I’m no expert, but I was an aerospace engineering student once upon a time. So here’s my take:

Energy is not “manmade” because it would still exist and be transferred between systems even if humans didn’t exist.

Stars would still burn. Gravity would still pull. Inertia would still inert. Accelerating mass would still require energy. There just wouldn’t be anyone around to punch in numbers into a calculator and name the concept “energy”.

Of course all math and physics are “manmade” insofar as they are theorized, discovered, and proven by humans. But these concepts would still exist regardless of humanity. This feels analogous to asking if “electricity” is manmade. We discovered and named the physical concept; it doesn’t mean we invented it.

You can say that about all of math and science. It’s all language to describe observations of the universe.

What else are you going to do?

Small aside: From this perspective ‘conservatipn of energy’ is a redundant statement. Of course energy must be conserved or else the equations are wrong. The definition of energy is it’s conservation.

That’s circular reasoning on your part. “The definition of energy is its conservation” is false so that’s not redundant. Don’t know where you got that from.

Energy is not really manmade. It’s not a physical object, but that doesn’t mean that we invented it. It’s a pattern of behavior that we gave a name to. Whether we notice the pattern or not, the pattern is still there.

It’s the same as gravity - it’s not a physical object, it’s a pattern that describes how massive objects interact. But you wouldn’t argue that gravity doesn’t exist, would you?

So, what would it be a medium of, then?

Yes, like literally all physical quantities. That’s how physics works.

I’m a layman, but it seems to me you’re conflating apples and oranges.

Money is a tool invented by humans. It only exists because we created it for our purposes. If humans never existed, money would likely not exist. And someday, money as we know it, will likely change.

Energy, on the other hand, is something that exists regardless of humans. It is a concept that does not change, regardless of how you describe it.

many have answered that as a concept, it is made up. But it is arguably the most real (and important) thing in all of physics (or maybe action, which is also some function dependent on energy). the money comparison is fine, if we have different forms of denominations of money (currency notes (different amounts), gold coins, etc) we have different forms of energy quantas.

Here is a viewpoint to understand - almost everything acts in a way to minimise total system energy. this can be (almost) made valid all the time if you include some probablistic factors. (If we take thermodynamics (which is by definition study of dynamics of energy(and heat, which can be considered as some kind of raw energy), then we include entropy, which is basically finding how many ways can a particular energy can achieved.). This is not a very rigorous way to put it all, but basically all of physics basically works on energy. Forces are basically caused by some kind of gradient in energy.

The curious thing about matter is that if you zoom in far enough, you’ll find that it is energy, and energy is basically vibrations and waves rippling.

The way it’s often described, if you zoom into a hydrogen atom, it’s mostly empty space, let’s say the proton is the size of a tennis ball, the electron is like a grain of sand a kilometer away.

But then zoom further in, inside the proton, and it’s made of three quarks. But those three quarks make up only 1% of the proton’s total mass! The other 99% is like a boiling and roiling little sea of all sorts of particles popping in and out of existence, such as gluons (which keep those three quarks bound tightly together), as well as more quarks, and other more exotic particles, some of them heavier than the proton itself! But they disappear almost at the same instant in which they are created. This is a constant, non-stop process, happening inside every proton and neutron in the universe.

And what do you call that virtual stuff that always keeps on popping in and out of existence between the three permanent (aka valance) quarks and makes up 99% of the proton’s mass? That’s energy.

Now zoom back out, and back in, towards the electron; what’s going on there? It’s a lone particle (also a wave, but let’s not get into that now), there is no 1% / 99% of something, all valance no virtual.
But nudge that particle towards its’ antimatter counterpart, the positron, and both particles dissolve into a flurry of photons that instantly fly away at the speed of light - pure energy. It’s as if their little charge shells (electron - negative, positron - positive) dissolve and a flash of pure energy comes out.
This also applies to quarks and their antiquark counterparts.

That right there, is Einstein’s E=mc^2 in action, in all its’ glory. Energy equals mass.

Energy is something. It is there, even at the most fundamental and abstract level. It can be measured precisely, and explains so much so clearly, it’s incredible.

EDIT: fixed a sentence in the wrong place

Surprisingly good question, i would say. “yes” and “no”

Yes, physics specifically looks out to find “conserved quantities” and then goes on to ascribe great value to them, so, in some sense, yes, energy is considered important because it is a conserved quantity.

Also, yes, there are different types of energy (mechanical energy, light energy, chemical energy), and summing them all up via “energy” is indeed a bit of an accounting trick. but it’s also a so fundamentally useful trick that we consider it “real”.

Also, different than money, there is no central bank that can cause an arbitrary amount and cause an enormous inflation overnight. Similar to wood or cereals, there just is a limited supply of it per year, and that’s what we can use. Physics makes the rules here.

People have died from energy. So, no.

You could die from nuclear radiation, micro waves, electricity, heat. These are all energy.

Our concept of energy is man-made by way of our incomplete ideas and finite understanding of the universe. However the actual thing we attempt to describe is real.

Energy and its counterpart information are universal abstractions with many physical representations. They show up in many different context and under different reference frames.

So scientist, academics, mathematicians, who hyperspecialize into a certain domain of knowledge, understand energy as it appears indifferent context. They like to call the same generalized phenomenon different names.

Energy and information show up whenever you look. Encoded in a swinging pendulum, the electron cloud vibrating around atoms, the wavelength quanta and redshifting of photons, the nuclear fusion and fission of elements in stars.

Biological process of plant cell chloroplast, photon solar energy, carbon and water to churn sugar and protien. Dynamics of all living things based on complex calculative statistics relating food, resources, population size, and death rate.

Electrical whizzing of neurons that make up the computations of biological minds. Lakes of water floating above head forming the convection cycle. Virtual particles that pop into and out of existence in the smallest scales of existence at high fractions the speed of light.

Immense gravitational waves that emminate from two black holes merging their topologies. Infinitesimal gravitational pulls that relate you to the sun moon, planets, every comet, speck of dust, everything in the observable universe.

These are all real observable things that exist whether or not we attempt to describe or sense them. Energy and information are everywhere because they make up everything.

Yes it’s manmade concept because people are made from matter so they use energy as a matter representation ignoring everything else that doesn’t have matter. Looking at you SI. 1 Joule = 1 J = 1 kg⋅m2⋅s−2 is amount of work done when a force of one newton displaces a body through a distance of one metre in the direction of that force. S you can see you need a weight, a distance and a time. Given that in quantum world distance is infinite, time and weight is 0 it’s completly manmade product.

It’s as made up as time, but it’s as real as anything can be understood to be, with emphasis on ‘understood’. It doesn’t exist in actuality mostly because our words and models don’t describe it even close to well enough to consider the actual thing. It’s like a really poor translation of a word, it might get us closer to understanding what’s going on but will never be if your goal is to describe it to something like the human mind.

If it can predict what will happen it is real