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Offline homertyson

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What is energy?
« on: 08/03/2013 04:29:03 »
Everyone knows that everything is run by energy and comes in many forms such as electrical energy to power lightbulbs but what is the true pure form of energy. Even the human body runs on energy, from when you do exercise to the most simple thought uses energy, so does this make us energy beings as all is energy?

And if we are energy beings then our conciousness is cumulated energy so as proven by science that energy cant be created nor destroyed but can be converted into another form of energy then an afterlife exists in this form.

But the first question remains, What is energy?


 

Offline Minerva

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Re: What is energy?
« Reply #1 on: 09/03/2013 13:03:26 »
Well I cant really answer your question first question but I am a bit baffled as to how you come to the conclusion that requiring energy to exist is proof of an afterlife.

Consciousness arises as a result of the energy used in transmitting signals between neurons so consciousness requires energy to exist.  Once that energy goes so does consciousness.  You seem to be suggesting that consciousness can be stored in the energy that runs it and so although its converted into something else, that consciousness still exists in a different form of energy.  Consciousness is an emergent property of the physical workings of the brain - it requires an energised human brain in a living human body (or animal body) in order to exist.
« Last Edit: 09/03/2013 13:30:40 by Minerva »
 

Offline cheryl j

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Re: What is energy?
« Reply #2 on: 11/03/2013 18:05:37 »
Since the various elements of the periodic table were forged in the centers of stars, you and all of your atom's are the "afterlife" of a dead star.

The problem with afterlife discussions, is what most people seek is not just the continued existence of their energy or matter, but of their personality, their memory, and the ongoing experience of sensation, perception, consciousness.

 

Offline distimpson

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Re: What is energy?
« Reply #3 on: 16/03/2013 01:17:13 »
good subject and discussion homertyson. "what is energy?" is one of those simple yet profound questions, like "what is time, space?".

have to agree with Minerva on consciousness. as we define and know it, consciousness requires a physical matrix like a brain or possibly an electronic matrix (the droids are coming). If energy associated with consciousness persisted after life it would be difficult (for me) to see it as anything like a consciousness, it would be like saying the universe is conscious.

also like cheryl j dead star "afterlife" of atoms, got me thinking. not so much an energy signature after life but an entropy signature, i.e., history. everything we do perturbs a tiny part of the universe which then persists for some period of time, also after life. Not a consciousness, just a perturbation.

anyhoo, hope you don't mind me jumping in, interesting stuff. for the record, I am not a believer in ghosts, spirits, magic, ..., or supernatural forces in this universe. no answers, just interested.

 

Offline FunkyWorm

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Re: What is energy?
« Reply #4 on: 02/06/2013 17:40:02 »
Energy is the potential to do useful work - nothing else.
I throw that at people who talk about "energy fields", "energy lines" or any other bit of woo that uses the E-word.
 

Offline dlorde

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Re: What is energy?
« Reply #5 on: 02/06/2013 21:54:50 »
As FunkyWorm says, energy is the potential to do work; it's not 'stuff' in its own right (it's an indirectly observed quantity). The closest analogy I can think of in everyday life is 'financial value'. Everything has some value, and you can convert stuff with value into other stuff with value (e.g. you can sell a house with one value to buy a smaller house with another value and have enough left to buy a car of another value, and some hours of work from a gardener, and some gold of another value, and so-on). The difference is that financial value isn't conserved like energy, and although currency is a measure of value, it's not universal and consistent like the joule.
« Last Edit: 02/06/2013 21:58:38 by dlorde »
 

Offline Pmb

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Re: What is energy?
« Reply #6 on: 19/09/2013 03:57:56 »
Quote from: homertyson
Everyone knows that everything is run by energy…
If so then they “know” incorrectly.

In the first place everyone has a different idea of what it means to “run” in this particular way. Even then the best that one can say is that objects which run “have/possess” energy.

Quote from: homertyson
…and comes in many forms such as electrical energy to power lightbulbs..
You’re not being clear on this point. Electrical energy is used to maintain the filament of a light bulb so hot as to glow. The light bulb glows because the energy originally in the form of heat now has the form of light coming off the light. The current changed its form when it was used to heat up the wire thus resulting in the release of thermal photons.

Quote from: homertyson
… but what is the true pure form of energy.
This is a misnomer. There is no such thing as a pure form of energy.

Quote from: homertyson
And if we are energy beings then our conciousness is cumulated energy so as proven by science that energy cant be created nor destroyed but can be converted into another form of energy then an afterlife exists in this form.
You’ve a lot of that wrong. We are not energy beings. We are beings that utilize energy for many things. Consciousness is not cumulated energy either. Were do you get all these nutty ideas from?

