Is energy just change that is quantified

[cosmic onion]

Apologies in advance. I am on page 1 of physics. My question is simple. Can I replace the word 'energy' with the word 'change' . Is energy simply 'change that has been quantified'.

Take 2 cases.

Case 1 -A boy bounces a ball and the ball changes shape and bounces through a window breaking glass and making noise which wiggles the small bones in someones ear.

Case 2 - A meteor strikes the Earth causing air in front to compress and heat and compresses ground in impact causing explosion etc.

The question is how many more balls would a boy have to bounce to create the same change as a meteor striking the earth.

To answer this we introduce the idea of energy. Which is just a way to quantify change. We can say an object has energy by virtue of its mass and it's velocity. Which is just it's propensity to create change.

Is this line of general reasoning correct ? Is this the way I should be thinking about energy. Is this the way others think about it ?

Please note I know the mathematical derivations for basic Newtonian mechanics. I'm just trying to go beyond the maths (hope that doesn'the sound pretentious).

 

[FactChecker]

That is not a very good definition. One that is preferred is "energy is the ability to do work, and work is moving something against a force". That definition covers a lot of possibilities, including potential energy, chemical energy, kinetic energy, etc.

Some problems with your definition:
1) If things are changing, what "has" energy?
2) If a spring is compressed, but not doing anything, what can you say about its energy?

 

[cosmic onion]

Thank you for the reply

Could you not then say 'moving something against a force' is creating a change in a system ?

 

[cosmic onion]

1 - the object that is changing has the energy
2 - the spring has a propensity to change , potential energy.

Apologies not used to coversing in physics -Hope I don't come across as rude ? If I do its due to ignorance and not malice.

 

[Dale]

Can I replace the word 'energy' with the word 'change' .

No. Change isn't conserved, energy is.

I am on page 1 of physics.

Since you are on page 1, please continue on to page 2 rather than trying to write the sequel. The rest of the book is quite fascinating!

 

[cosmic onion]

Change isn't conserved energy is , my , I have to think about that one. Maybe I have tendency to over think. This could be why I might still on page 1 Thanks for reply.

 

[FactChecker]

I applaud your effort to give a single description to something like energy, that has so many forms. But the devil is in the details.

1 - the object that is changing has the energy

If you push a car up a hill, who has energy? You or the car? Who is gaining or losing energy and why?

2 - the spring has a propensity to change , potential energy.

"potential" is a key word. A compressed spring has potential energy because it has the ability to move something against a force. "against a force" is another part that your definition does not include.

Apologies not used to coversing in physics -Hope I don't come across as rude ? If I do its due to ignorance and not malice.

Your question is a good one. You should take a moment to understand how the accepted definition has advantages over the one you propose. I think that the accepted definition is near genius. It consolidates so many apparently different concepts into one called "energy".

 

[cosmic onion]

Learning is like waiting for your ear to pop so you can hear better. At the very least I am in the happy position of knowing my ear has still to pop. I will think about what you have said and will reply if it adds value.

Thanks

 

[mishima]

Energy transfer is heat or work. That might be thought of as change, but its more useful to consider it from the viewpoint of the isolated system, where the quantity is constant (not changing, conserved).

Energy itself definitely isn't change, its just a measure of the ability to do work. It answers the question "If I tried to extract the maximum number of joules from this system in useful work, what value would that be?"

Further, not all change is energy related at all. For example, a tick in time from 1 to 2 seconds is a change that has nothing to do with energy.

 

[cosmic onion]

Thanks.

I have some real interesting things to think about from your responses.
I need to think about what you have said.

I think it's useful and worthwhile for me to think about these things as they will I presume underpin the rest of physics.

 

[Vanadium 50]

I think it's useful and worthwhile for me to think about these things

Thinking about why energy is important and how it is used is worthwhile. Making up your own definitions and theories is not.

 

[cosmic onion]

Eek. Looks like I still have lots to learn. I though physics was about coming up with your own definitions and theories and giving the world an opportunity to debunk them. Of course if the whole of the rest of the population disagreed with you and you still insisted you were right then that would simply be a sign of madness.

I think I have enough responses in this thread to allow me to move onto page 2 of my physics book.

Thanks for all the great responses.

 

[phinds]

I though physics was about coming up with your own definitions and theories and giving the world an opportunity to debunk them.

Terrible idea and absolutely not allowed here on PF (read the rules about personal theories)

 

[cosmic onion]

But wasnt all of physics at one time just personal theories till proven and then accepted ? Maybe I'm going about physics the wrong way. I suppose it makes sense otherwise PF would spend all its time debunking when time could be better spent answering real questions. I will have read of the rules.

Thanks for the heads up.

 

[rumborak]

For the most part, physics is about learning what some really smart people have figured out before you. One of the worst, yet common, mistakes by people is to assume that their armchair musings are the first time somebody ever thought about the subject.

Regarding the OP subject, I have thought about this myself many times before, and the best I can come up with is actually somewhat close to the mathematical description we have as our best right now: energy is a number in the framework that describes our universe.

 

[rootone]

people is to assume that their armchair musings are the first time somebody ever thought about the subject.

I was once convinced that this was just a trait of people born with the Sun in the sign of Libra.
Err, sorry. /jk

 

[cosmic onion]

I never presume I'm the first person to think of anything. But it is the first time I have thought about this.

Forum is excellent.

The best thing I have learned so far is that I still have lots to learn.

 

[cosmic onion]

Had time to think this over. I have found a quote from an eminent physicist that I am happy with regarding energy. Russian physicist Lev Okun says ' the more basic a physical notion is the more difficult it is to describe in words . For energy the best we can do is say IT IS THE CAPACITY TO CAUSE MOVEMENT. '