Question

Think I'm gonna pop a question that have been on my heart, sense I went to high school:
In chemistry, physics and biology we like to talk about the concept "energy", this made me wonder: What is energy and does energy exsist?

Answer 1

In the past 2 years I have been wondering about this question, nobody I have spoken to, have never been able to give me a definition, I could settle with. Now after have spoken with a lot of people I made the following of energy definition:

“Energy is an index number we can apply to any system on the cosmic zoom. The difference in energy from one state in time t0 to time t1 indicates the potential for the system to change.”

I like to hear people’s thoughts on this matter.

Answer 2

@blues
@ataly

Answer 3

@ebaxter01

Answer 4

My understanding is that energy can be kinetic energy - ie the fact that something is moving means that it has energy, or potential energy - like a rock at the top of a mountain that could roll down, changing the potential to kinetic energy. There's also chemical energy - I guess this could be converted into motion (kinetic energy too). I think the definition of an engine might help: this is a machine which converts chemical energy into useful motion. Heat is similar, except it's kinetic energy in a hot gas that could be used in a steam engine for example. (In a steam engine chemical energy is converted to heat, which then is used to produce motion).

To summarize, energy certainly exists. (Einstein put it in one of his equations so it must exist - it's the E in E=mc2). I like the overall definition of energy as potential for a system to change - a car to go faster thanks to the chemical energy in the fuel, or a rock to roll down a hill due to gravity.

Answer 5

I guess the definition will depend on what you want to study. If you want to study quantum/relativistic effect or the cosmos I would suggest to ask physicist ;-)
For the biology relevant part you can probably ajust your definition by mentioning the capability to perform a work (somewhat similar to @ebaxter01 argument)

Answer 6

I've talked with a physicist who teaches classical mechanics, he said that from his experience that energy was going to seen as grocery billing... that energy is just to keep track on what happens in systems.
He also pointed out that if energy exists, then energy has to be a particle found in any mass, due to Einsteins relations E=mc2 or anything with momentum.

Answer 7

However I agree with you both, and thank you for helping clearing up this matter.