In article ,
Igor writes:
Check out this link:
http://www.newtonphysics.on.ca/Anoma...eleration.html

It's an interesting idea. While I didn't check the calculations in
detail, the method looks correct, and it certainly appears to produce
an upper limit for the density of the Kuiper Belt of 1.4E-19 g cm^-3.

What I wonder is how reasonable that density is. It seems awfully
high to me. At a "normal" gas to dust ratio of 100, that's about 8E6
hydrogen atoms per cubic centimeter. I suppose one could argue that
the gas is depleted, or maybe this density is reasonable. Anybody
able to comment?

One clear mistake in the web page is the assertion that the IRAS data
show the Kuiper Belt. Dust in the KB is far too cold to have been
seen by IRAS. The IRAS data sample the Zodiacal cloud roughly 1 AU
from the Sun. (Of course the data average over a range of
distances.) That's why the data are depicted as blue in the figu
they represent the 12 micron observations.

COBE produced much better data on the Zodiacal cloud, leading to
detailed models. However, not even the COBE data detect dust at the
KB distance from the Sun. The expected temperature is roughly 75 K
at 30 AU.

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Steve Willner Phone 617-495-7123
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