Re: speed of light

[Leigh Palmer <palmer@SFU.CA>]

> Has anyone looked for a reflected supernova flash off adjacent
> stellar objects? (It would have to be a glancing reflection,
> I imagine if one had the ..er.. 1988 event in mind?)

As the light from the SN1987A event expands in a spherical shell
it illuminates the surrounding interstellar medium. By doing the
geometry* (and trigonometry) on what should be seen at Earth of
this reflection nebula you will see that an expanding circle of
illumination should surround the star. It does (it has been
observed) and it expands in time as expected. There is a real
bonus to this. By measuring the apparent angular diameter of the
illuminated circle one can get a geometric distance to the
object directly without resorting to any "distance ladder" or
"standard candle" arguments. The determination of distance is as
good as the accuracy that can be obtained in measuring the size
of the circle.

Neat, eh?

Leigh

*Think about a sphere and an ellipsoid with the Earth at the
other focus. Near the supernova the ellipsoid is
indistinguishable from a paraboloid, but you will see a pretty
neat geometry.