SOURCE OF ENERGY is a term used to describe any form of energy that can be harnessed and used to power machines, vehicles, and other forms of technology. The most common sources of energy are the ATOM, the SUN, and petroleum fields. The ATOM is the smallest unit of matter and can be split to release energy in the form of nuclear energy. The SUN is a star that emits energy in the form of light and heat, which can be converted into electricity. Petroleum fields are areas where oil and gas are extracted from the ground and used to generate energy.