Heating the Earth

The Earth is heated by the Electromagnetic Radiation the Sun emits. The Earth is not heated uniformly, however. For example, the Equator gets more direct radiation from the sun than the poles all times of the year, and so the poles are cooler. The tilt of the Earth leads one hemisphere to get more radiation than the other, and is responsible for the seasons.  When parts of the earth are heated by the Sun, that heat is transferred by conduction and convection to other areas of the Earth. This redistribution of heat is what is responsible for the wind and ocean currents.

Wind

The land heats up and cools down faster than the oceans. Warmer air has a lower density and it rises. During the day the hotter air over land rises up and is replaced by cooler air from the ocean creating a sea breeze. At night, the land is cools much more quickly than the water. The cooler air over the land moves to the ocean where warmer air is rising up. This is a land breeze. The arctic poles are much colder than the Equator and the hot and cold air circulate around the globe.

Coriolis Effect

When air or water travels directly north or south towards the equator, the solid part of Earth is rotating below it. Because water and air are fluid, they do not rotate in the same way as the solid parts of Earth. If the Earth was not spinning and a projectile was launched south by someone at the North pole, it would end up at the same longitude when it got to the Equator. However, the Earth does spin. By the time the projectile got to the equator, the Earth would have rotated beneath it, and it would appear that the projectile has veered off to its right to someone who was standing stationary on Earth.  That is the Coriolis Effect. If this is done in the Southern Hemisphere, the object will appear to veer to the left to a stationary observer. This effect is more pronounced with greater times and distances.

Ocean Currents

Wind creates surface ocean currents. It determines their direction along with the Coriolis Effect and the shape of the land masses the currents flow past.

Experiment

Investigate the differences between heating the polar ice caps and land not covered by snow.

Earlier we had discussed heat created by exposure to visible light. The most intense output of electromagnetic radiation from the sun is in the visible light range. Black objects absorb more heat than white objects which reflect more visible light. The poles are colder because they get less direct radiation from the sun and they reflect more light. The land absorbs more radiation from the sun and it is warmer.

In this experiment I had the kids go outside in the sun and sit under a white blanket and then a black one and tell me which one was hotter to sit under. We took note of which blanket each child sat under first in case they just got hot from being under the blanket.

You must give the kids a break between sitting under each type of blanket, otherwise they will just say the last one they sat under is warmer, no matter which one it is. If any of the kids say the white blanket is warmer, go through reasons that it could be the case. I had 3 kids sit under together for time reasons. Some of the reasons could be sitting closer to classmates, stretching out more or less, or not being completely covered by the blanket. We discussed some ideas from our lesson on how animals keep warm.