Why do we have seasons? Well it all has to do with the tilt of the Earth's axis. If you live near the equator then you're used to virtually no seasonal changes. You're experiencing summer all year long. If you live at one of the Poles, then you get two very long seasons: The sun stays up all summer, and stays down all winter. If you live anywhere else, you get to experience 4 seasons. The earth orbits around the sun once a year and is tilted about 23.5 degrees. When the top of the earth is pointed toward the sun, then it's summer in the northern hemisphere – when the sun rises highest in the sky and the days are the longest- leading to the solstice (or longest day of the year). As the earth moves along the orbit the days begin to get shorter. A quarter of the way around the orbit, Fall sets in, with the Fall equinox, a day where daytime and nighttime are equal. The earth continues along, with the days shortening until reaching the Winter Solstice (longest night of the year) at this point in the orbit the northern hemisphere points away from the sun. The earth continues along this orbit with the nights shortening and the days lengthening. About ¼ of the way (to summer) we reach the Spring equinox, again where the day and night are the same length, but this time the days are strengthening. We continue along, the days getting longer, the sun climbing higher and higher in the sky, until the summer solstice.
Try this: Using a washable marker or masking tape, make a big oval on the floor. Take a lamp and remove the shade, placing the lamp in the center of the elliptical. Take an orange and cover it in aluminum foil. Take the aluminum orange and stab a straw or stick all the way through (you can use a protractor to measure the 23 degrees for older kids). Now. In a darkened room. Stand next to the light. (which can be on the table or floor). Hold the orange from the top and bottom, so the stick/straw still points at an angle (not up and down). Now slowly walk the elliptical orbit around the sun, at the point furthest from the sun, where the northern hemisphere tilts toward the sun – this is the Summer Solstice. Continuing on, to the exact opposite side, where the northern hemisphere tilts away from the sun, marks the Winter Solstice. You can see how bright the light is against the top of the orange during the summer and how dark it is there in the winter. Coincidentally, on the other ½ way marks of the oval (between the solstices) is the equinox, when day and night are equal!
If the summer solstice is the day we receive the most sunshine (in the northern hemisphere) and the winter solstice is the day we receive the least, then why are they the start of the next season, rather than the peak of that season?
Well this is why it's often referred to as the Mid-Summer Solstice, rather than the beginning of the summer solstice. True it's recognized as the start of summer. This is because of the Oceans. It takes a bit of time for them to heat up In the summer and cool in the winter. By the end of June (the summer solstice) they are still pretty cool from the previous winter, and that delays the peak of the air heating until about a month to a month & a half later. (as all that cool water keeps the air cooler as well, in the same way an old ice-box worked. Have a piece or two of ice and it kept the whole box or room cool). Similarly, in December, the water is still holding warmth from the summer, and the coldest days are sill a month or so ahead. (on average anyway!)
What About The Distance From The Sun? The number one mistake people make is believing the seasons are due to the rotation of the earth around the sun, bringing the earth closer at some points and further at others. While this is one contributing factor, in actuality it's the point of the earth. The earth circles around the sun, it's true, but it really isn't a circle, it's more of an oval. The distance from the sun actually varies as the sun doesn't sit in the middle of our invisible elliptical around it. The elliptical is really set off center, so that we're much closer to the sun at one end of the elliptical than at the other.....which season do you think we're closest to the sun? You're probably wrong, it's WINTER! That's right, we're actually closest to the sun around January 3-5 (which is why we have our brightest moon in the end of December)
I've also got a TON of resources at my blog - http://kickbuttcrazylapbooks.blogspot.com/search?q=solar+system
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