aWhy does the cycle of seasons occur on the Earth? What is a season anyway? Examples of seasons include winter, spring, summer, and fall, but what is a season? Do seasons occur everywhere on Earth? Let's investigate how and why seasons occur so you can answer all of these questions and amaze your friends, relatives, and other graduates of Harvard university who cannot answer these questions accurately.Seasonal changes are based upon temperatures in a given location. The Earth receives its energy from the sun, and so the amount of heat we gain and the amount of heat we radiate back into space (or lose) will determine temperature.pose1 Which situation would cause temperatures in North America to remain the same (stay constant)?The amount of heat absorbed by the sun equals the amount of heat lost into space.The amount of heat absorbed is greater than the amount of heat lost into space.The amount of heat absorbed is less than the amount of heat lost into space.The motion of the sun around the ecliptic (the path the sun follows around the Earth) means that different areas of the Earth receive more heat than at other times. Your job is to discover how this process occurs. In this animation, there is a light bulb which represents the sun and a beach ball that represents the Earth. The large beach ball in the upper left hand corner shows which section of the earth is receiving the most energy (heat) from the light bulb (sun). If you choose to have the animation be a globe and not a beach ball, click on the switch button. (This is solely a matter of preference. By the way, the red dot on the globe marks the spot of the University of Utah in Salt Lake City, UT where these cool activities are produced!)

fileTestLoad.flaWhat segment of the Earth (ball) is receiving the most direct sunlight at position A?The Northern Hemisphere The Southern Hemisphere The section of the ball in the middle You would expect this location that is receiving the direct sunlight to be __________ than the opposite hemisphere.warmer colder

pose2What area of the Earth representation is receiving the most direct sunlight at position B?The Northern HemisphereThe Southern HemisphereThe section of the ball in the middleWhat do you think happened to the temperatures in the Northern Hemisphere from position A to position B?Temperature increased.Temperature decreasedTemperature remained relatively the sameWhat do you think happened to the temperatures in the Southern Hemisphere from position A to position B?Temperature increased.Temperature decreased.Temperature remained relatively the same.Look at the representation of the Earth. The line through the Earth represents the tilt of the Earth. What happened to the tilt from position A to position B?The tilt shifted from right to left.The tilt shifted from left to right.The tilt remained the same

pose3What area of the Earth representation is receiving the most direct sunlight at position C?The Northern Hemisphere The Southern Hemisphere The section of the ball in the middle What do you think happened to the temperatures in the Northern Hemisphere from position B to position C?Temperature increased.Temperature decreased.Temperature remained relatively the same.What do you think happened to the temperatures in the Southern Hemisphere from position B to position C?Temperature increased.Temperature decreased.Temperature remained relatively the same.Look at the representation of the Earth. The line through the Earth represents the tilt of the Earth. What happened to the tilt from position B to position C?The tilt shifted from right to left.The tilt shifted from left to right.The tilt remained the same.

pose4What area of the Earth representation is receiving the most direct sunlight at position D?The Northern Hemisphere (top portion of the ball) TThe Southern Hemisphere (bottom portion of the ball)The section of the ball in the middle (equatorial region) is receiving the most direct sunlight. - correct.What do you think happened to the temperatures in the Northern Hemisphere from position C to position D?Temperature increased.Temperature decreased.Temperature remained relatively the same.What do you think happened to the temperatures in the Southern Hemisphere from position C to position D?Temperature increased.Temperature decreased.Temperature remained relatively the same.Look at the representation of the Earth. The line through the Earth represents the tilt of the Earth. What happened to the tilt from position C to position D?The tilt shifted from right to left.The tilt shifted from left to right.The tilt remained the same.

So now you have investigated how different areas of the Earth receive different amounts of sunlight throughout the course of one Earth year, but how do you determine which hemisphere has a certain season at a certain time of year? Let's rework this activity with another angle!pose5Now you can move the earth around using the arrows. Try and swap to the ball or back using the symbol on the right.Reset the Earth representation to position A. The area receiving the MOST direct sunlight will be experiencing summer. What location is that?The Northern Hemisphere.The Southern Hemisphere.The equatorial regions.

