How did scientists determine how fast earth's orbit is around the sun?

1 Answer
Feb 22, 2016

Answer:

The orbital speed of the Earth is easy to calculate using geometry - we can find the circumference (distance) and divide it by a year (time)

Explanation:

The Earth completes one full orbit, #360^@#, in one year, which is 365.256 days, or exactly 31,556,926 seconds.

The Earth's orbit is slightly elliptical, but is pretty close to circular. The mean (semi-major) distance from the sun to Earth is 149.6 million km. Remembering our geometry a circle with a radius of 149.6 million km is:

#c=2 pi r#
#c=2*pi*149600000 km#
#c= 939964522 km#
or
940 million km.

the orbital speed can be calculated using:
#v=d/t#
#v=(940000000km)/(31556926s)#
#v=29.79 (km)/s#