Few scientists agree altogether with this idea of Heat Death for the universe, but the two laws of thermodynamics are considered the most important scientific laws of all. The basic unit used to measure energy is now called the joule. One joule is roughly the energy needed to lift an apple one metre off the ground. Energy chains Energy can neither be created nor destroyed, so all the energy in the universe has been around since the dawn of time. This means that when you turn on an electric fire you are using energy that has always existed and always will.
Energy can change form again and again.
The heat energy of the fire can be traced back through a series of conversions to light from the Sun. There are similar chains of conversions for every bit of energy in the universe, stretching right back in time. The Sun's energy is absorbed by the leaves of plants living millions of years ago. When they die, the plants are slowly buried deeper and deeper 2. The plants are squeezed into coal by the weight of rock above, concentrating the energy.