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Does random exist?

  1. Jul 21, 2008 #1
    Not sure where to put this, or if this even belongs on these forums at all.

    But recently I was thinking about random, probability clouds, and the like.

    Does random actually exist or is it simply another way of saying “too complicated for us to know right now”

    Obviously in questioning a word you need to agree on a definition first, I used the first line from google”define:random”

    “lacking any definite plan or order or purpose; governed by or depending on chance; "a random choice"; "bombs fell at random"; "random movements"

    It just seems to me that everything we call random, is just something with a ton of variables, or something with variables so small we cannot measure them without changing them.

    Feynman constantly corrects himself in his lectures after saying random, with “very complicated”

    Please move this to the correct section if needed or simply delete if it has no business being here 
  2. jcsd
  3. Jul 21, 2008 #2


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    The time for an individual radioatactive atom to decay is random - or there is a mechanism we don't understand yet.!
    That the famous Einstein quote that "God doesn't play dice" - he beleived that there must be some mechanistic process we didn't know about.
  4. Jul 21, 2008 #3
    I know of plenty of "random" things we have declared in science, because at this time we dont fully understand it. So to progress any further in something that involves this "random"
    feature, we need to refer to it as random.

    But I guess my question was more "(should/do) science related people/fields believe (truly) in random, as it is in a sense giving up (even if temporarily)"

    If you know something isnt actually random, but is random enough to not be known as of now, you still know there is a reason for it, and may someday return to it to fully understand.

    But if you consider something truly random, there is no reason to ever fully understand it, as understanding it as random, is fully understanding it.
  5. Jul 21, 2008 #4
    Chaos is. I think on the quantum level fields act and react chaotically.

    Removing "random" from existence is implicit of design. The size, velocity, direction the earth blew out of the big bang, with all of the elements it has... life the universe and everything being "designed"... asteroids who's sole mission is to be chewed up entering our atmosphere...

    I would say chaos exists. It is really more philosophy than physics, as it is not at all provable... which is the only reason I bother posting. Physics is not my friend.
  6. Jul 21, 2008 #5
    I guess this is more of a philosophy question. :-\

    But I also think its relevant to sciences in that, if a scientist were to deem something random, they may be prone to never investigating the situation more.

    It basically boils down to an almost religious question. Is it possible for an uncaused cause to exist. We generally expect things to follow the cause/effect logic, but for the concept of true random/chaos to exist, it would have to break that logic.

    Sure a chaotic event could be cause, but that’s a much higher level. When the actual chaos is looked at, there would have to be effects without cause at some point.

    Or am I spouting broken logic now?

    I looked into chaos a bit more and found

    So it seems that even chaos is tightly rule-bound but very sensitive to its initial state.
    So its a game of working out all the variables, which is what science is all about right?
    Last edited: Jul 21, 2008
  7. Jul 21, 2008 #6
    Just a quick note; if interested in the mathematics of chaos and randomness, read the book "Chaos" by James Gleick
  8. Jul 22, 2008 #7
    Whoa! Chaos, in a technical sense, is very far from involving randomness!

    Chaos is always deterministic: if you know the current state exactly, you can predict the future state at anytime.
  9. Jul 22, 2008 #8
    awesome! Im glad I interprited that correctly. Thats what I was trying to get at the entire time.

    Anything random, or chaotic just seems to me as though it is very much dependant on the variables at the exact state ..

    Now, Im not sure if this is allowed on these forums or not, but I've always thought this also applied to people, decisions.

    Most science people I talk to about this, agree that nothing is actually random, random is just a useful word we use to describe something too complicated for us to know atm.

    But most disagree when it comes to people. "I can randomly punch you in the face right now"

    Isnt this still deterministic based on their current brain chemistry/dna/etc etc?

    (sorry this is getting bio, but I find that bio is just a higher abstraction of physics isnt it?)
  10. Jul 22, 2008 #9

    Claude Bile

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    You touch on the issue of determinism; prior to the 20th century (i.e. the era of "classical" physics), the standard attitude amongst physicists was that, provided we have sufficient information about a system (even one as large and complicated as our universe) then we can in principle predict the behaviour of the system for all time.

    The discovery of quantum phenomena challenged this long-standing philosophy. Some argued that quantum phenomena are truly random whilst others insisted that there is some underlying mechanism that produces results that are only seemingly random.

    It is now readily accepted amongst physicists that quantum phenomena are truly random. "Classical" randomness (like rolling dice), we now understand to be deterministic, and are only perceived as random through lack of information.

    The connection between quantum randomness and how it might seed our perception of "freedom of choice" so to speak on a biological level is very poorly understood.

  11. Jul 22, 2008 #10


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    Although the equations of motion in "deterministic chaos" are, well, deterministic, the point is that they act on real number quantities. And you can never know a real number "precisely". It takes an infinite amount of information. So the randomness in deterministic chaos comes about from the fundamental impossibility to know an initial state made up of real numbers precisely.
    In other words, the randomness doesn't come from the dynamics, but from the initial conditions, but is unavoidable.
  12. Jul 23, 2008 #11
    Lets say you had a collection of information. If you continue to break the information down, it seemingly becomes more and more random. Deterministic processes occur smoothly, meaning that you could break the processes down and assess all the mechanistic features allowing for the phenomenon to occur. Now if the process seems to occur by itself (meaning there are no mechanistic elements to it), it tends to become more random...technically, when we call something random, it is because we do not know how it works in a deterministic manner (if it does).
  13. Jul 23, 2008 #12
    I find this just about as disturbing as a religious person would find my argument.

