SPATIAL SENSE Seasons

WORD ATTACK  Earth’s tilt  axis of rotation  orbit  phases  revolution  reflection

BIG IDEAS  Describe the yearly revolution of Earth around the sun and compare Earth’s position during each season.  Explain that Earth’s axis is tilted relative to its yearly orbit around the sun.  Investigate the relationship between the amount of heat absorbed and the angle to the light source.

VOCABULARY  ellipse - a regular oval shape  revolution - motion in orbit around a center  reflection -  orbit - the curved path of an object around a star, planet, or moon  rotation - rotating around an axis

Earth’s Orbit  Like all planets in our solar system, the Earth is in an elliptical (almost circular) orbit around our Sun.  The difference between Earth’s farthest and closest point from the sun is very small.

Earth’s Axis  The Earth is rotating around on its rotational axis.  The Earth’s axis is tipped over about 23.5° from vertical.  The Earth’s North Pole points towards the star Polaris.

ONE YEAR  It takes roughly 365 days for the Earth to go around the Sun once.  Earth is rushing through space around the Sun at a rate of about 67,000 miles per hour.  The time it takes for the Earth to go around the Sun one full time is one year.

WHAT CAUSES THE SEASONS?  The combined effects of the Earth’s orbital motion and the tilt of its rotation axis result in the seasons.  Interactive Animation Interactive Animation

What makes summer hot? Concentratied heat energy from the sun heating up the surface of the Earth.

What else makes summer hot? Very little shadows blocking the sun’s heat energy.

WE REALLY DO GET MORE ENERGY FROM THE SUN IN THE SUMMER. THIS HEATS US UP. WE RECEIVE LESS ENERGY FROM THE SUN IN THE WINTER WHICH COOLS US DOWN. THE SUN IS HIGHER IN THE SKY IN THE SUMMER AND SHINES DOWN ON US FOR A LONGER PART OF THE DAY.

THE POWER OF THE SUN  At sunrise the energy from the sun reaches us in a very indirect way. The sun is very low in the sky, near the horizon where the sky seems to touch the Earth. Shadows are very long. In the winter, the sun is always low in the sky. The winter sun’s indirect light has very little heating effect upon us. Also the sun can be in the sky for as little as nine hours. In the summer the sun climbs to a very high position, so that for many hours its light is striking us very directly. In the summer the sun is also in the sky for as much as 15 hours.

THE POWER OF THE SUN

NORTHERN HEMISPHERE SEASONS SummerWinter

OPPOSITE HEMISPHERE SEASONS

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