4.1 SUN AND EARTH
The Sun is the star closest to Earth. It provides the light, heat, and energy for life.
Ancient peoples worshipped the Sun as a life-giving god. Some of the names given to the Sun god were Aton, Apollo, Helios, and Sol. Scientists study the Sun today. It is critical to Earth and is a key to understanding distant stars that cannot be observed in detail.
The Sun's total energy output is enormous. The Sun's luminosity L0 is 3.85 x 1026 watts. Solar energy is practically inexhaustible. The amount of the Sun's energy that falls per second on Earth's outer atmosphere, called the solar constant, is about 1400 watts/m2 (126 watts/square foot). This amount of energy provides about as much heat and light in a week as is available from all of our known reserves of oil, coal, and natural gas.
Our Sun is dynamic and seething (Figure 4.1). It is in turn extraordinarily f
Figure 4.1. Solar activity. Hot active regions on the Sun imaged by an extreme ultraviolet imaging telescope aboard European/U.S. robot Solar and Heliospheric Observatory (SOHO).
active and relatively quiet. Changes in solar energy output affect Earth's climate, atmosphere, and weather, as well as modern power-transmission and communications systems. These changes are monitored to learn exactly how the Sun affects Earth.
State three reasons why modern astronomers, physicists, and engineers are using their most sophisticated techniques to determine the true nature of the Sun.
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Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.