Quote from: homertyson
But the first question remains, What is energy?
I wrote an article on this which I placed on my website at http://home.comcast.net/~peter.m.brown/mech/what_is_energy.htm
 

Offline Pmb

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Re: What is energy?
« Reply #7 on: 19/09/2013 04:06:51 »
Quote from: FunkyWorm
Energy is the potential to do useful work - nothing else.
That is a common misconception of energy. If you want a solid understanding of what enegy really is then pick up Volume I of the Feynman lectures and read

The Feynman Lectures on Physics, Vol-I, Feynman, Leighton, and Sands, Addison Wesley, (1963)(1989). See What is energy? on page 4-1 which reads
Quote
It is important to realize that in physics today, we have no knowledge of what energy is. We do not have a picture that energy comes in little blobs of a definite amount. It is not that way. However, there are formulas for calculating some numerical quantity, and we add it all together it gives “28” -  always the same number. It is an abstract thing in that it does not tell us the mechanism or the reasons for the various formulas.

See also In Newtonian Mechanics by A.P. French, The MIT Introductory Physics Series, W.W. Norton & Company Press, (1971) pages 367-368
Quote
Of all the physical concepts, that of energy is perhaps the most far-reaching. Everyone, whether a scientist or not, has an awareness of energy and what it means. Energy is what we have to pay for in order to get things done. The word itself may remain in the background, but we recognize that each gallon of gasoline, each Btu of heating gas, each kilowatt-hour of electricity, each car battery, the wherewithal for doing what we call work. We do not think in terms of paying for force, or acceleration, or momentum. Energy is the universal currency that exists in apparently countless denominations.
    The above remarks do not really define energy. No matter. It is worth recalling once more the opinion that H.A. Krammers expressed: “The most important and fruitful concepts are those to which it is impossible to attach a well-defined meaning.” The clue to the immense value of energy as a concept lies in its transformation. It is conserved – that is the point. Although we may not be able to define energy in general, that does not mean that it is only a vague, qualitative idea. We have set up quantitative measures of various specific kinds of energy: gravitational, electrical, magnetic, elastic, kinetic, and so on. And whenever a situation has arisen in which it seemed that energy disappeared, it has always been possible to recognize and define a new form of energy that permits us to save the conservation law. And conservation laws, as we remarked at the beginning of Chapter 9, represent one of the physicist’s most powerful tools for organizing his description of nature.
Please read the whole section to each of those portions rather than read the snippets that I posted and think that you understand both parts.

My objection with French here is that he gives the impression that energy "exists" whereas physics uses it merely as a bookkeeping scheme which requires no physical system.
« Last Edit: 19/09/2013 04:09:42 by Pmb »
 

Offline alancalverd

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Re: What is energy?
« Reply #8 on: 19/09/2013 15:04:27 »
Energy is one of the parameters that is conserved when things change. Momentum and angular momentum likewise.

Pmb's analogy with a bookeeping scheme is a good one. You can unravel a lot of human history by looking at financial records because many human interactions are monetarised, and cash in hand represents work that you have done and can be exchanged for work other people can do for you. Energy in physics is an even more useful concept because it can't be "printed" - though it is always devalued. But it is no more than a human construct (like money) used to predict and unravel the behaviour of the physical world.   
 

Offline Szostak

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Re: What is energy?
« Reply #9 on: 21/09/2013 19:51:29 »
Entropy, "Energy is never lost, it's always transformed." Well, if that's what they say, energy is never lost, yes, but it may be transformed into something that may not be useful enough to catalize something else, then it may be found to be lost?

I suck at phyisics, but this idea just came up. Can anyone give a statement about this?
 

Offline alancalverd

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Re: What is energy?
« Reply #10 on: 22/09/2013 07:21:04 »
That's what I meant by energy being devalued. The total energy in a closed system is conserved, but with each interaction it gets spread around, eventually ending up as evenly distributed heat - the state of maximum entropy. If there is no temperature difference between parts of a system, no further changes can occur.

You can take a very gloomy view of life by noticing that everything we do just makes the world less potentially useful. With a can of paint, you could mark a roadway, protect a ship, or produce a work of art. But once you have painted the Mona Lisa, you can't use the paint for anything else. You have increased the entropy of the universe and taken it one step closer to thermodynamic extinction. 
 

Offline Pmb

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Re: What is energy?
« Reply #11 on: 24/09/2013 13:37:55 »
Quote from: alancalverd
Pmb's analogy with a bookeeping scheme is a good one.
I'd like to take the credit but it was Feynman who gave me the idea for he wrote in the reference I gave to his Lectures. Recall where Feynman writes
Quote
It is an abstract thing in that it does not tell us the mechanism or the reasons for the various formulas.

