The Meaning of Energy? Core Physics Principle Explained by Parth G

Energy is an extremely important concept in all of physics. It is used everywhere to describe how different systems will behave. But what exactly is energy in the first place? What is the meaning of energy?

This difficult-to-answer question can be thought of in terms of a few different explanations. The one I prefer is that energy is a mathematical concept used to describe how different systems behave and phenomena occur. We can think of it as a mathematical quantity that we assign to anything relevant in what we are studying. Then, energy transfers (i.e. from one form to another, or from one place to another) occur in such a way that they obey the Law of Conservation of Energy. This allows us to predict how our system will behave over time.

Although we are talking about assigning energy values to different parts of our system, this does not mean we can randomly assign any energy values. These energy values are carefully calculated to be consistent with how everything around us seems to behave. An object with a specific mass moving at a certain speed, for example, will have a very specific value of kinetic energy based on its mass and speed.

Based on all experiments we've done so far, the Law of Conservation of Energy seems to hold extremely well. Therefore, we can use it to make predictions about energy transfers in our system, as well as how these will affect different parts of our system. And it's very interesting that the system can be very tiny, or it can be as large as our whole universe.

Another way to think about energy is that it is a physical property that objects have. For example, a moving car HAS kinetic energy (rather than the energy being a mathematically assigned quantity). This is a perfectly reasonable way to look at it, but if left unclear it can lead to some misconceptions. For example, it is easy to think based on this description that energy is some "stuff" that can flow from one object to another, almost like a fluid. And indeed, a long time ago scientists thought of heat (a form of energy flow) as a fluid. However energy itself is not a fluid, and does not have form in and of itself, like other "stuff" does. It can be thought of as "flowing" from one object to another, or transferring to a different type of energy (e.g. gravitational potential energy being transferred to kinetic energy as an object falls to Earth).

Finally, a common definition of energy is that it is the ability to do work (force x distance). But often, wordy definitions of work are stated in terms of energy. So this can lead to a circular argument, and if you are not fully comfortable with at least one of these terms then these definitions are of no help.

At the end of the day though, the reason the concept of energy is so useful is because of the conservation law. Energy cannot be created or destroyed, only transferred from one place to another, or from one type to another. It almost doesn't matter what energy is.

In this video, we also discuss how some forms of energy (e.g. potential energy) seem like a bit of a fudge to make the math work out. "Stored energy" that allows stuff to happen in the future, can easily seem like something's gone wrong. However this shows the problem with thinking about potential energy as "stored energy", or as "stuff". Additionally, all objects that we've ever studied so far seem to behave consistently with each other in terms of potential energy. The fact is, this energy value that we assign to objects exactly predicts how they will behave if a given amount of potential energy is lost - in all systems!

Some interesting reads (even though I don't agree with everything in them):
https://www.researchgate.net/publicat...
https://science.sciencemag.org/conten...
https://en.wikipedia.org/wiki/Energy

Many of you have asked about the stuff I use to make my videos, so I'm posting some affiliate links here! I make a small commission if you make a purchase through these links.
A Quantum Physics Book I Enjoy: https://amzn.to/3sxLlgL
My camera (Sony A6400): https://amzn.to/2SjZzWq
ND Filter: https://amzn.to/3qoGwHk
Microphone and Stand (Fifine): https://amzn.to/2OwyWvt
Gorillapod Tripod: https://amzn.to/3wQ0L2Q

Thanks so much for watching - please do check out my socials here:
Instagram - @parthvlogs
Patreon - patreon.com/parthg
Music Chanel - Parth G's Shenanigans
Merch - https://parth-gs-merch-stand.creator-...

Timestamps:
0:00 - Energy: A Very Central Concept to Physics
0:35 - A Useful Mathematical Concept to Assign to the System, and Making Predictions With It
1:47 - Can We Assign Any Random Energy Value?
2:54 - The Law of Conservation of Energy: Constant Total Energy
4:16 - Energy as a Property vs. Energy as a Mathematical Concept
4:48 - Misconceptions of Energy as "Stuff"
5:36 - Potential Energy: A Fudge?
7:30 - Energy as the Ability to Do Work
8:20 - Overview