sci.physics

"Andrew Smallshaw" wrote in message
news:@...
| 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.
|

/Copernicus/