    Ive been searching around and find a decent amount of opposition to "quantum phenomena is truely random"

    Feynman, while explaining his diagrams and paths of photons made sure to explain that using probability clouds/paths are our best means of making anything of what we are viewing, but that this does not mean these events/phenomena are actually random, but just out of the reach of our current instrumentation.

    I makes sense to me that it would be hard to measure the position of a baseball, by throwing baseballs at it. If we are trying to test the smallest known particles (some i dont think we are even positive exist, like gravitrons? again... not sure, im new here :D) I can swallow having a hard time, and confusing results when experimenting using machines made of the things we are measuring.
  14. Jul 23, 2008 #13


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    So is the Schroedingers cat dead, or alive?

    I thought Laplace's daemon was impaled with aspen stake by Heisenberg's uncertainty principle.
  15. Jul 23, 2008 #14

    Andy Resnick

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    A dynamic variable- position, direction, phase, etc. can indeed be random, and random has a well-defined mathematical sense as well.

    Consider the two-point correlation function of a continuous variable- a measure of how well we can predict field values are *there and then* given knowledge of it *here and now*. Note that this knowledge can be exact.

    An incoherent field has zero predictability, while a coherent field has infinite predictability. Real physical fields are partially coherent, meaning that our ability to predict future values is limited but non-zero.
  16. Jul 23, 2008 #15
    i think it was an excellent point that in science we determine things with a cause/effect relationship... and if we cannot determine a cause it may seem to be random but once we figure out the cause it is no longer random...

    heres an example...

    rain drops landing on the ground in certain locations may seem random when looking at the ground.. but when we find out where and when the rain drop starts to fall we can dynamically predict where it will land... and then you can say that raindrops land in locations, random, in relation to each other but if we figure out why the raindrops fall and what are all the exact causes, we may be able to determine where every raindrop lands and why!
  17. Jul 23, 2008 #16
    The Schrödinger’s cat experiment relies on true randomness of radioactive decay right?

    What I am questioning, is the randomness of this decay. Things seem to follow (based on past history and science) that things are random until proven. We use probability to estimate something unknown, or not-easily measurable at the given time, with out given instrumentation.

    Is it impossible to measure a photon's position without altering its future path? (I'm pretty sure right now it is) but would you go so far as to say its impossible period?

    Im not going out on the Disney limb and claiming "anything’s possible"

    But to me, science has always been awesome because it constantly proves itself wrong. To some this is disconcerting. To me, it simply shows that we are making progress. If we picked one thing, and stuck with it, without questioning it I think science would be considered a religion.

    An incoherent field by definition has zero predictability, this doesn’t mean it is in anyway real right? By talking about the concept of "truly random" just because we have a word for a concept, does not mean it exists, or could exist.

    I personally believe our ability to predict the future value of any given experiment is based on how much information we have about the starting state, and information about the rules of interactions that would occur during the experiment.

    Ie, tossing dice (material, height, velocity, angle, pitch ,yaw ,roll ,weight , floor material, etc etc, and the rules for interactions would be basic physics collisions)

    This is exactly what I was thinking, I just wanted to see how many other people on here felt the same.

    It seems like random is a cop-out for not accepting the fact that we dont know. Some people cannot stand not knowing things, and it would seem as though random came about from these types of people. There are also some people who are perfectly fine with not knowing.

    Feynman-"I can live with doubt and uncertainty and not knowing. I think it is much more interesting to live not knowing than to have answers that might be wrong."
  18. Jul 23, 2008 #17
    wow, I've never seen this argument before. :) Thats really cool!

    But I guess Im not fully understanding heisenbergs unceretainty principle then.

    "In quantum physics, the Heisenberg uncertainty principle is the statement that locating a particle in a small region of space makes the velocity of the particle uncertain; and conversely, that measuring the velocity of a particle precisely makes the position uncertain."

    but the laplace daemon implys position and velocity.

    as vanesch said, its impossible for us to know everything precicesly, which is why random seems so real.

    But this doesnt mean that random exists in any sense other than what vanesch said "In other words, the randomness doesn't come from the dynamics, but from the initial conditions, but is unavoidable."
  19. Jul 23, 2008 #18


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    Laplace had no idea about uncertainty principle, so he thought world is completely determinitic.

    Uncertainty principle tells that we can't know exact speed and exact position at the same time. It is not an effect of the low precision of our instruments. It is the intrinsic property of our world. The better we know the speed, the less we know about the position and vice versa.

    In other words, Heisenberg train moves with exactly 30 mph, we just don't know if it is on rails :wink:

    Sure uncertainty of train position is so small that it completely doesn't matter.
  20. Jul 23, 2008 #19
    right, but in the theoretical situation that we did know both, everything would be deterministic from that point on right?
  21. Jul 23, 2008 #20


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    This is a pure speculation, so we can get to any conclusions you want :smile:
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