The Lumpy Universe

Posts on a variety of topics of interest, including current events, politics, economics, technology, science, religion, philosophy, and whatever else comes to mind. Not affiliated with The Lumpy Universe at NASA/Goddard (sorry--I just happen to like the name).

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06 March 2010

Particle Entanglement

Particle entanglement is a phenomenon in quantum physics whereby two electrons are somehow associated with each other in a way that does not seem at all intuitive. The two electrons of such a pair have opposite "spin". If the spin of one of the electrons is reversed, the spin of the other will also reverse - regardless of the separation between the two. This seems rather strange to us.

Perhaps it's a phenomenon of additional dimensions. To illustrate, consider the 2-dimensional world called Flatland. As a 3D being, you are able to observe Flatland without being observed yourself. Let's say you take a piece of tubing and fashion a circle out of it, and drop it into the plane of Flatland. The circle residing in the plane of Flatland will appear as a solid circle to the Flatland inhabitants on the outside of the circle, or as a solid circular exterior wall to inhabitants inside the circle.

Now tilt the circle so that the plane of the circle is perpendicular to the plane of Flatland, and the plane of Flatland bisects the circle. The intersection between the circle and Flatland will now consist of two points. The size of the points is the cross-section of the tubing from which the circle is constructed.

Picture the situation where the two points are moved apart. This results in enlargement of the circle, or perhaps an excursion of the circle up and down relative to the horizontal plane of Flatland, but the two points are still physically connected in the larger 3D universe.

Add spin to the tubing from which the circle is constructed, but not to the circle. To the observer in Flatland, the two points they can observe will be spinning in opposite directions. If the Flatlander somehow grabs one of the points and reverses the spin on that point, the spin on the other point will also reverse.

So there you go. Maybe the key to understanding entanglement is by venturing into additional dimensions.