# Quantum Tunneling- Walking through walls

1. Jan 3, 2010

### caljuice

I was on another forum and somebody was talking about quantum tunneling and that walking through walls was not impossible. Just highly improbable; the probability of it happening is older than the universe. Some reason it blew my mind away, even though not much was said. Anyone have more insight or thoughts on this subject? Does this mean it could be possible some building has phased through into the ground over these years? Or if my keyboard suddenly falls through my desk, I shouldn't be afraid of some supernatural cause but go hey, quantum tunneling.

2. Jan 4, 2010

### diazona

If your keyboard falls through your desk, you should be worried. Or perhaps you need to get a new desk.

Whenever someone asks this question, it puts us (physicists etc.) in a quandary of sorts: on one hand, according to quantum mechanics, the probability of any individual particle in your body suddenly being on the other side of a wall is not exactly zero, and so, mathematically speaking, yes, the probability that you would be able to quantum-tunnel through a wall might not be exactly zero. On the other hand, it's really really small. Unfathomably small. I not even sure we have a writing system capable of expressing how small this probability would be. (OK, actually, I'm sure the mathematicians have come up with something) Numbers like this are effectively zero. So in practice, it's never going to happen.

For what it's worth, I'm pretty sure the probability that you will spontaneously combust is way higher than that of your keyboard falling through your desk.

(P.S. probability can't be "older than the universe"... it's a number, not a time or an object)

3. Jan 4, 2010

### ZapperZ

Staff Emeritus
Please read this thread:

https://www.physicsforums.com/showthread.php?t=114110

Zz.

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