We think air is weightless,but actully we each have a column of air pressing down on the top of our heads with a force of 1KG per SQ cm (15 IB per SQ in) at sea level. this force is the equivalent of having 40 bags at sugar an our heads. fortunately, our bodies are designed to with stand this pressure.
WHY DO WE NEED AN ATMOSPHERE??
without the atmosphere, all the water on the earth would evaporate, and living things would not be able to exist. Temperatures on earth would be bombarded by harmful rays from the sun, such as ultraviolet light, which can cause sunburn and cancer. the earth is not the only planet to have an atmosphere, but only the earth's atmosphere can support living things. for example, the atmosphere of venus is made of carbon dioxide and the surface temperature is around 475 degree(c887 degree f).
-THE EARTH'S ATMOSPHERE-
the air around us is acually part of the earth's atmosphere. it is made of layers of gases and water vapour that surround the whole planet.the atmosphere is over 2400km (1500 miles) thick and is held in place by the earth's surface , and it prevents damaging rays and small pieces of rock from outer space reaching our planet.
-WHAT IS GLOBAL WARNING?-
some og the gases in our atmosphere, particarly carbon dioxide, trap heat given off by the earth. we are releasing increasing amounts of man made carbon dioxide from factory chimneys and car exhausts, so the atmosphere is trapping more heat than in the past and average temperatures around the world are rising by about 1 degree c every 25 years- an effect called global warning. if it contunies, eventually the polar ice caps will melt and raise sea levels
-WHEATHER AND CLIMATE-
the north pole has a very different climate from the equator, but both have stromy weather from time to time.climate is the name we give to the typical weather pattern in one place , which does not change much. weather , on the other hand , is caused by activity in the earth's atmosphere.air is always on the move; it heat up and cools down; and can became water -laden or dry . in many places, the weather is always changing, even from hour to hour and over a few miles.
WHY DOES THE WIND BLOW??
when air passes over ground warmed by the sun, it is heated and becames lighter. because the air pressure-called a low - pressure area. air is sucked into this area from surrounding areas, wheare the air is what we call the wind . the bigger the difference in pressure between the low and high-pressure areas, the stonger the wind.
WHAT ARE THE CLOUDS MADE OF??
the way clounds from is similar to the way steam is produced when water boils.warm air can hold moistere in the form of water vapour. when warm air rises and cools, any water vapour in the air turns into small water droplets (less than 0.05 mm or 1/64 in wide). if the aie temperature is below freezing, the moisture from ice crystals, the droplets or crystals from clouds. they are easily blown about in the wind , so the shape of a cloud constantly changes. the water droplets fall as rain or hail ice crystals as snow
SNOW
in freezing temperatures, moisture droplets in the clounds freeze to form snowflakes.
RAIN
water droplets in a cloud link up until they are big and heavy enough to fall to the ground as rain
water droplets in a cloud link up until they are big and heavy enough to fall to the ground as rain
No comments:
Post a Comment