What season would the Northern Hemisphere be experiencing at this point in the model?WinterSpringSummerFallWhat season would the Southern Hemisphere be experiencing at this point in the model?WinterSpringSummerFallIn position D, it is it March in the Northern Hemisphere, what month would it be in the Southern Hemisphere? (This is not a tricky question, but read it carefully!)MarchJulySeptemberDecemberIn position B, if the Northern Hemisphere is experiencing fall in September, what season is the Southern Hemisphere experiencing?WinterSpringSummerFallIn position A, if the Northern Hemisphere is experiencing summer in July, what season would the Southern Hemisphere be experiencing?WinterSpringSummerFall

Is the summer sun above the horizon longer than it is in the winter?YesNoDoes the angle (directness) of the sunlight affect the intensity of energy from the sun?YesNoThese two effects work together to cause seasons. Do you think that distance from the sun itself has anything to do with it? If so, you are sadly mistaken. Even though the Earth has an elliptical orbit, the variation in the Earth to sun distance is only about 2%, and that is not enough to make seasonal differences as large as the ones seen on Earth. In fact, the Earth is actually closest to the sun (perihelion) in the first week of January, which is winter in the Northern Hemisphere. The Earth is the largest distance from the sun (aphelion) in early July when it is summer in the Northern Hemisphere.Something else that is interesting to note is that in the polar regions, there are periods of time in which there is light reaching the Earth's surface 24 hours a day. There are also periods of time in which there is no light reaching the Earth's surface in that area for months at a time.At which position on this model does the NORTH POLE receive sunlight 24-hours a day for several months straight?Position APosition BPosition CPosition DWhat is happening at the SOUTH POLE at the same time?Sunlight is being received 24-hours per day as well.No sunlight is being received at all.There is sunlight during the night-time.None of these.At which position on this model does the NORTH POLE receive no sunlight and have darkness for months at a time?Position APosition BPosition CPosition DWhat is happening at the SOUTH POLE at the same time?Sunlight is being received 24-hours per day as well.No sunlight is being received at all.There is sunlight during the night-time.None of these.

The official beginning of each season is marked by the following Earth and sun relationships: Vernal Equinox - Vernal is the Latin word for green. Equinox comes from the Latin word meaning equal, referring to the fact that there are equal amounts of daylight and darkness. When the sun is at this position, the sun is moving northward along the elliptic.Summer Solstice - This is the point on the elliptic when the sun is furthest North. Solstice comes from the Latin word meaning stationary (not moving) and refers to the fact that the sun sort of pauses in the sky in its northern position before beginning to move southward. Autumnal Equinox - This is the opposite of the vernal equinox, when the sun is moving southward instead of northward in the sky. The day and night are of equal length.Winter Solstice - This is the point on the elliptic when the sun is furthest South. It pauses in the sky before beginning to move northward. Of course, the weather doesn't instantly change when these dates arrive on our calendars. The ground, air, and oceans take time to warm up from winter or cool down from summer. This is called thermal lag. Because of this lag time, temperatures on Earth lag behind the timing of these events by about one month.

How would seasons be different if there were no tilt to the Earth's axis? Let's see!pose6What area receives the majority of the Earth's sunlight at position A?The Northern HemisphereThe Southern HemisphereThe equatorWhat area receives the majority of the Earth's sunlight at position B?The Northern HemisphereThe Southern HemisphereThe equatorWhat area receives the majority of the Earth's sunlight at position C?The Northern HemisphereThe Southern HemisphereThe equatorWhat area receives the majority of the Earth's sunlight at position D?The Northern HemisphereThe Southern HemisphereThe equatorAt what position would the equator experience summer?All year longPositions A and CPositions B and DPosition B onlyNone of theseAt what position would the North Pole experience months of complete darkness?All year longNeverPosition CPosition DNone of theseAt what position would the South Pole experience 24-hours a day of light?All year longNeverPosition APosition BNone of theseAt what position would the Northern Hemisphere experience winter?The Northern Hemisphere would experience an intermediate season all year longThe Northern Hemisphere would never experience winterA and BNone of theseAt what position would the Southern Hemisphere experience winter?The Northern Hemisphere would experience an intermediate season all year longThe Northern Hemisphere would never experience winterA and BNone of theseThe summers in the equatorial regions would become ___________ if the Earth had no axial tilt.hottercoolerthey would stay the sameALL DONE :-)