Arcadian Functor

occasional meanderings in physics' brave new world

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Marni D. Sheppeard

Friday, October 20, 2006

Jordan and Pizza

The volume The Physicist's Conception of Nature, edited by Mehra, is a collection of lectures given at the 70th birthday celebrations for Dirac in 1972. The list of contributors is impressive: Chandrasekhar, Dirac, Wheeler, Heisenberg, Wigner and Schwinger, to name a few.

Pascual Jordan's contribution is entitled The Expanding Earth. He explains that, having been deeply impressed with Dirac's 1937 idea of a varying G/c^2, he spent time investigating the possibility that the Earth had been expanding over time. The lecture includes some beautiful geological diagrams regarding mid-ocean drift, and he talks about the difficulty that Wegener had with geologists accepting the theory of continental drift. Now we understand that the value of G/c^2 is decreasing as we go back in time, and consequences of this should indeed be measurable on Earth. Jordan says:

There exists a great diversity between the mentalities of physicist's and of geologists. Physicist's are eager to learn about new facts and new ideas caused by new facts.

Pascual Jordan is one of the founders of Jordan algebras, which appear in M theory.

For anyone who happens to be around Sydney next week: come to the Feynman fest at the University of Macquarie at 5.30 pm on Wednesday Oct 25 for free pizza!


Blogger nigel said...

Hi Kea,

I won't be Australia on Wednesday, but I hope it goes well. Dirac's ideas are always fascinating. Dirac had the idea that G falls with time, which is interesting but wrong (actually G rises in direct proportion to the age of the universe, as shown by gravity mechanism based on Yang-Mills radiation exchange, although that only has limited effects on cosmology and astronomy, eg, it doesn't affect the brightness of stars at all because the increased gravitational compressive force in stars is simply offset by increased electromagnetic repulsion between protons, due to the fact that electromagnetism and gravitation are different aspects of the same thing). Unfortunately, free thinking and especially causality is virtually a heresy in physics now.

Dirac on the Dirac sea:

‘... with the new theory of electrodynamics we are rather forced to have an aether.’ – P.A.M. Dirac, ‘Is There an Aether?,’ Nature, v.168, 1951, p.906.

Best wishes,

October 23, 2006 2:38 AM  
Anonymous Kris Krogh said...

Hi Kea,

"Now we understand that the value of G/c^2 is decreasing as we go back in time, and consequences of this should indeed be measurable on Earth."

What references did you have in mind there?

Many thanks,

Kris Krogh

October 24, 2006 7:10 PM  
Blogger Kea said...

Hi Kris

Just follow this blog back and check out some of the cool links.


October 29, 2006 4:33 PM  

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