Why is quantum mechanics not valid for large objects?

In summary, the conversation discusses the validity of quantum mechanics for large objects and the importance of understanding conventional physics before criticizing it. The speaker also questions the reliability of the video and suggests the need for multiple theories to explain different phenomena. The conversation also touches on the relationship between Einstein's theory of relativity and quantum mechanics. Overall, the conversation highlights the complexity and ongoing debate surrounding these topics in the scientific community.
  • #1
John Mcrain
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It this correct explanation why quantum is not valid for large object?
Why would small object want to hide their information?

 
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  • #2
It is valid for large objects.
 
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  • #3
Dale said:
It is valid for large objects.
How?
 
  • #4
John Mcrain said:
How?
It accurately predicts the results of experimental measurements. That is what it means for a theory to be valid.
 
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  • #5
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.
 
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  • #6
John Mcrain said:
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.
 
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  • #7
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.
 
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  • #8
A. Neumaier said:
No, since the conclusion is wrong.

For example, large superconductors can be explained only by quantum mechanics, not by classical mechanics.
AndreasC said:
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..
 
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  • #9
John Mcrain said:
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.

John Mcrain said:
Is Einstein relativity works/exist in quntum mechanics ?
Yes, modern QM, also called quantum field theory, is built on special relativity.
 
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  • #10
John Mcrain said:
Maybe we must have more theories for more cases..
Maybe we shoudl learn more conventional phsyics before complaining that its wrong.
 
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  • #11
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".
 
  • #12
Dale said:
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.



Vanadium 50 said:
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..
 
  • #14
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  • #15
Thread is closed for Moderation...
 
  • #16
John Mcrain said:
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.
 
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1. Why is quantum mechanics not valid for large objects?

Quantum mechanics is a theory that explains the behavior of particles at the subatomic level. It is based on the principles of uncertainty and superposition, which do not apply to larger objects. As objects increase in size, their behavior becomes more predictable and classical mechanics becomes a more accurate description.

2. What is the limit for an object to be considered "large" in quantum mechanics?

There is no specific size limit for an object to be considered "large" in quantum mechanics. However, as a general rule, objects with a mass greater than 10^-9 kilograms or a size larger than 10^-18 meters are considered to be in the classical realm and are not subject to the principles of quantum mechanics.

3. Can quantum mechanics be applied to macroscopic objects?

While quantum mechanics is primarily used to describe the behavior of particles at the subatomic level, it can also be applied to macroscopic objects under certain conditions. These conditions include extreme temperatures, pressures, or magnetic fields, where the classical behavior of the object breaks down and quantum effects become more apparent.

4. How does quantum mechanics differ from classical mechanics?

Quantum mechanics and classical mechanics are two different theories used to explain the behavior of matter. Classical mechanics is based on the laws of motion and gravity, while quantum mechanics is based on the principles of uncertainty and superposition. Additionally, classical mechanics is deterministic, meaning that the future behavior of a system can be predicted with certainty, while quantum mechanics is probabilistic, allowing for multiple possible outcomes.

5. What are the implications of quantum mechanics not being valid for large objects?

The fact that quantum mechanics is not valid for large objects has important implications for our understanding of the universe. It means that there are different rules at play at the subatomic level compared to the macroscopic level. This also raises questions about the fundamental nature of reality and the limitations of our current scientific theories.

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