sci.physics

On 2008-02-17, Quadibloc wrote:
> On Feb 16, 12:23 pm, Sam Wormley wrote:
>> This distance was
>> obtained geometrically using a light echo technique.
>
> But all that surrounding dust might, possibly, have disturbed the
> *period* of that Cepheid, so as to make that particular type of
> measurement less useful than one might desire in creating a cosmic
> yardstick.

But what is different about this method is that the period of the
Cepheid is irrelevant to the distance calculation. It could equally
well be applied to any varying light source. The method hinges on
measuring the time difference between variations in brightness of
the star and those same variations in the refected light of a point
in the surrounding dust.

From the time difference a distance between the two can be calculated
and from there the distance to Earth obtained with simple trig.
There are one or two points that come to mind that the paper doesn't
address but it sounds like it could be extremely accurate when the
conditions allow this method to be used.

--
Andrew Smallshaw
andrews@