We assume that nothing else has been created from nothing ever since. At first the energy was so concentrated that it's form was unlike anything we have ever seen. After some expansion of the universe the density of the energy decreased until atoms formed, maybe after 100,000 years . This illustrates two of the most important things about energy, that the total amount is fixed and that it can change its form. Today s lecture is to get us up to speed about what constitutes energy and provide us with a series of definitions.
Energy is the most important topic in today s science.
A huge amount of research effort is being put into this field . Work Work is done whenever a force is exerted over some distance. Pick up a book and raise it 1 foot. Then your muscles applied a force equal to the weight of the book over a 1-foot distance. If you were in a car accident and the fender was smashed in, then work has been done moving the metal of the fender the smashed distance.