Hello:
I was reading my book on time and the author went into a section on quantum mechanics. He then went into the tunnel effect and particles barrowing energy to make it through a barrier, but this section is somewhat short and left me with some questions.
1. From where does the particle barrow energy?
2 How does the particle know how much energy to barrow?
3. How does the particle even know the barrier is there before running
into it?
If someone could shed some light on these questions that would be great. Thank You

The particle doesn't borrow energy, really. A wave function of a particle "striking" a barrier will extend through the barrier, and (depending on the height and width of the barrier) have a nonzero value on the other side. So there's a probability of appearing outside.

The idea of borrowing energy to get over the barrier is classical. Tunneling is a quantum effect.

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Should I assume the author to be incorrect describing the effect in classical terms, or assume he is using this analogy in an attempt to describe the effect in simplist terms.

It sounds like an attempt to describe it simplistically/classically. QM has a lot of weird side-effects, so people come up with all sorts of ways to visualise what happens. We're not even sure what a Schrödinger wave-function actually means; the Copenhagen model may be the easiest to grasp, but we're still not sure if it's true or not.

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"We do not require reality to conform to the expectations of the ignorant"

Probably using the analogy. Most analogies are useful for simplistic explanations. Oh, and in English, the word is borrow, not barrow. I noticed you are from Italy and this is just a piece of information. I'm assuming that English is not your first language. If it's a typo, please ignore the correction, I don't usually correct typos.

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Some try to tell me, thoughts they cannot defend,... - Moody Blues.

Neptune- The original Dark Matter.

The author feels that this technique of deliberately lying will actually make it easier for you to learn the ideas. - Donald Knuth

I find many-worlds interpretation to be much easier to grasp than the Copenhangen interpretation.

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Hello Tensor:
Actually, my first language is redneck, I'm from Alabama. That was an error, thanks for the correction. I have been reading quite a few books which do get into some QM subjects and I find that I have to put my "learned" way of thinking about the world to the side. This does make understanding easier, but not easy. Understanding these realities seems to bring into question the world we know through our five senses.

From the Heisenberg Uncertainty Principle.

The limit is h-bar (the Planck constant divided by 2xpi)

It doesn't know anything. Its position and energy are only fuzzily determined by QM. It can find itself outside the potential well because its position is determined by a probability function (the phi in Schroedinger's equation).

That's why you type so slow. \/

Diamond:
Thanks for the reply. When you say from the uncertainty principle, what physically happens? Does it borrow energy from another particle? And, I type slow because I have to look up every word I spell so I don't look like an idiot, unfortunately...

Sometimes I do, sometimes I don't. Other times, I use Bohm's.

Yes, it does. But, for me, that's what makes it all so interesting. Oh, by the way, if you need the service, I can translate Redneck (I live in rural Florida). Next week I'm even helping my neighbor get his car off the blocks. Honest, he's been painting it.

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Some try to tell me, thoughts they cannot defend,... - Moody Blues.

Neptune- The original Dark Matter.

The author feels that this technique of deliberately lying will actually make it easier for you to learn the ideas. - Donald Knuth

Jobe
When you say the many worlds interpretation, is that the multi-verse idea?
Tensor:
You know whats funny, the Italians put their cars up on blocks also. It's great, if it were not for the language and the vino (as opposed to Bud), I would feel right at home.

Ok, so the Copenhagen interpretation is that when observation occurs, the wave function collapses and one quantum state is realized.

Quoting from "In search of Shrodinger's Cat" by John Gribbin:

"Everett's interpretation is that the overlapping wave functions of the whole universe, the alternate realities that interact to produce measurable interference at the quantum level, do not collapse. All of them are equally real, and exist in their own parts of "superspace" (and supertime). What happens when we make a measurement at the quantum level is that we are forced by the process of observation to select one of these alternatives, which becomes part of what we see as the "real" world; the act of observation cuts the ties that bind alternative realities together, and allows them to go on their own separate ways through superspace, each alternative reality containing its own observer who has made the same observation but got a differetn quantum "answer" and thinks that he has "collapsed the wave function" into one single quantum alternative."

Edited to add: This is known as the many-worlds interpretation

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By the way I heartily reccomend John Gribbin's book that I quoted above. It is probably the most amazing science book I've read in my life, and goes through basic physics like light, models of the atom (bohr's etc) before plunging you into the quantum. It's readable by anyone interested, even laymen like me :P

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I'm in the middle of reading Martin Gardner's (famous for his Scientific American column of many years, Mathematical Games) latest collect of essays, I believe called Universes as Thick as Blackberries. One of the first essays is on the multi-verse idea (which relates to the book's title). He seems to go along with the multi-verse idea as a mathematical model (though I would not say he endorses it) but seems to be strongly against it as an actual physical model of the universe/multi-verse/existance.

I classify myself as an interested spectator to the debate. The one question I have about it and the debate in another thread about interactions among universes causing the big bang (I believe this was an article in a recent Discovery magazine): it would seem that if the existance of the multi-verse and of the pre-Big-Bang is unobservable and untestable, than these are just wild speculations, not theories. Or is there something in our universe that we could measure that would show the existance of such things?

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At night the stars put on a show for free (Carole King)

One Earth, One Sky - IYA 2009
All moderation in purple

Jobe:
That quote clears some problems up, I think I'll check out that book.
Swift:
I read a book by Martin Rees in which he spoke of the multi-verse. It seems very untestable to me, but interesting. I asked a question in another thread concerning gravitational fields and determining what is on the other side of an Event Horizon. If we can know something about the other side of a an Event Horizon could we know something about the other side of the singularity of the Big Bang? Ciao