Is energy an entity?

  • #1
Summary:
There are many mathematical expressions for energy, and many more expressions for what it can do. We know what all the particles are and can describe them as an entities by concrete terms such as mass and properties. But it does not seem that we can do that with energy.
Can energy be defined as an entity? The ability to do work is abstract, so is E=mc^2. It seems like energy is a catch-all phrase for something we can only describe in terms of other physical realities.
 

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  • #3
martinbn
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Why do you ask about energy? Why don't you ask about, say momentum? Is momentum an entity?
 
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  • #4
Demystifier
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It seems like energy is a catch-all phrase for something we can only describe in terms of other physical realities.
That's correct. Energy is not an entity, it's a property. Very much like momentum, as @martinbn suggested.
 
  • #6
That's correct. Energy is not an entity, it's a property. Very much like momentum, as @martinbn suggested.
I’m grateful to know I am not alone. Thank you!
 
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  • #7
Dale
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Summary:: There are many mathematical expressions for energy, and many more expressions for what it can do. We know what all the particles are and can describe them as an entities by concrete terms such as mass and properties. But it does not seem that we can do that with energy.

Can energy be defined as an entity?
Sure. Just define “entity” in a way that deliberately includes energy.
 
  • #9
hmmm27
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Happens all the time : if my house requires 100M BTU's to get through the winter, it's not important contextually if it comes from electricity, natural gas, oil, or solar.
 
  • #12
Dale
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Deliberately?
It would be pretty ironic if I had accidentally used the word “deliberately”
 
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  • #15
haushofer
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An "entity" reminds me of "If there's something strange -- in your neighbourhood -- who you gonna call -- ..."
 
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  • #16
PeroK
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An "entity" reminds me of "If there's something strange -- in your neighbourhood -- who you gonna call -- ..."
Physics Forums?
 
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  • #17
Dale
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What did you mean?
I mean that “entity” is not a standard scientific term, and often the scientific meaning of a word is different from the non-scientific meaning (eg field). So you are free to change the definition of “entity” to suit your goals.
 
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  • #19
PeroK
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##T## is time.
 
  • #21
PeroK
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Interesting. Where did this unit come from?
It's always been there. E.g. kinetic energy is ##\frac 1 2 mv^2##.
 
  • #22
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Interesting. Where did this unit come from?
It's not a unit, it's the dimensions of whatever units you choose to describe energy. For a somewhat more intuitive example: An area has dimensions of ##L^2##, whether you're measuring the area in acres, hectares, squares (used for roof shingles in North America), square meters, square feet, barns (used in high-energy physics), or whatever.

You can find the dimensions of energy by looking at how we calculate the energy in a given situation: for example, the definition of kinetic energy is ##mv^2/2##, the dimensions of a velocity are ##L/T##, and that should get you there.

Googling for "dimensional analysis" will tell you more, and the wikipedia page is not bad: https://en.wikipedia.org/wiki/Dimensional_analysis
 
  • #23
Thank you very much!
 

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