
Despite perihelion in January, max speed around Sun was on Xmas day. - ColinWright
http://twitpic.com/838m7v
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ColinWright
This graph shows the different effects on the Earth's speed around the Sun.
It's complicated.

Perihelion was at 1am GMT 5 Jan.[1] However, the Earth and Moon orbit a common
center of gravity[2], and when the Moon is closer to the Sun than the Earth,
the center of the Earth is moving marginally faster than when the Earth is
closer to the Sun than the Moon.

The Moon travels about 1 km/s in orbit (Earth relative)[3], the Earth–Moon
mass ratio is about 81:1[4], and the distance to the Moon is about 60 Earth
radii.[5]

References:

[1] <http://1.usa.gov/AykBoB>

[2] <http://en.wikipedia.org/wiki/Center_of_mass#Astronomy>

[3] <http://www.freemars.org/jeff/speed/index.htm>

[4]
[http://en.wikipedia.org/wiki/Orbit_of_the_Moon#Double_planet...](http://en.wikipedia.org/wiki/Orbit_of_the_Moon#Double_planet.3F)

[5] <http://en.wikipedia.org/wiki/Orbit_of_the_Moon>

