Wednesday, October 20, 2010

Dunster House at Sunset

Gravitational Lensing

One of the most intriguing predictions of Einstein's theory of gravity, General Relativity, is that light rays are bent by massive objects.  For example, if two galaxies are closely lined up from our point of view, the foreground galaxy can magnify the image of the background galaxy or create multiple images, etc.   The source for the gravity of the foreground object could even be the mysterious substance "Dark matter".  Hence gravitational lensing is a tool that can tell us something about the distribution of Dark matter - see the preprint Gravitational Lensing

Quantum Theory and Relativity

There are subtle issues with the compatability of the two workhorse theories of contemporary physics:  special relativity and quantum mechanics.  The EPR paradox from the 1930's (the E stands for Einstein)  and Bell's Theorem from the 1960's are two of the classic examples.  The weight of suspicion often tends to fall on the quantum side.  Einstein, notably unenthusiastic about the fundamental role of probability in quantum mechanics,  believed that "God does not throw dice".  John Bell, when asked if quantum mechanics could be wrong replied, "I hesitated to think it might be wrong;  but I knew it was rotten".  Nonetheless quantum mechanics has turned out to be fantastically accurate and the basis for much our current understanding of matter and radiation - likewise for special relativity.  The preprint Can quantum theory and special relativity peacefully coexist? discusses the issues.