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location United Kingdom
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visits member for 3 years, 5 months
seen Nov 23 at 19:43

I live in Essex, England.


Sep
29
accepted Great circles on a unit sphere
Sep
29
comment Great circles on a unit sphere
Bravo! The final equation in your excellent answer confused me. I've just worked out the equation for a point on the equator with a tangent vector along the $x$ axis and out pops the equation for the equatorial great circle.
Sep
28
comment Great circles on a unit sphere
Thanks. Excuse my hopeless vector algebra but how would that work with, for example, a point on the “north pole” $<x_{0},y_{0},z_{0}>=<0,0,1>$ and with a tangent vector $\vec{u}=<1,0,0>$ along the $x$ axis, which should give a great circle on the $xz$ plane? I can't see how that great circle pops out of your equation.
Sep
27
revised Great circles on a unit sphere
Added "spherical-geometry" tag
Sep
27
comment Great circles on a unit sphere
Doesn't that question assume you know more than one point on the suface? I was hoping for an answer for just one point.
Sep
26
asked Great circles on a unit sphere
Sep
24
awarded  Autobiographer
Sep
21
comment Confusion regarding Riemann normal coordinates
@Semsen Why did you delete your answer and my subsequent comments? With your help I thought I was on the brink of answering my question. I'm puzzled.
Sep
21
revised Confusion regarding Riemann normal coordinates
added 1718 characters in body
Sep
18
revised Confusion regarding Riemann normal coordinates
Still trying to figure out the metric
Sep
18
revised Confusion regarding Riemann normal coordinates
Partial attempt to answer my own question
Sep
18
comment Confusion regarding Riemann normal coordinates
@wspin Thanks. That bit is now clearer. Is $\theta=\sqrt{\xi^{2}+\eta^{2}}$ a necessary condition for Riemann normal coordinates? Any chance of a hint as to how the metric is derived?
Sep
18
comment Confusion regarding Riemann normal coordinates
I just can't see how they derive the $=\frac{d\xi^{2}}{\theta^{4}}$ etc metric from the information given.
Sep
17
asked Confusion regarding Riemann normal coordinates
Sep
6
awarded  Popular Question
Sep
6
comment Geodesic deviation on a unit sphere
Because both particles are following geodesics along lines of longitude. I'm a self-studier by the way, so apologies if I've got this completely wrong.
Sep
5
comment Geodesic deviation on a unit sphere
Thanks. @XipanXiao - does that now make more sense?
Sep
5
revised Geodesic deviation on a unit sphere
inserted a link to equation of geodesic deviation
Sep
5
awarded  Editor
Sep
5
revised Geodesic deviation on a unit sphere
deleted 1 character in body