Insights You Will Not Tunnel Through a Wall - Comments

1. Aug 10, 2015

ZapperZ

Staff Emeritus
2. Aug 10, 2015

gianeshwar

Thanks ZapperZ.I have a better understanding now!

3. Aug 10, 2015

Markus Hanke

Good insight article, very well spoken !

4. Aug 10, 2015

Drakkith

Staff Emeritus
So I'm not going to tunnel through my chair and into the core of the Earth. Good to know!

5. Aug 11, 2015

maline

Does the differencebetween the proton & electron actually make the tunneling probability lower, or just much more difficult to calculate? if so, why?

6. Aug 11, 2015

vanhees71

Very nice Insight!

7. Aug 11, 2015

ZapperZ

Staff Emeritus
Look at the difference in the CHARGE! One sees it is a "barrier", while the other sees it as a "well". This means that the transmission probability for each one of them will be different!

This is not an issue of tunneling of individual particles. It is the tunneling of ALL the particles together, simultaneously, and coherently. We have not seen such a thing yet. The best that we have is the tunneling of alpha particles, which is nothing more than a clump of two protons (and notice that each of them making up the composite particle has the same charge and the same charge sign) while the neutrons have no charge.

Until we can show of tunneling phenomenon by whole atoms and molecules, tunneling by macroscopic object is practically impossible at this moment.

Zz.

8. Aug 11, 2015

maline

Would you mind putting in a word about what effect this has on the final probability?

9. Aug 11, 2015

ZapperZ

Staff Emeritus
I'm not exactly sure what you are looking for here. One particle has to tunnel through a barrier, while the other one has to "jump" over a "hole in the ground". Is it not obvious that the transmission probability will be different for each one of them?

So if you want just "a word", it is "DIFFERENT"!

Zz (who thinks explaining physics using "a word" is impossible).

10. Aug 11, 2015

maline

What I'm not getting is why the difference in the separate transmission probabilities necessarily leads to a lower probability that for the transmission of two particles with similar individual probabilities.

11. Aug 11, 2015

ZapperZ

Staff Emeritus
Because they won't get through the barrier with equal probability! Your right hand might go through, but your left hand stayed behind! (Sorry, but I had to resort to THAT ridiculous analogy.) So ALL of you didn't get through the barrier at the same time! To me, the probably of all of you to tunnel through the barrier is then ZERO.

Goodbye left hand!

Zz.

12. Aug 11, 2015

maline

If they did get through with equal probability, as in the case of alpha particles, how does this increase the probability for them both to get through at once?

13. Aug 11, 2015

ZapperZ

Staff Emeritus
Did you not pay attention to my description of the SIGN of the charges?

Zz.

14. Aug 11, 2015

maline

I have no problem with the fact that the two individual transmission probabilities are different. But what does this have to do with the joint probability of both particles being transmitted?

p.s. with all due respect, I don't think I'm the one who's "not paying attention" here!

15. Aug 11, 2015

ZapperZ

Staff Emeritus
Then I don't understand why you were using the alpha particle example, especially when clearly it doesn't apply to the "they" in your Post #12, if you are paying attention.

Whether you buy my argument or not, here's a fact: we have no experimental evidence of the tunneling of whole atoms and molecules.

If such an event can't be achieved, then there's no hope of tunneling whole watermelons.

Zz.

16. Aug 11, 2015

kmm

Maline. I would think of it like this. The probability of flipping a coin heads is 1/2. The probability of flipping two heads consecutively is 1/2*1/2=1/4. This is analogous to a the probability of a composite particle tunneling. So if you have an electron that has some probability X of tunneling through some potential barrier, and you have a proton with some probability Y of going through the barrier. Then the composite particle consisting of one electron and one proton will have a probability X*Y of tunneling and since Y<1, X*Y<X. That's what I expect anyway..

17. Aug 11, 2015

kmm

I should note, I don't think X*Y is the exact probability of electron and proton tunneling at the same time, but I expect the actually probability to have a similar form.

18. Aug 11, 2015

maline

Sure, two particles tunneling is less probable than one! But Zapper's statement was that a hydrogen atom is less likely to tunnel than an alpha particle, because of the fact that the proton & electron have different individual transmission probabilities. In your terms, we're comparing X*Y vs Z*Z. With classical probability, it would be completely irrelevant whether X=Y or not. So why is this aspect important here?

19. Aug 11, 2015

DaveC426913

Because the condition for success is that you (all of you) pass through the wall. Otherwise, none of you does. You encounter an impassible barrier.

Think of a mesh bag full of dice. Shake the bag, and each die has an individual chance of falling out of the bag.

But imagine if all the dice were stuck together with strands of gooey gum. Now, no die can literally fall out of the bag onto the floor, and the entire glop of dice will never fall out of the bag no matter how long and how hard you shake it. The chance of the entire glop of dice falling through are virtually zero, because it is a the sum of all the individual chances, which is a very small number.

Last edited: Aug 11, 2015
20. Aug 11, 2015

maline

Yes, I got all that from the start! But for the seventh time, how does the fact that the individual probabilities are different come into this?