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-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
bounces@carnot.physics.buffalo.edu] On Behalf Of Bill Nettles
Sent: Thursday, February 19, 2009 11:54 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] Figuring Physics in the March TPT The Physics
Teacher
Okay, now I see it. I still think the diagram is poorly made, but the end
of the first sentence should say, "depends (as a first approximation) on
the ratio of the sphere's diameter to the distance from the sphere." or
something like that. Yeah, subtended angle (which is what he highlights
in the 2nd sentence) depends on more than distance.
Bad Astronomy had a good picture of a planetary nebula that was 2 AU
across at a distance of 500 LY. It was kind of fuzzy, not nearly as
pretty as some Hubble pictures of other planetary nebula, but they were
4.3 LY across at 10000 LY distance. but when you compare the angular
sizes, the quality of the first becomes dramatically impressive (13
milliarcseconds versus 1.5 arc-minutes).
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