energy

The ability to do work on another object. Energy comes in many forms, including kinetic, potential, and thermal. It is what causes things to move and to have temperature. On Earth, we create electrical energy for our homes at power plants, we turn gasoline into energy to make our cars run, and we eat foods so that our bodies have energy to move. Plants use energy from the sun to grow, and gravitational energy causes objects to fall to the ground. In space, stars shine because of the energetic reactions that take place in their cores and galaxies form and rotate with the energy of the objects that they contain. In his famous equation E=mc^2, Einstein showed that mass and energy are equivalent. Like ice and liquid water, mass can be thought of as a solidified version of energy.