I'm sure I heard it explained like this elsewhere too but don't recall where.

As far as energy not being the ability(capacity) to do work, I found an article online about this at http://www.loreto.unican.es/Carpeta2012/TPT(Lehrman)WorkEnergy.pdf

It seems like a nice article so far. I recommend reading it. It was published in The Physics Teacher under the title Energy is Not the Ability to do Work by Robert Lehrman, Phys. Teach. 11, 15 (1973)

This article http://scienceblog.com/16727/is-energy-the-ability-to-do-work/ agrees with me too.
« Last Edit: 24/09/2013 14:20:32 by Pmb »
 

Offline dlorde

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Re: What is energy?
« Reply #12 on: 24/09/2013 15:31:12 »
As far as energy not being the ability(capacity) to do work, I found an article online about this at http://www.loreto.unican.es/Carpeta2012/TPT(Lehrman)WorkEnergy.pdf

It seems like a nice article so far. I recommend reading it. It was published in The Physics Teacher under the title Energy is Not the Ability to do Work by Robert Lehrman, Phys. Teach. 11, 15 (1973)

This article http://scienceblog.com/16727/is-energy-the-ability-to-do-work/ agrees with me too.
Good articles, particularly Lehrman's; thanks!

I like his 'short, pithy definition': "Energy is... the ability to produce heat." As he says, "While this definition is neither elegant nor useful, at least it is true".

His even more inelegant, but perhaps more useful, definition: "Energy is a quantity having the dimensions of work, which is conserved in all interactions".

It seems it's not so much a question of energy being the capability to do work, but more of energy having the capability to do work.
 

Offline alancalverd

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Re: What is energy?
« Reply #13 on: 24/09/2013 17:22:46 »
As far as energy not being the ability(capacity) to do work, I found an article online about this at http://www.loreto.unican.es/Carpeta2012/TPT(Lehrman)WorkEnergy.pdf

A nicely written article indeed, but a bit confusing when he shows the mass balance of nuclear fission including the "mass of photons produced". Having convinced your students that photons do not have mass (indeed cannot as they travel at c) you could end up with egg on face or a lot of explaining to do here! Far better, I think, to stick to his previous equation of energy balance, where you add up a lot of things that can be measured (kinetic energy of fission products, rest masses of fission products, total photon energy) and show that if you multiply the "lost" rest mass by c^2, the equation balances. 
 

Offline Pmb

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Re: What is energy?
« Reply #14 on: 24/09/2013 17:27:34 »
It seems it's not so much a question of energy being the capability to do work, but more of energy having the capability to do work.
I disagree. The problem with that statement is that it can't act as a definition because it doesn't tell you how to obtain any quantity to be called "energy." What about a particle which is moving in the +x direction along the x-axis and another in the opposite direction along a collision course. When the collide there are instances when two quantities are conserved. At other times there is only one. Let's assume that is the case. We're talking about a pure inellastic collision.

If we use the ability to do work then what are we talking about? What about those two particles actions make it have the ability to do work? In one formula its the first order of the velocity times the mass that makes it conserved. In the other formula is the velocity squared times mass that is conserved. So which one is energy? Nothing about this tells us that. Why can't I call p = mv the "energy" of the particle? (and please don't tell me that its because this is momentum. We're assuming that we're starting from scratch and don't know these things yet). Why can't we call E = (1/2)mv^2 the "momentum" of the particle?

He has better examples but I can't find them. From your comment I think you missed it.
 

Offline Pmb

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Re: What is energy?
« Reply #15 on: 24/09/2013 17:51:38 »
Quote from: alancalverd
A nicely written article indeed, but a bit confusing when he shows the mass balance of nuclear fission including the "mass of photons produced". Having convinced your students that photons do not have mass (indeed cannot as they travel at c) you could end up with egg on face or a lot of explaining to do here!
I myself would never tell a student that photons don't have mass. I'd only tell them that their proper mass was zero. Not all relativity teachers teach it like that. I’m reading The Road to Reality by Roger Penrose and he uses this definition of mass too. See my article at http://arxiv.org/abs/0709.0687
 

Offline dlorde

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Re: What is energy?
« Reply #16 on: 24/09/2013 19:18:40 »
It seems it's not so much a question of energy being the capability to do work, but more of energy having the capability to do work.
I disagree. The problem with that statement is that it can't act as a definition because it doesn't tell you how to obtain any quantity to be called "energy."
It wasn't intended to be a definition, it was supposed to be a wry comment on the definition. Ho-hum, back to the drawing board...
 

