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YOU and I already know a great deal about the Earth ,because it is the place on which we live. The Earth
is a " PLANET" that is ,an almost spherical ball a rock, soil, and water, surrounded by an envelope of gases which we call " AIR"or the "ATMOSPHERE".
The shape of the Eirth is more correctly called an "OBLATESPHEROID" which
is a complicated way of saying that the planet is slightly flattened at the " NORTH" and " SOUTH POLES" and bulges slightly at the "EQUATOR". This modification of the spherical shape occurs as a result of the Earths rotation about an axis through the poles. As the Earth spins, its materials tend to be forced outwades. This force is grater at the equator than at the poles.
The Earth, together wite its twin planet, or satellite, the MOON, are suspended in space and move in an "ORBIT" around the fieryball of the sun at the reat of one complete circuit every year -to be exact every 3651/4 days. It is because this period of rotation is not exctly 365 days that evry four year -we need to have a LEAP YEAR of 366 days. This makes up for the quarter days lost in the normal 365 day year.
We have said that the material of the planet tend to be flung outwards as the Earth goes round. Whenyou look at the ground beneath nyour feet or take hold of a piece of rock in a quarry it is hard to imagine that the shape of a piece of plasticine.But it is simply a question of the scale of thinges. The Earth seems to us to be very hard and solid because we are so tiny by comparison. But the forces locked up within the planet are more than a match for the strenth of the rocks. It has been said that if we could reduce the Earth to the size of a football and its hardness by an equivalent amout it would have a consistency something like that like that of
toothpaste.
It is up Perhapes you have heard the expression" spaceship Earth". You can understand that if you were isolated in a tiny spaceship for the rest of your life it would be very important to make the best use of all your resources and not foul the compartment with your waste. This is also true of the Earth, but because it is so big we sometimestend to forget it.
al
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Published: February 29, 2008