Relativity wins again

GuanYin

General relativity theory has stood up to another experimental test.

It seems that radiosignals sent to the Cassini spacecraft that is Saturn bound were distorted by the suns gravity as the theory suggested.

Anyone know what other tests were used?

dudara

A friend of mine recently defended his PhD thesis. The e-mail sent out announcing the public talk was as follows

'Gravity on Conformal Superspace'

Abstract
The configuration space of general relativity is superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms. However, it has been argued that the configuration space for gravity should be conformal superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms and conformal
transformations. Taking this conformal nature seriously leads to a new theory of gravity which, although extremely similar to general relativity, contains some striking new features. One particular consequence of the theory is the apparent resolution of the cosmological constant problem and this will be the focus of this talk.

Now, if that doesn't do your head in, what will??

It's seems that there is still a lot of work to do with relativity. It passes a lot of tests, but there is still a lot of disagreement over the underlying mathematics.

GuanYin

Everytime I read something in physics like that, I console myself with Niels Bohr's comment about quantum theory.

He said that "if a person isn't outraged on first hearing about quantum theory, he didn't fully understand what was being said".

dudara

I decided a long time ago not to think too hard about quantum mechanics and just apply it when I'm working. I can philosophise about it later.

All the different interpretations and the basic assumptions you are asked to make are confusing and go against everything you experience in the macroscopic world, but the fact is quantum mechanics works, even if in a very ad hoc fashion.

I often give grinds to first years honours students in Physics, and they have huge difficulty with quantum mechanics and who can blame them.

There are two great chapters about the foundations of quantum mechanics in a book called "It must be beautiful: great equations of modern science" by Graham Farmelo. It put a really great personal spin on the story and the difficulties that the likes of Einstein, Bohr, Schrodinger and Heisenberg had with the concepts of quantum mechanics.