Energy is ability to do work, and work is moving something against a force. It is measurable in Joules (J, the most known unit), British thermal unit (Btu, the amount of heat needed to raise by one degree Fahrenheit the temperature of a pound of water). This article deals with all energies used since the beginning of life. It is said that the oldest energy is fire but with the advent of the Industrial Revolution, the use of fossil fuels began growing as much as the number of industries that were set up. Nuclear power has been used as an energy source only since fifty years, so most of fossil energies has been used and will disapeared.
But other problems are generated : in the past century, it became obvious that the consumption of non-renewable energy sources is causing more environmental damage than any other human activity. These fossil fuels are causing problems such as ozone depletion and global warming. This website article was published in 2007 and its information are coming from The Energy and Resources Institute (TERI in New Dehli), by Darbari Seth Block, IHC Complex and Lodhi Road.