SETI again

On 7/28/06, Robert wrote:
(...)
> depends on how reflective it is. i believe it was only one pixil in
> size.

Sedna's albedo is 0.25 . It has an estimated diameter of 1700 Km
(larger than Texas, for sake of comparisons). It appears as something
4 pixels wide in the pictures. An object of corresponding reflexivity
one pixel wide would still be 435 Km wide. In order to a
locomotive-sized object (say 10 meters wide) to be as bright as an
object 435 Km wide with an albedo of 0.25 , it would need an albedo of
7,3x10^9 .

Unfortunately albedo beyond 1 are physically impossible, for that
would mean a miraculous object that reflects more light than it
absorbs. In the case of the huge albedo found above, your "locomotive"
would put the brightest quasars in the Universe to shame.

> some how they came up with the determination of "likely to be as
> small as a locomotive"
(...)

As you can see from the simple calculation above, somehow they made an
error of nine orders of magnitude at some point.