1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B How does evolution theory fit the entropy theory

  1. Sep 29, 2016 #1
    the second law of thermodynamic state that their will be more chaos, and natural selection in the opposite of that.

    maybe this is a stupid question but can somebody anser this
     
  2. jcsd
  3. Sep 29, 2016 #2

    vela

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

  4. Sep 29, 2016 #3

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2016 Award

  5. Sep 29, 2016 #4
    Thx i get it now
     
  6. Sep 29, 2016 #5
    just one more thing, they talked no energy in or out a closed system but what if i take the whole galaxy as a system? or the whole universe?
     
  7. Sep 29, 2016 #6
    The universe is a closed system. A galaxy isn't, because it is emitting light, and we can see other galaxies with telescopes. It's very hard to have a true closed system, but often we can treat something as a closed system if we can quantitatively show that the energy transfer across the border is negligible compared to what we are focused on.
     
  8. Sep 29, 2016 #7

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2016 Award

    Then when one part of the world has an decrease in entropy, another part will have an increase equal or greater in entropy.

    You don't have to use the entire universe for this. Just look at a heat engine (Carnot cycle). You can calculate how much one part has an increase in entropy and another having a decrease in entropy.

    Zz.
     
  9. Sep 30, 2016 #8

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    I recently read 'Life on the Edge' by Jim Alkjalili. In the book he suggests that evolution can only occur as a result of Quantum interactions and that the statistics will not allow it to work by thermodynamics. I know you can't just take a single source to be enough to explain something as consequential as that but he does refer to a fair number of creditable sources in the book.
    He quotes a number of biological processes that can only be explained in terms of Quantum Tunnelling and offers reasons why it does not actually require super low temperatures.
    A very good read, in any case.
     
  10. Sep 30, 2016 #9

    DrClaude

    User Avatar

    Staff: Mentor

    Sorry, but that sounds like a load of bs someone overselling their idea.


    That quantum effects are important for life as we find it, ok, I can buy that. But that does not mean that life requires quantum effects (although, at the same time, since the world is quantum, it makes sense that evolution has made use of all that is available).
     
  11. Sep 30, 2016 #10

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    I can understand your skepticism but the numbers are too important just to be dismissed. He concludes, for instance, that simple random mutation processes would take too long for a simple bacterium to evolve.
    The book is not expensive on Kindle and makes a good read.
    I think my post has more bs than that book!
     
  12. Sep 30, 2016 #11

    Bystander

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Waayyy oversold ... entropy of mixing plus entropy of very wasteful chemical reactions is more than enough to drive evolution; the intuitive equivalence of "disorder" with "the dark side of 'The FORCE' ' " confuses more than a few people.
     
  13. Sep 30, 2016 #12

    BillTre

    User Avatar
    Science Advisor

    I have been little impressed by these kinds of arguments.

    They often seem to leave a lot of things out of their calculations like:
    1) there are many copies (really big numbers if you are talking about molecules) of whatever is evolving,
    2) things (such as genes) can be duplicated and then changed to build information increases much more rapidly then doing everything "from scratch",
    3) many genes can be involved in evolving something (increasing the number of targets for mutation),
    4) evolution has not only huge time spans (millions of years) to change things, but some organisms have very short generation times (bacteria can be as short as 20 minutes; 26280 generations/year). Many iterations lets little things add up over time.
     
  14. Sep 30, 2016 #13
    I linked a vid in another thread showing bacteria mutating in real time.
     
  15. Jun 11, 2017 #14
    Sorry to come to this discussion late, but I'd like to expand on the original question. I don't buy the quantum argument, but I do think life (and computers and solved jigsaws etc) "seem" too ordered to say they took that order from the sun. My answer involves looking at the 2nd law itself.

    Summary: 2nd law is based on random state-changes, but natural selection drives state-change in another direction, so there's no reason it should satisfy the 2nd law.

