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1st law of thermodynamics

  1. Sep 26, 2005 #1
    If matter and energy can be neither created or distroyed, how then does this law explain birth or growth. When a baby is born new matter is created. When a human or animal grows new cells are created, and once again more matter is created. Does this law only have to do with physical things and not biological things?
  2. jcsd
  3. Sep 26, 2005 #2
    No cell is created from nothing ! Why do you think you have to eat and drink to survive ?
  4. Sep 26, 2005 #3
    It has to do with all things in general. because although matter and energy can be neither created nor distroyed, it is just tranfered from one form to anouther like when organic matter is burnt or when a space shuttle is blasting off from earth, its all just transfer of energy.
  5. Sep 26, 2005 #4
    Got it. Ok I see it now, when a plant dies it release energy from decomposition, the compost is mineral rich and supplies new plants with energy, energy is then used to create more cells in a plant. Got it. One question, since the population is rising does that mean that plant life will always deplete and eventually run out? Does that mean that we can never have an abundance of plant life?
    Last edited: Sep 26, 2005
  6. Sep 26, 2005 #5
    Plants take energy from the sun with the chlorophyll that they have inside of them (makes them look green). What they take from the soil is certain chemicals required for them to grow. The initial energy required for a seed to start growing comes from stored food in the seed (if this is the manner of reproduction of the plant).

    I don't understand the rest of what you are saying.
  7. Sep 26, 2005 #6


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    blt93932, humans grow the vast majority of food we eat. We are not in any way "depleting" natural plant life by eating.
  8. Sep 26, 2005 #7
    however if we continue to remove plants for various reason such as food and lumber faster than we can replace them we will eventually deplete our land
  9. Sep 26, 2005 #8

    Chi Meson

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    True but that is not a stipulation of the law of conservation of energy. Ultimately, as long as the sun shines, enough energy will be provided to the earth for us humans to perpetuate our wasteful and destructive habits.

    Most of our fertile land is lost to development rather than overfarming. If we do run out of good soil, hydroponics and bioengineering will become the norm. I shudder to think what my great grand kids will be eating.
  10. Sep 26, 2005 #9
    So basically the sun will keep giving us enough energy that will become matter for awhile. It is basically impossible to deplete ourselves here on earth because of the sun.
  11. Sep 26, 2005 #10
    well im not much of a biology man but the suns energy its self doenst become matter, the plant uses photosynthesis to harness the energy from the sun and convert carbon dioxide and water into oxygen and sugars. keep in mind the amount of water and carbon dioxide the plant absorbs will be the same mass as the out put do to the law of conservation of mass as chi meson stated
  12. Sep 26, 2005 #11


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    No, energy-mass conversion takes place in nuclear reactions.


    That explains exactly what happens in the photosynthesis process for example.
  13. Sep 27, 2005 #12


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    Also, since E=mc2, energy and matter are sort of the same thing.

    Not necessarily, the 1st Law says that energy/matter is just conserved. Humans can "deplete" themselves by changing too much of something into something else that we can't use. Luckily, like a previous post said, humans are smart, and would rapidly develop new technologies to supplement this loss of something, or just get it some other way.
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