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Mass energy equivalence in a bagttery and an animal

  1. Dec 5, 2011 #1
    A charged battery should have a mass a little greater than a depleted battery. Surely that is measurable. So does a live person have greater mass than his or her dead equivalent? Surely that is a 2nd law of thermodynamics that would be revealing. Or is the entropy of life so small that it is difficult to detect?

    All good wishes,
    Dr Z
     
  2. jcsd
  3. Dec 5, 2011 #2

    gneill

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    Well let's see. A 9V lithium battery has a rated energy capacity of about 1200 mAhr (milliamp-hours). That's equivalent to about 39 kJ of energy, and by E=mc2 that's the equivalent of about 4.3 x 10-13 kg of mass. A 9V battery weighs in at about 34 grams.

    I'd say that would be pretty darned hard to detect!
     
  4. Dec 5, 2011 #3
    I got 46 grams for a ray-o-vac. What brand did you weigh?
     
  5. Dec 5, 2011 #4

    gneill

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    No deep research, just picked out a shipping weight for a lithium battery on a site that came up with a google hit. Since orders of magnitude are what matters here, I figured that a sample of one was sufficient for the purpose :smile:
     
  6. Dec 6, 2011 #5
    I guess the lithiums are lighter than the alkalines.
     
  7. Dec 6, 2011 #6

    Ryan_m_b

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    When a person dies it isn't because they've lost energy but because something has disrupted a dynamic system. Over time a human will cool though as metabolic activity is no longer warming their body, this would cause a decrease in mass.

    (Just to head off any crackpottery the myth that a human body weighs noticeably less after death due to the soul leaving is exactly that: a myth)
     
  8. Dec 6, 2011 #7
    As a pathologist, I have the notion that dead differs from alive in a fundamental sense. When a person dies, there is a period in which the muscles are flaccid, followed by a time when the breakdown of cell membranes releases calcium ions to expend the remaining ATP. This results in the "stiffening" of the body. Within four or five hours the body again relaxes. This happens when the ATP is expended. As such a dead body manifests both living and dead impressions at the time of death.

    I have a fundamental question. Take a human who dies in a very sudden manner, can the entropy of the brain be identified? If so, that entropy should be huge. Consider what it takes to power the bluebrain(IBM project to reverse engineer the human brain) surely that entropy could be deteced. What if you completely disrupt any animal, a shrimp fopr example, could not modern detectors detcect that loss of energy (think LHC style detectors) that is emanated with an animating force?


    All good wishes,

    DrZ
     
  9. Dec 7, 2011 #8

    Ryan_m_b

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    I cannot make sense of what you are saying. As a pathologist you should surely know that death occurs because something disrupts the dynamic processes that keep a body alive. There is no "animating force". The energy lost from a body comes in the form of heat, when a person dies chemical reactions pretty much cease (energy stops being released) and the energy still in the body radiates away.

    I don't know what you mean by measuring entropy; entropy is the amount of energy available to do work but it has little bearance on whether or not a system is "alive" or "dead".
     
  10. Dec 8, 2011 #9
    If by "identifying" entropy, you mean measuring the change in entropy, then that is impossible. And like Ryan said, there isn't any animating force that keeps living things going.
     
  11. Dec 8, 2011 #10

    Borek

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    Sometimes crackpot ideas make good titles to interesting movies.

    That would be either Gibbs or Helmholtz free energy.

    Not that it makes OP question in any way more reasonable.
     
  12. Dec 8, 2011 #11

    Pythagorean

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    Entropy is energy not available for work (i.e. the energy that escapes as heat, for instance).

    In the context of information theory, Friston's "Free energy principle for the brain" discusses a bit about entropy, but this is not thermodynamic entropy. The basic premise of his paper is that the job of the brain is to reduce entropy (which in this case, is the difference between predictions and reality in the Bayesian sense).

    This kind of organization would not exist in dead things that aren't processing senses. It's difficult to relate to real energy though, since these information transfer systems require hardware that is not proportionally representative of the information processing tasks (so lots of bulky, energy-sucking equipment can be used to do relatively easy processing tasks, while a simple tissue configuration may take care of more complicated tasks).
     
  13. Dec 8, 2011 #12
    I do not suggest an animating force. Let me put it this way, as far as we know, the human brain is the most complex object in this galaxy. As such, it has very very low entropy and therefore its construction required a great deal of energy. Completely disrupting a live human brain should therefore release a considerable amount of energy. How could that energy be calculated?
     
  14. Dec 8, 2011 #13

    gneill

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    Your car is considerably more complex as an ensemble than random elements scattered in the crust of the Earth, and a good deal of energy went into constructing it. Yet when it runs out of gas and "dies" there's no great flash of departing energy. All the bits that make up the car are still in place; It is simply no longer burning fuel.
     
  15. Dec 8, 2011 #14
    Yes but if you disrupt the car completely, for example you vaporize it, energy in the form of entropy is released. If you were to instantly vaporize a human brain, considerably more energy should be liberated. In some sense, the human brain is the end result of billions of years of evolution. It's not just an individual. Therefore, enormous energy was expended to create it. Vaporizing a living human brain should therefore liberate the energy of billions of years of entropy reduction/increasing complexity. Where is it? It may still be a small number but it should be detectable yes?
     
  16. Dec 8, 2011 #15

    gneill

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    Energy expended in developing a product design is not carried over into the manufacturing process, as any engineer will tell you!

    There will be a certain amount of chemical energy released by the burning of fats and so on, but you'll have to put a huge amount of energy into it in order to disrupt all the chemical bonds if you want to vaporize it. Any energy represented by the "information" held by the structure is indistinguishable from the energy held in the atomic and molecular bonds because in fact that is how it is stored. It just goes to show you how little energy is really required to store information.

    Ice is a highly organized ensemble of hydrogen and oxygen atoms. But it takes energy to disrupt it and randomize its contents (i.e. melt it). The "information" that the crystal structure of ice held is completely swamped by the magnitude of the energy in the bonds themselves.
     
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