    Some observations, let me know what I got right or wrong:
    • As I understand it, the 2nd law of thermodynamics is a law of statistics, not physics (and thus not really a law of thermodynamics, although it applies to it).
    • Any system that changes randomly from state to state is more likely to change to a less ordered state, simply because there's more ways to be disordered than ordered. It's only tied to the physics of our universe because our universe is such a system.
    • It seems to be overlooked that the 2nd law is explicitly based on randomly changing between states. Without this, there's no reason to presume it will go to a less ordered state. And this is the key. Natural selection is a process that directs the state-change in a different direction. It pushes uphill, to a more ordered state.
    • The standard answer to this has been given above already, that this local increase in order is balanced by a greater decrease in entropy elsewhere (the sun), but why is this necessary? 2nd law is based on random state-changes, but natural selection drives state-change in a non-random direction. Even if it only does this locally, it doesn't need to be fuelled from elsewhere, because we've broken the rules the 2nd law requires.
    • It "seems" (in quotes because I acknowledge my limitations in not knowing how to quantify this) that a living creature has a ludicrous level of order. Same for a computer, or gluing a broken mug back together, or a sorted pack of cards. Apparently if you shuffle a deck of cards well, it's extremely unlikely to match any other shuffled deck that ever existed, yet I can easily sort the cards into any order I want. I am able to defy the 2nd law, not because I've taken order from elsewhere, but because I've taken away the thing the 2nd law is based on, random state-change.
    • Is the amount of order in the sun really so much more than all the living creatures, computers, solved Rubik's cubes etc on Earth? The sun is obviously huge, but there are lots of stars, and few (presumably) places where such ordered things exist as here on Earth. There are many more ways to rearrange parts of the sun and still have a functioning sun than there are to rearrange living creatures or solved Rubik's cubes without damaging them.
    • Consider a simple system where phrases are randomly generated. Let's say we start with a very ordered phrase, like "Let's test the 2nd law!". Randomly change one character at a time. It will follow the 2nd law and become more disordered over time (a good example of how this law is a law of statistics not physics). Now add a driving force akin to natural selection to this tiny "universe", where there's a target phrase, where we only allow random state-changes where no less characters match the target phrase. It won't take long for us to reach our target phrase, with this driving force at play. We have easily defied the 2nd law in this simplified universe, without the need for the increased order being matched by decreasing order elsewhere in the system.
     
  16. Jun 11, 2017 #15
    Do you have any equations and or data to support these claims?
     
  17. Jun 11, 2017 #16

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    • Wrong
    • Partially Wrong
    • Partially Wrong
    • Wrong
    • Wrong
    • Wrong
     
  18. Jun 11, 2017 #17
    Really? Do you really disagree that the 2nd law, which explains increasing entropy, is based on the assumption of random state-change? I thought that part at least was uncontroversial. If I'm wrong, that's fine, but I'm here to understand why I'm wrong and gain a better understanding, which the replies so far haven't helped with.

    As for supporting equations or data, my basic argument isn't dependent on it. The claims about the amount of order in the sun vs. the order in life etc, IS dependent on it, which is why I presented that part in the most tentative terms. But my overall argument doesn't depend on it. See the summary I gave previously.
     
  19. Jun 11, 2017 #18
    There was a really good discussion of Maxwell's Demon somewhere on PF. I will see if I can find a link. In the meantime, https://en.wikipedia.org/wiki/Maxwell's_demon
     
  20. Jun 11, 2017 #19
    OK, thanks for the Maxwell's Demon reference, that helped. I was viewing order as "meaningful" (depends on your point of view) subsets of state-space and their ratio (or some function of it) of the total state-space. Now I see alternative definitions which tie the 2nd law specifically to energy. With that definition I'd agree, energy is conserved but the total amount of useful energy is always decreasing. The concept of increasing disorder IS a statistical law, for any meaningful measure of order, but it seems maybe entropy and the 2nd law are defining order explicitly as it relates to energy. Is that right?

    So to be clear, am I right that a solved Rubik's cube or a sorted deck of cards would have exactly the same amount of entropy as their unsolved/shuffled counterparts, as far as physics is concerned, because the amount of useful energy in either is the same?
     
  21. Jun 11, 2017 #20
    The Rubik's cube has the same number of microstates and macrostates however getting it to a specific state requires energy. The multiplicity of a solved rubik's cube is one therefore the entropy is smallest (ie it can only increase). You have to exert energy to solve the Rubik's cube. Even though your cube is now pretty, the amount of entropy in the system has increased (your new disorder is no. As you point out, the amount of useful energy in either is the same, but you have lost energy thus increasing the entropy of the total system.

    My advise is to reference http://hyperphysics.phy-astr.gsu.edu/hbase/Therm/entrop2.html and make sure you completely understand the paragraph on "Entropy in Terms of Heat and Temperature. (specifically, why it's defined in terms of dS instead of S)
     
    Last edited: Jun 11, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: How does evolution theory fit the entropy theory
Loading...