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pivoxa15
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I can think of two principles which explains why I can't lesuirely walk through a concrete wall. The HUP and Pauli's exclusion principle. Which one contributes more?
It doesn't per se.Demystifier said:I do not see how HUP (Heisenberg uncertainty principle) forbids walking through the wall.
Can someone explain me that?
It doesn't, it's what PERMITS you to walk through a wall, for sufficently small values of wall.Demystifier said:I do not see how HUP (Heisenberg uncertainty principle) forbids walking through the wall.
dextercioby said:If i was to be launched through a cannon at 100 Km/hr there would be parts of me passing through a 10 cm brick wall found 10 m away from the cannon. Too bad i'd die without picking up the glory.
What does passing through a wall have to do with quantum physics ??
dextercioby said:What does passing through a wall have to do with quantum physics and the "default state of the universe" ??
DaveC426913 said:the OP's question was phrased as asking why he "can't lesuirely walk through a concrete wall". In fact, that question doesn't really need to be answered, as it is usually the case. The question he should be asking is [..]
Take a single alpha particle and send it flying into a 1cm thick slab of metal at a speed of about 0.9c. A rough estimate of the probability that it comes out the other side gives me a number smaller than 1 part in 10,000. Trying to get a single alpha particle through at a "leisurely walk" is itself less likely than a ppb, forget about a macroscopic network of atoms!pivoxa15 said:I can think of two principles which explains why I can't lesuirely walk through a concrete wall. The HUP and Pauli's exclusion principle. Which one contributes more?
Billygoat said:This means that Pauli exclusion, and HUP aren't important. The reason you can't walk through the wall is due to the electrostatic repulsion between your electrons and the wall's.
pivoxa15 said:I can think of two principles which explains why I can't lesuirely walk through a concrete wall. The HUP and Pauli's exclusion principle. Which one contributes more?
ueit said:It enables you to calculate the probability to pass through a wall but doesn't tell you "how" and "why", it lacks a detailed mechanism.
JDługosz said:I thought it follows from fundamentals of QM. The probability of the electron being where it doesn't belong becomes zero. The wave function reflects that fact. The presence of the other electron affects the sum of all possible paths, and stores the potential energy by affecting the function that is confining the electron to its energy well. That is, the orbitals become distorted and smaller.
However, on the TV show "Braniac" they have a segment on "Things you can run through".
ueit said:And how is this an explanation for tunneling? That's exactly what I was saying. You can calculate the probability to find an electron here or there, and that's it.
genneth said:Remember that physics is about numbers, not words.
JDługosz said:Sorry, I was thinking of how Pauli exclusion makes a wall "hard".
quetzalcoatl9 said:and let's not forget our good friend electrostatics..
JDługosz said:See post #13. Sorry I can't find a reference.
JDługosz said:Do you have a reference? I was taught that Exclusion dominates for ordinary solids like bricks. The electron repulsion is easily overcome by momentum, and only starts to show when the atoms' shells start to overlap anyway. The Pauli exclusion then builds faster than the electric repulsion.
section 2.7 on page 48 said:All the different kinds of interactions we have discussed so far have been attractive forces. There must also be some repulsive force, otherwise molecules would collapse. Two types of repulsive force have been considered in the preceeding sections: the Coulomb repulsion between like-charged ions, and the repulsion between atoms and molecules brought too close together which are very short-range. When repulsion occurs between to ions it is generally called Born repulsion. For the second example, the repulsive forces increase very suddenly as two atoms or molecules approach each other very closely, this is due to the repulsion between electron clouds overlapping at very small separations. This repulsion, which increases very steeply with decreasing distance, is due to the Pauli principle, which forbids outer electrons of one molecule from entering occupied orbitals of the other. This repulsion is called hard core or Born repulsion. We will use the name hard core repulsion for the interactions between two uncharged molecules in order to discriminate them from ionic repulsions. These repulsion interactions are quantum mechanical in nature and there is no general expression for their distance dependence, but some empirical potential functions are derived. Ha4rd core repulsions are responsible for the magnitude of the densities of solids and liquids.
Nice citation!JDługosz said:Surface Chemistry of Solid and Liquid Interfaces By H. Yıldırım Erbil states that [.."..]This repulsion, which increases very steeply with decreasing distance, is due to the Pauli principle, which forbids outer electrons of one molecule from entering occupied orbitals of the other.[.."..]
quetzalcoatl9 said:in computer simulations of most materials/fluids[..]
cesiumfrog said:Q', do you have anything more solid (oops) to support your side (since so far it looks like I have to renounce my attributions to Coulomb force)?
Are those the ones that someone won the noble Prize for? :grin:quetzalcoatl9 said:Nobel gases. which, I will point out, are not in the solid phase under STP.