What is energy anyway?

Two weeks ago, we talked about what we perceive as physicality in this space-time that we live in and the fact that it is mostly empty space. Even though the physicality that we experience is mostly empty space, what remains is made up of subatomic particles that are really vibrating forms of energy. So everything, in essence, is made up of energy. Before we dig into this concept any further, I thought it'd be good if we took some time to talk about "what is energy anyway?"

Energia

Over 2,000 years ago, Aristotle talked about energy or what was the Greek term, energia, as a philosophical concept that actually applied to things like happiness and pleasure as well as the physical world.

Vis Viva

As the understanding of energy evolved during the Enlightenment era and as people started doing more science in the late 17th century, Gottfried Leibniz came up with the Latin form of the term energy - "vis viva", or living force, to describe energy.

Potential or Kinetic

Of course, energy and the concepts for energy have evolved over time since then to include many forms of energy. Specifically, energies are described as either potential energy, meaning there's some ability to have energy applied to a mass to move it over a distance in some time, reaching some speed, which is kinetic energy. So, energy is described in many different ways scientifically, either as potential or kinetic, or the combination of the two forms within a system. 

E-MC²

These definitions work fine when we're operating in a cause and effect Newtonian type of universe that is perceived by our sense. However,  as we move into the relativistic universe described by Einstein, that formulation of kinetic and potential energy doesn't always pan out well and what Einstein showed us was that energy and mass are equivalent, with speed of light squared as a factor. In other words, what we perceive of as physical can also be expressed as energy.

We'll dig into this and the implications of these observations a little bit more as we move forward over the coming weeks. For now, let this soak in, and have a great week.