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I've just finished reading Einstein's Biography by Walter Isaacson.

  1. Apr 9, 2008 #1
    I've just finished reading Einstein's Biography by Walter Isaacson. There is a pasage that got me thinking about the way Einstein observed the universe and his distaste for quantum mechanics. Einstein is famous for declaring that God dose not play dice, basically what he was saying is that, even though we perhaps do not fully understand what is happening there is a strict set of rules governing reality. From what i understand, quantum mechanics states that one cannot predict to an absoulte certainty what and where something(such as a particle) will happen next, it can only predict the possibilities of what or where something will happen next, in other words as one observes in greater detail the postion of a particle one loses the detail of its vector and vice-versa. I think thats right..anyway...
    I was sitting outside late one night after it had rained and drops of water were on occasion dropping off the roof, now of course one could not predict exacly when and where they would drop off but it made me think that there was some rule determining when and where it would, the water would build up until it hit breaking point and was too heavy too support its own weight and fall to the ground under graivty. To me that looks like a definite line upon when reached a significant event would happen. In other words there was no chance involved just a series of events that led upto the final action (the raindrop hitting the ground). of course there are many factors involved and the calculations to acheive a accurate prediction would be extremly and perhaps impossible at out level of understanding but what i think im trying to say is that to me there seems like a strict causality in our universe even if perhaps we still dont full understand it. What do you think?
     
  2. jcsd
  3. Apr 9, 2008 #2
    And Steven Hawking said "Not only does God play dice, he throws them where you can't see them."

    As I recall my father's lectures the question boiled down to what makes science science. In Einstenin's view all things proceeded from precepts proven to be true or false, no matter how small. Things could be proved to be, or proven not to be, and all in the middle ground was "yet to be detirmined". In later mathematics a physics, say quantum or string or other, the question was not about defining whether a thing is, or is not, but how likely at a given juncture or event a property was likely to manifest or not.

    The devil is in the details apparently. For the case of your raindrop, the mathemematics would still have the drop fall, but the question became one of timing. Within what period of time is it important that we know it will drop? Minutes? Seconds? Microseconds? Nanoseconds? And which molecule on the surface of the raindrop hits first and how much does it matter?

    As the in house physicist for GE in Peterborough designing the control mechanisms for the first production electrical generation nuclear reactor the differences mattered very much to him in the late 1950's when what we knew of atomic reactions were generally large and not envioronmentally friendly, to say the least if you get my drift. It bothered him enormously. But in the end, it is a question of "how much do you need to know?"

    We know if you drop a hammer it will fall. Do you need to be able to calculate which exact molecule of the hammer makes first impact with the ground? What difference will it make? (In the sense of if it matters that much, perhaps you need to make a more robust control system....)

    We do not need to understand the universe before we start, just understand enough that when we strive to take our first steps we do not step off a cliff.
     
  4. Apr 10, 2008 #3
    I guess it all boils down to the question of is it theoretically possible to calculate the exact postion of every particle and its vector then calculate what happens next. I can understand when one is calcualting for something like the control mechanisms you spoke of one need to consider how far one needs to go to acheive their goal yet i wonder if it were possible to go all the way, no holes barred one would truly be able to predict the outcome to the utmost degree and thus predict the fate of the universe down to the tinest blade of grass or that this in it self is impossible because of a little thing called freewill among many other factors.
     
  5. Apr 10, 2008 #4
    Scoobydoo there is a distinction between predictability and causality. If there is no causality one can obviously not predict, but even if there is causality it is not guaranteed that one an predict.
     
  6. Apr 10, 2008 #5
    Is that true though? couldnt it be that if there is causality then one can always predict?
     
  7. Apr 10, 2008 #6
    As far as I can tell, one of the big things of Quantum Mechanics is that there in fact is no distinct cause for the location of a particle. That's why you have a probability. The particle doesn't know where it is until you measure it, as my professor told me.

    It's different than flipping a coin, because in that case you could calculate the mass of the coin, torque, force, gravity, etc., and after a tedious calculation get an answer. With QM there isn't (or at least we haven't found) any mechanism that would directly decide the outcome like that.

    We do, however, have a solid framework behind it, so all of our "probably" and "maybe" are backed up by experiment. So we know the HOW, but not the why (err... I guess). The problem is, how do you even tackle a question like that? Is it something for philosophers to answer?
     
  8. Apr 10, 2008 #7
    Good question! Maybe this one should be left to the philosophers yet i somehow i feel that physics holds the answers to this question. I'm not that knowledgeable on string theory but maybe that holds the answer. I like the idea that the universe is a huge symphony at the uncutable but like an unheard song its would be difficult to know what comes next, although the universe could be singing to some degree a repetative tune,infact i would assume it would have to be in order to maintian its exsistence, each repetition would have to be slightly differnt from the last in order to move forward, without change time would stand still and there would be no universe. Still is this change always predictable or only sometimes? ;) gotta love it
     
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