How fast is our Earth orbiting the Sun? We all know that the Earth takes one year to orbit the Sun, but do we know what speed this corresponds to? This is an easy value to calculate and is in some ways similar to the rotation speed calculation.
Two values are required to determine this value. The first is the Earth's average distance from the Sun:
a_{Earth}^{ }= 149.598261 x 10^{6} km
The second value is the Earth's orbit period, which we know is one year. What exactly is one year in days, hours, etc.?
The "sidereal year" is determined by the time required by the Earth to return to the same position in its orbit. This value can easily be looked up:
T_{orbit}^{ }= 365.256363004 days = 8766.1526 hours
The circumference of the Earth's orbit can now be calculated using the following equation:
C_{Earth} = 2πa
C_{Earth} = 9.4 x 10^{8} km
The velocity that the Earth has while in orbit can now be calculated using the circumference of the Earth's orbit and the time required to travel this distance:
v_{orbit} = C_{Earth} ÷ T_{orbit}
v_{orbit} = 107,225 km/h = 29.78 km/s = 87 times the speed of sound
Wow! This speed is approximately 91 times faster than Earth's equatorial rotation speed! Although this sounds really fast, this speed is only 1/10000th the speed of light.
This value is actually the average orbit speed that the Earth moves in its orbit. The Earth's orbit is not perfectly circular, so its speed varies slightly over the year. It is at its fastest around January 3 and at its slowest around July 3.
Below is a table of the average orbit speeds of the major Solar System bodies: The Sun is not included here because it is the parent body and therefore does not orbit in this ideal case.
BODY | a_{orbit} (km) | C_{orbit} (km) | T_{orbit} (hrs) | v_{orbit} (km/hr) |
MERCURY | 5.79091 x 10^{7} | 3.639 x 10^{8} | 2,111.2584 | 172,362 |
VENUS | 1.0820893 x 10^{8} | 6.79896 x 10^{8} | 5,392.8166 | 126,074 |
EARTH | 1.49598261 x 10^{8} | 9.4 x 10^{8} | 8,766.1526 | 107,225 |
OUR MOON | 384,399 | 2.415250x 10^{6} | 655.718 | 3,683 |
MARS | 2.279391 x 10^{8} | 1.43218x 10^{9} | 16,487 | 86,866 |
CERES | 4.13832587 x 10^{8} | 2.6 x 10^{9} | 40,332 | 64,465 |
JUPITER | 7.785472 x 10^{8} | 4.89175 x 10^{9} | 103,958 | 47,055 |
SATURN | 1.43344937 x 10^{9} | 9.0066 x 10^{9} | 258,221 | 34,879 |
URANUS | 2.876679082 x 10^{9} | 1.80747 x 10^{10} | 739,178 | 24,452 |
NEPTUNE | 4.503443661 x 10^{9} | 2.82959 x 10^{10} | 1.44456 x 10^{6} | 19,588 |
PLUTO | 5.906376272 x 10^{9} | 3.71108 x 10^{10} | 2.1747193 x 10^{6} | 17,065 |
ERIS | 10.12 x 10^{9} | 6.35858 x 10^{10} | 4.8864 x 10^{6} | 13,013 |
Rotation Speed was Last Updated on December 08, 2010 |