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Does Energy really exists or is it just made up entity (like the quantum fields) to explain things which couldn’t be explained? For example: we can’t measure energy as it is, we always calculate the difference before and after the work done. Besides no one knows where it comes from! As it can’t be created or destroyed how does it begin to exist in the FIRST PLACE?

Qmechanic
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A.M.
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    This might help - Basic energy question – mmesser314 Aug 18 '21 at 10:28
  • Possible duplicates: https://physics.stackexchange.com/q/3014/2451 , https://physics.stackexchange.com/q/19216/2451 and links therein. – Qmechanic Aug 18 '21 at 10:46
  • I suspect the answer to the first question would be the same if you asked it about mass or momentum or force for example: does momentum really exist, or is it just something made up by physics? – user253751 Aug 18 '21 at 11:56
  • The quote from Feynman in this answer (thanks for the link, @Qmechanic) is, IMO, an especially good way of saying it. TLDR; "[Energy] is a mathematical principle...a numerical quantity which does not change when something happens. It is not a description of a mechanism, or any-thing concrete..." – Solomon Slow Aug 18 '21 at 12:01
  • @user253751, You are right, it's all math, but people seem to have a harder time grasping "energy" than they do those other concepts. Maybe it's because mass and momentum are things you can feel. Energy, not so much. Maybe it's because energy has more ways to manifest itself: When you're not dealing with relativistic speeds, it's more work to show that energy was conserved in some scenario than it is to prove that mass or momentum were conserved. – Solomon Slow Aug 18 '21 at 12:17
  • @SolomonSlow We can often see energy transforming from one form to another; we can see the weight goes down as the clock runs; we can see and hear the explosions in the car engine that make the crankshaft spin; we can feel the heat from the electric heater and watch the meter spin. Sure, the energy itself is invisible, but I think if you can grasp the concept of wind (which is also an invisible flow with visible effects) then you can grasp energy flow. – user253751 Aug 19 '21 at 09:56

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There are some things that physics doesn't have an answer to at the moment. For example, why there is more matter than anti-matter. Why the masses of the particles have their values isn't known either - they are put in as parameters in the 'standard model' of particle physics.

It's also not known why the universe has its mass or why it has a certain number of particles.

Your question seems to fall into that category.

One thing that you might find interesting is that it could be argued that the total energy of the universe is zero.

For each mass $m$ the gravitational potential energy due to it, and its rest mass cancel

$$mc^2 - \frac{GMm}{R} = 0$$

Where $M$ and $R$ are the mass and radius of the universe respectively. Why this is approximately the case is known as the flatness problem, also connected to the 'Large Number Hypothesis' and is still the subject of debate.

John Hunter
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  • Do you mean that the derivative of the total energy is 0 and not the total energy? – Tachyon Aug 18 '21 at 11:30
  • @Tachyon, it meant the total energy, but could you explain what you meant please. – John Hunter Aug 18 '21 at 11:42
  • If there is a system (such as the Universe) that has total energy, then according to the law of energy conservation, then total energy should not change. On the other hand, the energies that make the total energy CAN change. Therefore, it follows that $$\frac{\mathrm{dE} }{\mathrm{d} t} = 0$$ Since the total energy is constant. If it wasn't, then it would imply that the energy is being created or destroyed from nowhere. – Tachyon Aug 18 '21 at 11:48
  • @Tachyon, Yes, so $E=0$ and $\frac{\mathrm{dE} }{\mathrm{d} t} = 0$ – John Hunter Aug 18 '21 at 12:36