Why do we feel the heat of the Sun

We have already discussed in the previous post that a hotter object has atoms with high kinetic energy. If this object is put in contact with a colder object, energetic atoms will start to transfer heat to atoms of colder object and this is phenomenon is known as heat conduction. But, Sun is about 100 million miles away from the earth and yet we still feel it's heat. Space between earth and sun is vacuum with no particles to conduct the heat. So, how is heat conducted 100 million miles away to earth without any heat carriers? This occur through the phenomenon known as "heat radiation". 

 Sun surface is very hot (about 6000 C) and so atoms of gases (hydrogen and helium) in Sun have very high kinetic energy. Electromagnetic radiation (heat) is emitted whenever an electric charge is accelerated. These energetic atoms have positive charge and negative charge, and constantly bumping into other atoms and thus accelerating and decelerating. So, Sun emits heat in the form of electromagnetic radiation. 

 Electromagnetic radiation do not require particles to travel and thus can travel through vacuum. This is the reason why we feel heat from the Sun. Couple of things to note is, electromagnetic radiation emission from hot objects consist of wide range of wavelengths (visible light from 400-700 nm) and general distribution of spectrum is shown below:

 Wien's Displacement Law
(Source of image: http://www.spaceflight.esa.int/impress/text/education/Glossary/Glossary_W.html)

So, higher the temperature of body, higher the intensity of energy emitted.

Follow-up questions: how can electromagnetic radiation travel through vacuum and why do accelerated charge emits electromagnetic radiation?


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