What is "energy"?

Discussion in 'General Science & Technology' started by Fifteendaysofbliss, Aug 17, 2009.

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  1. Fifteendaysofbliss Registered Member

    How can energy actually be defined? Since it does not consist of anything, what is it in actuality?

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  3. James R Just this guy, you know? Staff Member

    The initial definition of energy that most physics students encounter is that energy is the capacity to do useful work. It is a property of an object or group of objects (a system). The precisely-defined concept is useful because of a particular observed truth about nature - the law of conservation of energy. That law states that energy cannot be created or destroyed, although it can be transformed from one form to another. So, if a system has a certain energy before some physical change then it will, under certain general conditions, have the same energy after the change, and that fact can be used to calculate other properties of the system after the change.
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  5. Fraggle Rocker Staff Member

    This is an anthropocentric perspective on the universe, or anyway an Earth-warm-blooded-animal-centric view. When studying the universe around us we give the highest priority to information gathered by our visual sense, and in general we see only matter. So you regard anything that is not matter--anything you can't see--as "not anything."

    This is ironic since the visual signals that your retinas actually receive consist of energy (electromagnetic energy), as do the sonic signals your ears receive (kinetic energy), and some of the signals received by your other sense organs such as your heat sensors (a different part of the electromagnetic energy spectrum) and your semicircular canals that give you balance (gravity energy). I'll leave it to someone else to explain the sense that urges you to breathe by detecting an increased concentration of carbon dioxide in your blood.

    The only sense that actually senses matter directly is your sense of touch. The reality of your surroundings, as you perceive them, is 99% energy.

    Besides, as Einstein taught us, the difference between matter and energy is somewhat arbitrary. Under the proper conditions they can change into one another. Our species did not evolve in an environment where these conditions occur, so we did not develop senses that can perceive this phenomenon.

    In any case energy is just as "real" as matter. In fact both are merely different patterns of bosons. Or some such sub-sub-atomic particle; I'm no physicist.
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  7. baftan ******* Valued Senior Member

    One of the definitions of Energy is Activity: Potential or kinetic, in the form of photon or mass; energy signifies the acting regime of universal existence. If E=mc2, matter is nothing but a form of energy, so activity (energy) consist of everything.
  8. ElectricFetus I'm just going for a walk... Valued Senior Member

    When I think of energy I think of pebbles bouncing on a road as you drive along. All matter moves as such at an atomic level, bouncing, spinning, flipping, etc, as the temperature goes down the slower the matter moves, at zero Kalvin it does not move at all. This motion can also be stored irrelevant to motion driven by temperature. Atoms can store this motion by bonding to each other (or in in some cases by escaping those bonds) or by changing the nature of those bonds. When we burn something stored motion is released and the product molecules jump violently around at thousands of degrees. When we run an engine stored motion is released by the burning of fuel, those molecules push against the walls, drive a piston up and provide work.
  9. granpa Registered Senior Member

    energy is simply a conserved quantity of physical systems
  10. steponit Registered Senior Member

    we use the word energize quite commonly, but not conversely "matterize". In a closed universal system, if two mass are set apart, arent their respective masses increased, (matterized), since we imparted an energy to the system by separating them
  11. Startraveler Registered Senior Member

    This is a little sloppy. Energy is equivalent to mass, which is a similarly mysterious concept--the original poster's question wouldn't be very different if it were phrased "How can mass actually be defined? Since it does not consist of anything, what is it in actuality? " Both are properties in some sense, one determined by factors like relative position or relative motion, the other usually by some initial endowment. Both are conceptual tools to explain mathematical relationships that hold in nature--as such they provide verifiable quantitative predictions and give us some conceptual feel for what's going on (even if we don't "really" know what, if anything, is going on behind the mathematical processes we've mapped out).

    Anyway, you'll generally encounter definitions of energy that help to situate it in the conceptual and mathematical frameworks in which it is useful. As far as I can tell, it's a statement about the bookkeeping processes that play out in the universe--a mathematical device. It's not clear to me that it physically (you know, in the sense meaning something akin to "tangible"--obviously it's intimately connected to features of the physical universe) is anything.
  12. John Connellan Registered loser Valued Senior Member

    Is there a more precise definition of energy that you can provide?
  13. Rav Valued Senior Member

    This is the most enlightened perspective I have encountered for a while. I've always had a problem with some people on these forums "correcting" posts on the basis that some ideas concerning the nature of space, or energy, don't exactly conform with their respective definitions within an existing mathematical or theoretical framework. The problem of course is that some of these established definitions, as you have alluded to yourself, don't often provide a comprehensive or satisfying description of reality.

    Some people, it seems, would like people to speak where science speaks, and remain silent where science is silent. But this is completely backwards. Of course we should strive to understand the validity of what has been discovered already, but when science can only tell us part of the story, we should be enthusiastically exchanging all manner of interesting ideas in order to allow it to progress. Sometimes working within an existing mathematical framework leads us to new discoveries, but occasionally a great discovery can begin with a logically reasoned out idea that seemed absurd at first but was later integrated when it was found to have merit.

    If you listen to some of the great scientists throughout history speak freely and plainly on matters of reality, they all tend to share one thing in common. They are great thinkers. They aren't afraid to think well beyond the realm of established science. This is in contrast to many others who while having an impressive grasp of some of the more complex disciplines, seem at the same time trapped within them.

    Just to be clear, I hate crackpot pseudo science as much as the next person. There is a difference between being overly attached to an idea just because it is your own, or arguing a point endlessly because you've jumped into the deep end when you can't swim, and engaging in spirited discussion that seeks to build on what has already been established. It is the latter than I am advocating.
  14. jmpet Valued Senior Member

    Energy is surface tension in 4D.
  15. noodler Banned Banned

    Energy is the remainder, when all the action is accounted for.
  16. Bizza Registered Senior Member

    I believe Energy is mere dynamics and the rate of work an object emmits relative to another object, either within a closed or open system.

    Everything is dynamic (energized) and nothing is static (still).

    I don't believe that energy is transformable into so called "matter", nor vice-versa.
  17. Dredd Dredd Registered Senior Member

    Most descriptions are what it does or the like, not what it is.

    Like "what is intelligence", the effects intelligence has or what it does is usually set forth, because really we don't have enough knowledge to say what it is.

    We have plenty of words to say what it does, and how to use it though.
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