mph to the direction the earth used to spin. If we were to crash into something, the energy generated per person is roughly equivalent to 1.6 tons of TNT explosive.
It is possible that only deep sea divers can survive the throw. But that is just the beginning. As time goes on, our earth, since it doesn't spin, will have its surface divided into two regions, the one facing the sun will heat up to over 200 degrees Fahrenheit (93 degrees Celsius) in a matter of days. The side facing away will drop to lower temperatures of around -70 degrees Celcius. It is most likely impossible for any macrobiotic life to survive on the hot face, but it is possible that arctic animals will soon adapt to the cold side. Humans, unfortunately, will probably not last.(3 votes)
- How many universes are there.(2 votes)
- According astrophysicist Brian Cox, there may be Aleph Null (countable infinity) number of universes, and they may or may not be the dimensions that we don't see existing in our universe. In fact, there are theories that suggests that our universe is the result of a world sheet colliding with another. A world sheet is a sort of sheet that contains Aleph Null number of universes, and there may be also an Aleph Null number of those, two in the fluctuations of movement may have collided to form our universe, the collision being the big bang.(1 vote)
- Another name for the north star is jerusalem.(0 votes)
- Because the ligts.(1 vote)
- Where does the Earths energy come from besides solar radiation and isolation?(1 vote)
- when is the winter solstice(1 vote)
- It occurs annually around December 21. The reason of why it occurs is due to the tilting of the Earth axis (Also as said in the lesson). The Winter Solstice is basically when the Earth has the maximum tilt away from the Sun. Hope this helps.(1 vote)
- how does solar radiation affect earth's seasons(1 vote)
- How do seasons occur?(0 votes)
- earths rotation and the change of distance of the earth and the sun.(1 vote)