# About the Earth's orbital velocity

1. Dec 17, 2008

### mazen_zone

i want to know if the earth change its orbital velocity along the day?

as i heard that due to its elliptical shape the distance between the earth and the sun slightly change during the day (increase then decrease again) ,so the orbital velocity also has to change to compensate this change in distance...

2. Dec 17, 2008

### Janus

Staff Emeritus
Not over the course of a day, but over the course of a year the Earth's orbital velocity varies as its orbital distance varies.

3. Dec 17, 2008

### tony873004

It does, although based on the context of your question, it seems like you are referring to speed, not velocity. So this is just a small nit-pick of your use of the word 'velocity'.

Velocity is a vector quantity, so direction must be taken into account. Every day, our direction changes by nearly 1 degree. It's our orbital speed that doesn't change much during the course of a year. It takes about 6 months go go from minimum speed of about 29 km/s to maximum of about 30 km/s, so over the course of a day, there is not much change.