What is Energy? - Unpacking Hard Definitions

[I Like Pi]

What is Energy? - Hard energy definitions

Explain this definition: energy is the ability to impart vis viva (mv²) Is it a well definition?

Here's a more complex definition: energy is that measure of the physical change of a system that is conserved as a result of temporal displacement symmetry. Explain your interpretation of this definition

I'm a bit lost as to what these definitions mean

What is vis viva?


**I think that the what the second one means is that energy is the measure of the change of the system that is conserved as a result of time travel?

 

[tiny-tim]

Hi I Like Pi!

I'm a bit lost as to what these definitions mean

What is vis viva?

**I think that the what the second one means is that energy is the measure of the change of the system that is conserved as a result of time travel?

"vis" means force, and "vis viva" is "living force" (as opposed to "vis insita", which is "innate force", or inertia).

For some details, see http://en.wikipedia.org/wiki/Vis_viva"

"temporal displacement symmetry" means that space-time, and physics generally, looks the same now as it did a thousand years ago and as it will tomorrow … a displacement in time makes no difference, so physics has time-displacement symmetry

(this is connected with Noether's theorem)

 

[I Like Pi]

Hi I Like Pi! "vis" means force, and "vis viva" is "living force" (as opposed to "vis insita", which is "innate force", or inertia).

For some details, see http://en.wikipedia.org/wiki/Vis_viva"

"temporal displacement symmetry" means that space-time, and physics generally, looks the same now as it did a thousand years ago and as it will tomorrow … a displacement in time makes no difference, so physics has time-displacement symmetry

(this is connected with Noether's theorem)

Hey tiny-tim!

Thanks for the reply! so does the definition "energy is the ability to impart vis viva (mv2);" work? like what does it directly mean? I don't think the definition is right, though I'm not sure why

EDIT: wait, i think this is wrong because that would mean that energy is equivalent to momentum x speed. and momentum is derived from energy?

and for the second one? energy is that measure of the physical change of a system that is conserved as a result of temporal displacement symmetry. I don't seem to understand this... If the displacement in time doesn't make a difference, then how can there be a physical change of the system? Aw man, i think i confused myself...

Thanks tim, you're a lifesaver

EDIT: wait, if the space-time remains the same/temporal displacement symmetry... that means that that there is a conservation of energy, and the amount of energy yesterday is the same as today, and tomorrow, etc. this results into energy being the measure of the physical change of a system that is conserved.. <-- though i don't understand that last part

 

[tiny-tim]

Hey tiny-tim!

Thanks for the reply! so does the definition "energy is the ability to impart vis viva (mv2);" work? and what does it directly mean? I don't think definition is right, though I'm not sure why

I dunno, I never did that sort of course.

Is this from a history-of-science course?

Anyway, those wikipedia articles should be some help.

and for the second one? energy is that measure of the physical change of a system that is conserved as a result of temporal displacement symmetry. I don't seem to understand this... If the displacement in time doesn't make a difference, then how can there be a physical change of the system? Aw man, i think i confused myself...

Thanks tim, you're a lifesaver

EDIT: wait, if the space-time remains the same/temporal displacement symmetry... that means that that there is a conservation of energy, and the amount of energy yesterday is the same as today, and tomorrow, etc. this results into energy being the measure of the physical change of a system that is conserved.. <-- though i don't understand that last part

Have you covered Noether's theorem in your course?

 

[I Like Pi]

I dunno, I never did that sort of course.

Is this from a history-of-science course?

Anyway, those wikipedia articles should be some help.


Have you covered Noether's theorem in your course?

No, it's a physics course, though we are studying implications and how real energy definitions are. And no, but I will check it out, maybe it'll help. Thanks so much!