What is energy fundamentally?

[The thinker]

Do we know what energy "is"?

Hi everyone,

According to what I have read a string is a minute amount of vibrating energy. Is the word "energy" here used as an approximate for the lay reader?

I was led to this thought because if the vibration of strings make up matter and energy then what's the difference between the "macro energy" produced by vibration and the "pure" non vibrating energy?

Basically I'm asking, what is energy?

Thanks!

 

[Topher925]

Energy is the potential to do work.

 

[The thinker]

Energy is the potential to do work.

That doesn't really answer what energy is though just what it does.

I can't imagine a string of "potential to do work"

 

[kenewbie]

Energy is the sum of a calculation, not a tangible thing.

k

 

[The thinker]

Energy is the sum of a calculation, not a tangible thing.

k

Thats what I used to think, but don't they say that a photon is a packet of energy?

And like I said before how can an intangible thing take the form of a string?

 

[russ_watters]

A photon has energy. It isn't energy itself. Energy is not a "thing". You're looking for a deeper meaning where none is necessary.

 

[vanesch]

Thats what I used to think, but don't they say that a photon is a packet of energy?

And like I said before how can an intangible thing take the form of a string?

It doesn't. All this is figurative talk. As Russ said, you can eventually say that a string HAS energy (or momentum or mass, or whatever other quantifiable property). The only thing that IS energy is a quantity in a calculation.

To give you an analogy: is a bank "interest rate" ?

 

[jtbell]

Better: Is a bank money?

 

[vanesch]

Better: Is a bank money?

I was going to say that first, but money also has a tangible representation (paper money, or gold bars, or...), so this was not sufficiently abstract...

 

[The thinker]

hahaha, that's what I used to think until I started reading about string theory and QM which confused me into thinking energy was physical.

So now I have two other questions:

If there is no such thing as pure energy then what is a string?

And what was so revolutionary about E=mc^2 if E is not a real thing?

Thanks again!

 

[russ_watters]

E=mc^2 was revolutionary because no one had connected matter and energy in that way before.

 

[derek.basler]

well when you think about it, energy is primarily mass. Mass is like frozen energy. It really makes you think, what exactly is energy. But when a string vibrates, it gets energy, energy converts into mass.