Why is quantum mechanics not valid for large objects?

[John Mcrain]

It this correct explanation why quantum is not valid for large object?
Why would small object want to hide their information?

 

[Dale]

It is valid for large objects.

 

[John Mcrain]

It is valid for large objects.

How?

 

[Dale]

How?

It accurately predicts the results of experimental measurements. That is what it means for a theory to be valid.

 

[Vanadium 50]

John John, John, "Watch this video and explain it to me" is a big, big ask.

Making statements - especially false ones, hoping to be corrected - is a poor way to learn. Questions are better.

Now, Dale is 100% right. QM works perfectly well for macroscopic objects. There are a few problems like this in French&Taylor and Eisberg&Resnick. This tends not to be a very practical approach - why spend an hour doing a calculation when the classical version takes seconds? But you can do it.

 

[A. Neumaier]

It this correct explanation why quantum is not valid for large object?

No, since the conclusion is wrong.

For example, large superconductors can be explained only by quantum mechanics, not by classical mechanics.

 

[AndreasC]

It is completely valid. It's just that in large objects, there is often a kind of "averaging" effect taking place that results in the (much more complicated) QM solution giving more or less the same thing as good old classical mechanics. So you could in principle just use quantum mechanics to predict the course of a ball that is thrown into the sky, but that would be much more complicated for basically no reason and it would give you more or less the same result as just doing the simple classical calculation. It is similar to how you don't use special relativity for the same problem. It's valid, it's just pointless.

Of course, this is not the case for other problems, in many cases effects specific to quantum mechanics are important for the examination of large objects.

 

[John Mcrain]

No, since the conclusion is wrong.

For example, large superconductors can be explained only by quantum mechanics, not by classical mechanics.

It is completely valid. It's just that in large objects, there is often a kind of "averaging" effect taking place that results in the (much more complicated) QM solution giving more or less the same thing as good old classical mechanics. So you could in principle just use quantum mechanics to predict the course of a ball that is thrown into the sky, but that would be much more complicated for basically no reason and it would give you more or less the same result as just doing the simple classical calculation. It is similar to how you don't use special relativity for the same problem. It's valid, it's just pointless.

Of course, this is not the case for other problems, in many cases effects specific to quantum mechanics are important for the examination of large objects.

Men In the video has engineering and phsysics degree, so why he post wrong theory or this video is made for kids?

Is Einstein relativity works/exist in quntum mechanics ?

Obvuisly classic physics dont work for electrons/atoms, but that not mean it is wrong for big objects as well, so why people think that one theory must works for micro and macro world?

Maybe we must have more theories for more cases..

 

[Dale]

Men In the video has engineering and phsysics degree, so why he post wrong theory or this video is made for kids?

This is precisely why such videos are not considered professional scientific sources. They are not subject to the same review and publication standards as the professional scientific literature.

As far as why someone would post such material, you would have to ask them. However, regardless of their motivation it is simply not correct that QM is not valid for large objects.

Is Einstein relativity works/exist in quntum mechanics ?

Yes, modern QM, also called quantum field theory, is built on special relativity.

 

[Vanadium 50]

Maybe we must have more theories for more cases..

Maybe we shoudl learn more conventional phsyics before complaining that its wrong.

 

[Jarvis323]

The video isn't saying QM isn't valid for macroscopic objects, it is trying to explain why,

"In our everyday experience, we will not see quantum superposition or wave-like behavior of macro objects".

 

[John Mcrain]

This is precisely why such videos are not considered professional scientific sources.

Which explanation of these two is corrrect?
Sabine tell all this explanations are wrong.

Maybe we shoudl learn more conventional phsyics before complaining that its wrong.

Man from my video say that electron will crash into nucleus using classic physics, so he conclude it cant be used for micro world..

 

[Dale]

Which explanation of these two is corrrect?

This one: https://theoreticalminimum.com/courses/quantum-mechanics/2012/winter

 

[John Mcrain]

This one: https://theoreticalminimum.com/courses/quantum-mechanics/2012/winter

Until new theory comes out and prove this one wrong.
Maybe is better to wait 200,300 years, that the scientists find final one and agree among themselves that is correct.
Sabine Hossenfelder

 

[berkeman]

Thread is closed for Moderation...

 

[Dale]

Maybe is better to wait 200,300

Yes, maybe it is better to wait until then. In the meantime (after a very brief discussion among the mentors) this thread will remain closed.