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But if everything is random how can we have definite laws like newtons laws, electromagnetic laws. I mean if everything is random at the lower level these laws will also vary right, they can't be fixed!

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- Thread starter Avichal
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But if everything is random how can we have definite laws like newtons laws, electromagnetic laws. I mean if everything is random at the lower level these laws will also vary right, they can't be fixed!

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But if everything is random how can we have definite laws like newtons laws, electromagnetic laws. I mean if everything is random at the lower level these laws will also vary right, they can't be fixed!

Things APPEAR random if you make one measurement of one thing at a time. However, this is extremely unusual. Our normal world deals with us making "measurements" (or interactions) a gazillion times each picosecond! When that occurs, then quantum mechanics make very accurate and uncanny predictions, and classical mechanics appear to not be random, resulting in our theories being quite accurate.

Zz.

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In theory, you could run into a wall and the spaces between your molecules and the wall's molecules could line up exactly right so that you would pass right through it (it's called quantum tunnelling). But the chance is so low, you could run against the wall 100 times a second til the Earth is engulfed by the sun transitioning to a red giant and it still probably wouldn't happen.

On the other hand, we exploit quantum tunnelling on a small scale all the time in modern computing. We manipulate the chances so it is more likely an electron will go through the "wall".

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Think of flipping a coin. It will come up either 'heads' or 'tails', randomly. It will NOT come up 'red', or 'negative', or 'charmed' - ever. Those are not options available for a coin toss.

The laws come up in defining the options, not the outcome.

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Think of flipping a coin. It will come up either 'heads' or 'tails', randomly. It will NOT come up 'red', or 'negative', or 'charmed' - ever. Those are not options available for a coin toss.

The laws come up in defining the options, not the outcome.

The outcomes, and the relative probabilities for those different outcomes. Hence the predictive power of quantum mechanics.

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I would take the example of newton's laws since they are very easy: -

First law states that a body would continue to move in the same velocity as long as not acted upon any force. But the individual atoms or molecules could change their energy and suddenly speed up or slow down right? But that has a very low probability and as an approximation we have the first law.

Is my interpretation right?

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For example, a particle in its eigenstate will remain in its eigenstate and will may be easily predicted. Also, even though it's not possible to predict when exactly an excited state will decay, it's perfectly possible to predict the average time it will the decay, given many particles. So the varible called "average decay time" is not random at all.

Furthermore, as has been pointed out by others above, what is random in any case is only the particular outcome of an event/interaction. The laws governing that event is not random, it's just that the laws act on "probabilities". How those probabilties evolve under the laws can be very well defined, it's just that they are still probabilties in the end, which is why the outcome may not be predictable.

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Everyone says that newtons laws are not entirely correct. They are just an approximation...I want to know if this is true

Is the above interpretation right?First newton law states that a body would continue to move in the same velocity as long as not acted upon any force. But the individual atoms or molecules could change their energy and suddenly speed up or slow down right? But that has a very low probability and as an approximation we have the first law.

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I want you to give my an example of a law.

Everyone says that newtons laws are not entirely correct. They are just an approximation...I want to know if this is true

Is the above interpretation right?

This makes very little sense because we have not detected what you quoted. So you are essentially asking us to explain something that has never happened.

Note that even for elementary particles, we haven't seen such a change in trajectory that you are describing. So what you claim is unverified and highly speculative.

Zz.

- #10

sophiecentaur

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Take most laws and you will find apparent exceptions to them. That doesn't make them any less valid or useful even if it may be personally upsetting.

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-Dave K

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I would take the example of newton's laws since they are very easy: -

First law states that a body would continue to move in the same velocity as long as not acted upon any force. But the individual atoms or molecules could change their energy and suddenly speed up or slow down right? But that has a very low probability and as an approximation we have the first law.

Is my interpretation right?

No. Random doesn't mean particles can defy the laws of physics. It just means that, on some level, we can't predict the exact values of a tied pair of variables ( such as momentum and position) within a certainty of plank's constant. So any given particle has a wavelength. And we can't predict exactly what it's momentum (speed) or position will be at some given moment in the future. But that doesn't mean it can be anywhere or do anything. It is still confined by the wave function.

But wavelengths can cancel and amplify each other. So when you add particles together to scales above the quantum level, they behave in an extremely predictable fashion.

When people say Newton's Laws are an approximation, they are often refering more to Einstein's relativity, which expands Newton's laws to situations of extreme velocity and acceleration.

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No. Random doesn't mean particles can defy the laws of physics. It just means that, on some level, we can't predict the exact values of a tied pair of variables ( such as momentum and position) within a certainty of plank's constant. So any given particle has a wavelength. And we can't predict exactly what it's momentum (speed) or position will be at some given moment in the future. But that doesn't mean it can be anywhere or do anything. It is still confined by the wave function.

But wavelengths can cancel and amplify each other. So when you add particles together to scales above the quantum level, they behave in an extremely predictable fashion.

Oh okay that made me understand a bit. I had the wrong notion of random. I need to take a course on quantum mechanics as soon as possible!

When people say Newton's Laws are an approximation, they are often refering more to Einstein's relativity, which expands Newton's laws to situations of extreme velocity and acceleration.

Thanks for correcting me.

So can the macro-laws be derived by adding all the wave-functions of particles in an object

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Oh okay that made me understand a bit. I had the wrong notion of random. I need to take a course on quantum mechanics as soon as possible!

Thanks for correcting me.

So can the macro-laws be derived by adding all the wave-functions of particles in an object

Yes, to high accuracy. Although very soon the processing power required becomes the limiting factor.

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