Friday 6 April 2012

It's all in the spin

Electron spinning in hydrogen
Try this one out for size... the next time you have a clear night and can see the stars. Go out into your garden and stand there, your arms resting by your sides. Look up at the stars. Now start spinning. The stars spin around you AND your arms start to move away from your body. If you spin fast enough your arms will be straight out.

It could be that the spinning of the stars and the motion of your arms is just coincidence or may be there is some underlying physics connecting the two.

This may seem a bit if a silly idea, the stars and galxies having an effect on my arms when I start to spin. It just doesn't seem to make sense. It makes more sense that it is likely to be some interaction with the earth than the stars, after all that would be more immediate.

The idea mentioned here is known in the trade as Mach's principle, also, Mach's conjecture. It was given this name by Albert Einstein. Mach was convinced that there is indeed a physical law which binds the motion of distant stars to a local inertial frame, us standing in the garden.

Einstein used some of the ideas of Mach's to help him in his development of his theories of relativity.

With spin you can actually over come gravity in your back yard. Take a bucket and half fill it with water. Now swing it from side to side, start small and gradually make the swings bigger.When you feel brave enough let the swing go right over the top. You can now rotate the bucket through full circles without the water falling out.

The water is stuck in the bucket even when the bucket is directly over head and there is nothing to stop the water falling out. Now stop. Turn the bucket upside down and the water comes pouring out because of gravity. So we have to conclude that the spinning motion over comes gravity.

This method of over coming gravity is explained using the idea of inertia or ficticious forces and they are covered in a post on non-intertial frames of reference. They are called ficticious because they disappear as soon as the bucket stops spinning.

Spinning is not only limited to large scale, or macroscopic, phenomena. When we make observations on a tiny scale the idea of spin once again comes into play. When quantum mechanics started there were a number of issues that needed to be addressed to reconcile theory with experiment and one of these was the idea of electrons, protons and other sub atomic particle having spin.

A Gyroscope
But hold on a second, we know that when we get down to quantum mechanics things get odd, in a way this is true of spin at a quatum level. Electrons can have spin, but they do not spin faster or slower. They can be made to behave a little like a gyroscope by placing them in a magnetic field. In the same way that a gyroscope can precess and electron will have similar behaviour in a magnetic field and it is this that is exploited in Nuclear magnetic resonance (NMR).

At a quantum level spin is vital to existing theories.

Now lets think this through for a minute, from the massive to the miniature everything spins. Galaxies spin, the stars in galaxies spin, our sun spins, the earth spins, the electrons spin, protons spin, quarks (if they exist) are thought to spin. Light sort of spins as it goes charging through space.

Spinning tops stand upright when they spin, gyroscopes spin. Although we don't think we spin we are actually standing on a planet that spins on it's axis as it orbits a sun that spins and so on.

It appears that angular momentum associated with spin is conserved just like linear momentum.So spinning is important.

Coming back to the idea of standing in my garden spinning round with my arms in the air. Is there really something profound about all this spinning? By spinning am I genuinely interacting with every star and galaxy in the universe? I actually really like that idea.

Simply by spinning round I am touching and being touched by the entire universe and if God is the universe then you are touching God himself? I like that idea as well.





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