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All of you must be aware of how sensitive plants are
- they need the right amount of heat, water, and light to grow well. There are very few
plants that can grow throughout the year, but science and technology
has advanced so much that we can actually create the environment needed for a plant to grow
well.
The green house
was created for this purpose. Greenhouses are buildings with
glass or plastic roof and walls, used for cultivation and
protection of tender plants and of plants that are grown out of season.
Green houses are designed to control the balance of temperature,
moisture, and light needed to grow diverse plants all in one
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Natural sunlight is good enough for plants in the
spring, summer, and fall, but artificial light is
sometimes needed during winter. Most of the heat in the winter comes
from the sun, but steam, hot water, or hot air circulating systems can
provide extra heat.
Summer heat can be
reduced with ventilators, fans, and other methods. Humidity
is controlled mainly by checking the amount of water in the soil.
Glass is a very good material for making the greenhouse.
The Sun gives off electromagnetic energy and
these come in different types - like visible light, radio waves,
infrared waves, ultraviolet waves etc. Other than the visible light,
the other forms are quite harmful in large quantities. Glass has a good
property of allowing infra-red light to pass through,
as well as the normal visible light. The above diagram clearly shows how
a greenhouse allows energy to enter and keep the plants warm.
 On a much larger scale, we could say that
the Earth's atmosphere works on a similar principle as that of the
greenhouse. It allows infrared light from the Sun to enter, but prevents long wavelengths
to leave. The presence of gases in the air, like nitrogen, oxygen allow
both short and long wavelength infra-red (IR) light to pass through. The presence
of excess carbon dioxide in the air is a problem since it traps most of the
long wavelength IR light. With the increase of carbon dioxide gas in the air over the past
decades (due to burning coal, oil, gasoline etc.), the earth has become warmer
because infra-red light is being trapped inside the earth's atmosphere. Scientists say
that the carbon dioxide content in the air has almost doubled over the past 100
years!!
Green house Effect, is the
term given for the role the atmosphere plays in warming the earth's
surface. The incoming solar radiation is also held within the
earth's atmosphere by gases such as methane, and ozone. The high temperatures created by this greenhouse effect is predicted to
cause major disasters since they will cause the polar ice to melt, which will
increase the sea levels causing major floods. Environmentalists continue to work to
reduce the amount of gases we are introducing into the atmosphere through burning of
fuels, aerosol use etc. in the hope of saving the earth from catastrophes. We all
need to be more aware of how we can help them in this cause.
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