From: J. Andrew Rogers (email@example.com)
Date: Sun Dec 07 2003 - 17:49:43 MST
On 12/7/03 3:33 PM, "Eliezer S. Yudkowsky" <firstname.lastname@example.org> wrote:
> While reviewing 2003, I ran across this article, which describes
> humanity's creation of yet another Artifact like the Clock of the Long
> Now. The key point is highlighted in the article's body for your convenience.
> "It's probably the roundest item ever made by hand. 'If the earth were
> this round, Mount Everest would be four meters tall,' Dr. Nicolaus said.
> An intriguing characteristic of this smooth ball is that there is no way
> to tell whether it is spinning or at rest. Only if a grain of dust lands
> on the surface is there something for the eye to track."
Actually, the most perfect sphere that I am aware of was the superconducting
Niobum-coated quartz sphere used in the Gravity Probe B physics program
(which hardly anyone has heard of). Expanded to earth size, the tallest
feature of the sphere would be in the 2-3 meter range, depending on who you
The sphere was part of the most perfect gyroscope ever made by several
orders of magnitude, and it was designed to detect relativistic frame
dragging, which was theorized but never measured until GPB. The gyroscope
was designed to run continuously for a couple years at 10,000 rpm with an
average drift of 10^-12 degrees per hour -- very impressive precision.
Trivia known to me only because I was very tangentially associated with the
program many years ago when working for the DoD. Google turns up
appropriate references to the science program and even has pictures of the
sphere and gyroscope.
-- J. Andrew Rogers (email@example.com)
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