Does QM break down at large scales?

[cragar]

Main Question or Discussion Point

My friend and I were talking , and my friend said that the laws of QM break down at large scales , But i was thinking that they don’t break down the probabilities just become smaller and it becomes harder to use QM . So what do you guys think

 

[Matterwave]

They don't "break down"; instead, they approach the classical limit (make the same predictions as classical mechanics). See Bohr's principle of correspondence.
http://en.wikipedia.org/wiki/Correspondence_principle

 

[Redsummers]

As far as I know I would concur with your opinion. We all have heard sometime in our life that there's the possibility to pass through a wall, even though the probability is so small that the universe would reach the heat death before.

I guess these kind of calculations are made according to the amount of particles in the body that has to pass through such a wall. So I would say that the bigger, the less unlikely to happen.

 

[cragar]

i see , thanks for your answers