Offline alancalverd

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Re: What is energy?
« Reply #17 on: 24/09/2013 23:15:00 »
Why can't I call p = mv the "energy" of the particle? (and please don't tell me that its because this is momentum. We're assuming that we're starting from scratch and don't know these things yet). Why can't we call E = (1/2)mv^2 the "momentum" of the particle?

Quite simply, because I don't. The purpose of language is to communicate, and we do this best if everybody uses the same definition of each word.
 

Offline Pmb

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Re: What is energy?
« Reply #18 on: 24/09/2013 23:44:28 »
Why can't I call p = mv the "energy" of the particle? (and please don't tell me that its because this is momentum. We're assuming that we're starting from scratch and don't know these things yet). Why can't we call E = (1/2)mv^2 the "momentum" of the particle?

Quite simply, because I don't. The purpose of language is to communicate, and we do this best if everybody uses the same definition of each word.
Please go back and read the entire post. Especially where I wrote
Quote
(and please don't tell me that its because this is momentum. We're assuming that we're starting from scratch and don't know these things yet).
That means that it was a question about principle and not practive. A hypothetical question about a world of science where the terms energy and momentum have not yet been defined.
 

Offline alancalverd

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Re: What is energy?
« Reply #19 on: 25/09/2013 06:48:26 »
There is no scientific principle involved in the naming of quantities. You don't even need to name these two, as long as you discover that the sums of mv and mv^2/2 are conserved in a closed system, and note that m is a scalar (or whatever you want to call it) and v is a vector (likewise). It just makes life easier in physics and engineering to name your discoveries consistently as quantities, although naming the "zero sum products" may be less important to a mathematician.
 

Offline Pmb

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Re: What is energy?
« Reply #20 on: 25/09/2013 17:21:32 »
Quote from: alancalverd
There is no scientific principle involved in the naming of quantities.
I believe that this has gotten off track. My purpose was to demonstrate that quantities which have momentum and quantities which have energy both have the ability to do work and therefore "the ability to do work" doesn't uniquely define energy. That is one of the reasons it can't be used to define energy.
 

Offline alancalverd

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Re: What is energy?
« Reply #21 on: 26/09/2013 00:22:38 »
I agree with your conclusion - almost. It's a fatuous definition.

However, whilst anything that has mass and velocity has the ability to do work, a coiled spring and a charged battery also have the ability to do work, unrelated to their mass or speed. Therefore energy is always the ability to do work, and anything that has momentum also has energy, but the converse is not necessarily true. 

And by the way, both energy and momentum are conserved in a pure inelastic collision. In the example you gave (#14), the system momentum was zero before and afterwards, and inelastic collisions of macroscopic bodies result in an increase in temperature of the bodies. I'll leave you to work out what happens when a neutron is absorbed by a nucleus!
 

Offline Pmb

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Re: What is energy?
« Reply #22 on: 26/09/2013 02:14:47 »
Quote from: alancalverd
However, whilst anything that has mass and velocity has the ability to do work, a coiled spring and a charged battery also have the ability to do work, unrelated to their mass or speed. Therefore energy is always the ability to do work, and anything that has momentum also has energy, but the converse is not necessarily true.
I knew this when I came up with that example. The so-called “definition” energy is the ability to do work is flawed in other ways since there are instances where there is no ability to do work yet there is energy present. Consider a neutron. It has rest energy due to its proper mass. However by itself it does not have the ability to do work when its at rest. This is example when the definition of “ability to do work” won’t work.
 

Offline alancalverd

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Re: What is energy?
« Reply #23 on: 26/09/2013 07:23:04 »
But when your stationary neutron decays, the sum of the pion and proton masses is less than the rest mass of the proton and they have kinetic energy equal to the mass difference. The same as a spring, sort of, and a radium nucleus even more so.

However your underlying point remains true, as does my preferred definition: energy is one of the conserved quantities in a closed system. This may beg the question of "what is a closed system?" where the obvious answer is "one in which energy and momentum are conserved" but if we add "and entropy increases" it's a fairly complete definition that allows us to solve all the physics equations. 
 

Offline Pmb

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Re: What is energy?
« Reply #24 on: 26/09/2013 10:03:07 »
Quote from: alancalverd
But when your stationary neutron decays, the sum of the pion and proton masses is less than the rest mass of the proton and they have kinetic energy equal to the mass difference.
I blame it on fatigue but I didn't mean neutron but meant neutrino for just this reason. Or even zero-point energy etc.
 

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Re: What is energy?
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