From what I read it was by the Heisenberg uncertainty principle but I don’t understand how, too technical for me when I read up on the topic
In: 0
Laplace’s Demon is basically a thought experiment which says if some hugely powerful entity could measure the exact position and speed of every particle in the universe, they could run that through a computer model and exactly predict what will happen in future. Now, it ought to be obvious nowadays there is a massive flaw in this even without Heisenberg–namely, to create the storage to store all this information would require more material than exists in the universe! Heisenberg just adds the cherry on the impossibility cake by telling us that you can’t possibly know both how fast a particle is moving and where it is at the same time, and obviously perfect information about both these factors is critical for Laplace’s demon to work.
LaPlace’s demon is a thought experiment if some creature/intelligence that has knowledge of the speed and position of every particle in the universe. Thus, this creature could predict anything that happens. It’s not about data storage or something like that, in this thought experiment the calculation power to predict the future based on the knowledge I described above is there.
Basically you answered your owm question in your post. The problem is you physically simply cannot know the position and the speed (i.e. energy level) of any one particle at the same time. That’s what Heisenberg’s uncertainty is all about. Since it’s impossible to determine both the position and the speed of particles at the same time, the whole thought experiment crumbles. Sure you could say that in the experiment it’s possible to do so but that would be breaking the laws of physics.
Its just incompatible with the largely accepted interpretation of quantum mechanics. Because in the so called “Copenhagen interpretation”, it is by postulate (assumed) true that we can know everything knowable about a system, but that some properties are not knowable so a hypothetical being that knows all positions and momenta is impossible.
There’s been more recent attempts that mathematically show using computation, that any Laplace demons are inherently uncomputable by other Laplace demons, so you can’t have any to start with.
To quote Wikipedia, Laplace’s “demon” idea suggests:
> if someone (the demon) knows the precise location and momentum of every atom in the universe, their past and future values for any given time are entailed; they can be calculated from the laws of classical mechanics.
i.e. if we know everything about *now* we can figure out everything in the past and everything in the future.
The uncertainty principle (again, quoting Wikipedia) means:
> the more precisely the position of some particle is determined, the less precisely its momentum can be predicted from initial conditions, and vice versa.
If the uncertainty principle is true, then Laplace’s “demon” cannot exist, as it cannot know both the position and momentum of *any* atom in the universe; the more it knows about the position, the less certainty it has over the momentum and vice versa.
In fact the Copenhagen interpretation of quantum mechanics takes us even further, and we get that there is always uncertainty in any (quantum) measurement; we cannot precisely predict the position *or* momentum of any (quantum) particle in the future even given perfect knowledge now, all we can do is come up with an estimate for where it could be, and what the probability of finding it there is.
The Copenhagen interpretation of quantum mechanics is *non-deterministic*; that is to say the future isn’t uniquely or necessarily determined by the present – there is true randomness.
Of course, there are other interpretations of quantum mechanics, which *are* deterministic (either via something like the Many Worlds Interpretation – although that is only deterministic on the multi-verse scale, or interpretations which don’t have localism).
There are also logical attempts to disprove Laplace’s demon, but they tend to be more technical counter-arguments (the “demon” couldn’t know all its future memory, or if you had two demons they wouldn’t be able to know everything about the other) and less important in thinking about determinism.
From what i understand, it is because the required information about each particle, atom, etc. creates more entropy than what is reduced by arranging the particles in a lower entropy state. Basically, information results in raised entropy.
Latest Answers