Tuesday, August 24, 2010

Nicole Oresme

Nicole Oresme was a sophisticated 14th century French philospher. He discussed and compared Earth-centered and Sun-centered models of the solar system and couldn't find any way to dismiss the Sun-centered model - though he personally didn't believe it. He also used techniques which were very close to Cartesian coordinate systems - over two hundred years before Descartes. See the Nicole Oresme article in the Stanford Encyclopedia of Philosophy.


Transient Radio Neutron Stars preprint.
Here I will review the high time resolution radio sky, focusing on millisecond scales. This is primarily occupied by neutron stars, the well-known radio pulsars and the recently identified group of transient sources known as Rotating RAdio Transients (RRATs). The RRATs appear to be abundant in the Galaxy, which at first glance may be difficult to reconcile with the observed supernova rate. However, as I will discuss, it seems that the RRATs can be explained as pulsars which are either extreme nullers, highly variable or weak/distant. I will re-cap some recent results including a re-analysis of the Parkes Multi-beam Pulsar Survey, which has identified several new sources, as well as the unusual timing behaviour of RRAT J1819-1458. This leads to an examination of where RRATs fit within the evolution of neutron stars post-supernova.

Measuring the mass of solar system planets using pulsar timing

Measuring the mass of solar system planets using pulsar timing
Apparently the pulse time of arrival from pulsars is so accurate it can help determine the masses of the planets of the solar system with accuracy comparable (or better) than data from spacecraft missions. That's because the motions of the other planets cause the Earth to wiggle in its orbit. The pulsar data allowed the researchers to determine the Earth's orbit so well, it could be used to determine the masses of the other planets!
See also Pulsar Signals Could Reveal Solar System Secrets at Science.