ELI5- Will we ever be able to predict the future?
In short- no. Quantum Mechanics and one specific aspect called the Uncertainty Principle show that it is impossible.
What is the Uncertainty Principle?
The Uncertainty Principle was formulated by a German scientist, Werner Heisenberg. To quote the late Stephen Hawking from his book A Brief History of Time, "in order to predict the future position and velocity of a particle, one has to be able to measure its present position and velocity accurately." ie, we have to know exactly where something is and how fast it is moving, and in which direction, to know what it will do next.
So why can't we do this?
Well the important thing to remember here is that we are talking about tiny particles- so small, in fact, that a light wave is enough to change their velocity, or future path. And what is it that we need to determine the position of the particle? Well light of course. The measurement can then be only as accurate as the distance between the crests of the light wave, however as we increase the frequency of the lightwave, the more energy it has and the more it will disturb the particle, changing its path.
This simple diagram from Lumen Learning hopefully illustrates what I'm saying.
So to sum it all up- the more accurately you try to measure the position of a particle, the less accurately you will be able to measure the velocity. If we can't even measure the present state of the universe, we certainly can't predict its future state!
So there's a limit to how accurately we can measure something- is this an actual number?
Yes. It uses Planck's Constant which is a fundamental of quantum mechanics and it's an inequality which looks like this:
ΔxΔp > h-bar/2
where h-bar = 1.054571800(13)×10−34 (Joules per second)
x= position and p= velocity
It is basically saying that the standard deviation of position multiplied by the standard deviation of velocity will always be more than this number. Yes- it's a tiny number, but in the subatomic world things are tiny.
But could we ever have the technology to measure the particle's position even more accurately?
Now this is the funny thing. This is actually only an analogy, and it is a fundamental law of the universe that the position and velocity of a particle can't be measured completely accurately.
This from Wikipedia pretty much sums it up:
"Heisenberg utilized such an observer effect at the quantum level as a physical "explanation" of quantum uncertainty. It has since become clearer, however, that the uncertainty principle is inherent in the properties of all wave-like systems, and that it arises in quantum mechanics simply due to the matter wave nature of all quantum objects. Thus, the uncertainty principle actually states a fundamental property of quantum systems and is not a statement about the observational success of current technology. It must be emphasised that measurement does not mean only a process in which a physicist-observer takes part, but rather any interaction between classical and quantum objects regardless of any observer."
So we'll never be able to predict the future?
No, not completely anyway. However, in normal life, we can predict things such as the path of a car fairly accurately as the uncertainty principle is only a visible effect in the subatomic world for most situations.
It's worth noting that prior to the introduction of the uncertainty principle, many scientists believed that the universe was completely deterministic, and that there was a set of fundamental laws that when discovered would allow us to predict everything that would happen in the universe, the theory being led by a French scientist, Marquis de Laplace.
Please comment any suggestions and/or questions.
What is the Uncertainty Principle?
The Uncertainty Principle was formulated by a German scientist, Werner Heisenberg. To quote the late Stephen Hawking from his book A Brief History of Time, "in order to predict the future position and velocity of a particle, one has to be able to measure its present position and velocity accurately." ie, we have to know exactly where something is and how fast it is moving, and in which direction, to know what it will do next.
So why can't we do this?
Well the important thing to remember here is that we are talking about tiny particles- so small, in fact, that a light wave is enough to change their velocity, or future path. And what is it that we need to determine the position of the particle? Well light of course. The measurement can then be only as accurate as the distance between the crests of the light wave, however as we increase the frequency of the lightwave, the more energy it has and the more it will disturb the particle, changing its path.
This simple diagram from Lumen Learning hopefully illustrates what I'm saying.
So there's a limit to how accurately we can measure something- is this an actual number?
Yes. It uses Planck's Constant which is a fundamental of quantum mechanics and it's an inequality which looks like this:
ΔxΔp > h-bar/2
where h-bar = 1.054571800(13)×10−34 (Joules per second)
x= position and p= velocity
It is basically saying that the standard deviation of position multiplied by the standard deviation of velocity will always be more than this number. Yes- it's a tiny number, but in the subatomic world things are tiny.
But could we ever have the technology to measure the particle's position even more accurately?
Now this is the funny thing. This is actually only an analogy, and it is a fundamental law of the universe that the position and velocity of a particle can't be measured completely accurately.
This from Wikipedia pretty much sums it up:
"Heisenberg utilized such an observer effect at the quantum level as a physical "explanation" of quantum uncertainty. It has since become clearer, however, that the uncertainty principle is inherent in the properties of all wave-like systems, and that it arises in quantum mechanics simply due to the matter wave nature of all quantum objects. Thus, the uncertainty principle actually states a fundamental property of quantum systems and is not a statement about the observational success of current technology. It must be emphasised that measurement does not mean only a process in which a physicist-observer takes part, but rather any interaction between classical and quantum objects regardless of any observer."
So we'll never be able to predict the future?
No, not completely anyway. However, in normal life, we can predict things such as the path of a car fairly accurately as the uncertainty principle is only a visible effect in the subatomic world for most situations.
It's worth noting that prior to the introduction of the uncertainty principle, many scientists believed that the universe was completely deterministic, and that there was a set of fundamental laws that when discovered would allow us to predict everything that would happen in the universe, the theory being led by a French scientist, Marquis de Laplace.
Please comment any suggestions and/or questions.
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