Quantum Entanglement

Some previous discussion on this forum follow:

On space and the universe in general
http://www.able2know.com/forums/viewtopic.php?t=9335&postdays=0&postorder=asc&start=0

On string theory in particular
http://www.able2know.com/forums/viewtopic.php?t=14300&highlight=string+theory

I'll be checking out your links.....

You are mixing three different ideas here.

Quantum entanglement is the fact that two particles can be linked by a single wave function. Two particles, for example, have different spin numbers it is gauranteed that one is positive and one negative. However these states are not determined until they are observed. As soon as you observe that one is positive the other "becomes" negative.

This is hard to describe well without a background of the math. But Quantum entanglement has been shown experimentally and is widely accepted as scientific fact.

Einstein did an experiment (the photoelectric effect) that inspired Quantum theory, but had nothing further to do with it. He actually objected to Quantum theory for a while saying "God does not play dice with the Universe".

String theory is just a conjecture. It has not been proven or disproven. We don't know how to test it yet, but it is a very interesting idea.

If two electrons meet
don't they just Like each other?

Ok, thanks for clarifying that up. Quantum Entanglement is definately what I am interested in.

For example, could one electron be twenty miles away from it's "mate" and still move in tandem?

First a brief DISCLAMER:

Quantum Mechanics is very strange. The laws of physics at this level are quite a bit different than you are accustomed. However Quantum Physics is almost universally accepted as "true" by the scientific community. It has met the scientific criteria of being proven meaning it has been rigorously tested and there is no alternative that scientists consider reasonable.

One of my pet peeves is that people pick up on "taglines" about scientific principles without understanding the science or mathematics behind them. I would like to avoid this.

To truly "understand" Quantum Physics you need to understand the Math and the experiments that have been done to show this math is valid (i.e. describes nature).

end DISCLAMER

Quantum Entanglement can effect two electrons that are twenty miles away.

However to say they "move in tandem" is not at all correct.

In real physics, a partical has either a positive "spin" or a negative spin. Either one or the other. Furthermore two particles can be paired. One is positive and one is negative.

Quantum Mechanics says that particles (e.g. electrons) can exist in an "indeterminant state". That is that the Universe has not decided yet whether this partical has a positive or negative spin. Of course if one partical of a pair is indeterminant, the other must be too since if the other is negative, the first must be positive.

So one indeterminant electron in a pair means they both are indeterminant.

Here is the weird part. When you "observe" (i.e. measure) a particle, it at that instant becomes either positive or negative. Somehow the act of "observing" fundamentally changes the partical. It is like the electron doesn't make up its mind what it's spin is until you look at it.

Let me emphasize that this is very strange and nearly impossible to believe. If you are saying to youself "That can't be right" then you are getting it.

The Entanglement is this. If you observe one electron and see it is positive spin, the other paired electron "becomes" negative spin even if it is twenty miles away. It is *not* correct to say that the other electron was always negative but we just didn't know it. Literally, the process of "observing" somehow forces both electrons to "make up their minds" at that instant, and they are guaranteed to have opposite spins.

Now my lucid and brilliant prose is necessarily lacking. I am trying to describe a phenomina that physcist express precisely with mathematics using words. English is remarkably inadaquate to express these things. This is the reason that I need to talk about electrons making up their minds. I hope that I got these very strange ideas accross.

Quantum Entanglement - and Quantum Mechanics in general has be shown by experiment. If you are interested in gaining a pretty good understanding of QM without getting a physics degree, I would highly recommend the book

"In search of Schrodinger Cat"

by John Gribbon. He does a very good job at explaining the very strang ideas, and the experiments they are based on. It also is a very good story about physicists wrestling to find the truth.