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What is life

  1. Oct 31, 2003 #1
    How can we ultimately differentiate between life and inanimate entities? Other than the obvious like reproduction and cells. Once, or if, it is differentiated should life be viewed with respect to the inanimate or the inanimate with respect to life?
  2. jcsd
  3. Oct 31, 2003 #2
    I don't know if reproduction is "obvious". Take for example a mule. It can't reproduce, but it is definately alive.

    A definition of life is one of those things that the scientists have never agreed upon.

    Good question.

  4. Oct 31, 2003 #3
    this is an interesting question... and my first intuition for it would be to describe life in terms of complexity. now i dont know much on this (i am planning to make complexity theory my summer reading) but could life be described in terms of complexity?

    The problem with this of course is that we may never be able to draw a line as to what is and is not life. (just as we may never be able to draw an acurate line on what is consious and what is not, this could also be a matter of complexity).

    But what you COULD say is that anything deemed to be of biological nature is life, and all those things which are not are non life. so the boundary would be where physics meets biology. maybe (this is very rough)[?]
  5. Nov 1, 2003 #4
    Re: Re: what is life

    It can't reproduce, but it's cells can.

    Anyway, you were correct in saying...

    ...and to that I add that philosophers haven't come any closer to it than scientists, since, in philosophy, you still have to question whether anything is alive at all ITFP. If you don't have a working definition, what right do you have to call anything "alive", or to even imply that the word "alive" has meaning? Well, that's the philosophical problem anyway.
  6. Nov 5, 2003 #5
    In my view, it is impossible to exclude anything from being alive. This is based on the fact that what the common labelling of life has no solid foundation and has more of an intuitive meaning. I sort of agree with Dark on this in that life is a measure of complexity. However, it seems to me that nothing can have infinite simplicity so everything then must be alive. There is one exception though, and that could be the smallest unit of complexity, planck's constant. Since it is indivisible and no form of energy can exist below it there must be absolutely no structure or form to the constant.
  7. Nov 5, 2003 #6
    But, if everything is alive, then everything should reproduce and be responsive to it's environment. As it is, not everything meets these two criteria.

    Now, I'm not saying that everything that does meet these two criteria is definitely alive, merely that anything that doesn't is definitely not.
  8. Nov 5, 2003 #7
    Aren't all entities that exist reproduce and are adaptive to thier inviroment in some way? I mean in order for something to exist it must exist on the terms of its surroundings, i think that goes for everything. In other words, all things are changed according to thier enviroment or exterior interactions. Since life is basically what is produced out of a changing enviroment, then how can life not apply to everything? As for reproduction, all of the so called non-living entities seem to do this too. In order for an entity to exist for even an infinitesimal length of time isn't it reproduced through time?
  9. Nov 5, 2003 #8
    Well, anything that is alive has to actively respond to it's surroundings, but I suppose you could apply that to subatomic particles too (for example). Of course, a house or a chair do not meet this criterion, but things like fire and viruses do. Like I said, these are two of the limitations on things such that anything not meeting them is definitely not alive, whereas some things that aren't alive can still meet them. That's why we don't have a good definition of "living".

    BTW, there are more criteria than those that I've mentioned, but you probably already know this.

    First of all, things do not reproduce themselves along time, since it takes a certain amount of time to reproduce, and you would thus have two entities of time.

    Secondly, on the chance that someone will show that previous statement to be false, when I said "reproduce" in the original statement, I meant along space.
  10. Nov 5, 2003 #9
    Why do we have to differentiate between life and inanimate entities?

    The problem in the definition of life may be in the parameters we have set up to descibe it.

    Maybe thats why we can not find the dividing line what is alive and what is not.

    The inatimate becomes life and then dies and is inatimate again, was it ever dead?

    Maybe a simplified definition > life is just the universe and all that is in it. Lifes ability to transform itself from the most fundamental state to evolved complex life forms.
  11. Nov 5, 2003 #10
    Oh, I forgot one point that I wanted to mention earlier. FZ+ brought up in a previous thread that we first have to establish for sure that there is such a thing as life, in the first place. Life hasn't been properly defined, so we cannot distinguish completely that which is from that which isn't. So, how do we know that anything is really "alive"? If "alive" doesn't mean anything, then nothing is alive.
  12. Nov 5, 2003 #11
    I think "you know it when you see it" applies here. Crystals grow and have organic compounds. If that is considered living then stars and even galaxies are alive because they grow and go through a "life" span from birth to death. They also contain organic building blocks. But I don't think this is the intended definition.

    My question however is, why does life persist? It seems to be more of a force in this universe rather than a characteristic of an object. We've seen numerous examples of life existing in the harshest of environments, but why? To what end?
  13. Nov 6, 2003 #12

    to quote a famous and well known philosopher "don't pick it you'll only make it worse" and "if the feeling comes a long you must whip it, whip it gooood!"
  14. Nov 6, 2003 #13

    whip it good
  15. Nov 6, 2003 #14
    what an elegant statement slatiebartface
  16. Nov 6, 2003 #15
    That's the problem, we believe that we can decide what is and is not alive because of that very reasoning. And yet, we have so many things that are "borderline" living/non-living (such as viruses, current PCs, and the AIs of the future) and the decision cannot be made so simply.

    But do they reproduce themselves? Do they respond/interact actively to/with their evironment?
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