[LEAPSECS] Nit-pick: SI second

Rob Seaman seaman at noao.edu
Thu Feb 10 18:17:49 EST 2011

Oooh! Google "Sagnac" and you also get lots of trendy pseudoscience from sites like anti-relativity.com. What fun!

On Feb 10, 2011, at 4:01 PM, Mark Calabretta wrote:


> On Thu 2011/02/10 07:18:53 -0800, "Tom Van Baak" wrote

> in a message to: "Leap Second Discussion List" <leapsecs at leapsecond.com>


>> Yes, the radius of the earth is slightly dependent on latitude,

>> perhaps that's what you're thinking about. But a clock at sea

>> level at lat 0 will run the same as and a clock at sea level at

>> lat 45 or lat 90 because that's what MSL is - the equipotential

>> surface of the geoid.


> A clock at the equator has a tangential velocity of 500m/s

> whereas for one at the pole it is 0m/s. The difference,

> amounts to about 100ns/day as per your later calculations.

> This is the Sagnac effect of Special Relativity.


> Regards,

> Mark Calabretta

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