# Sun earth distance

1. Jul 24, 2008

### Zman

How is the sun earth distance currently determined?

I read about a method where the distance between the earth and mars is determined when they are in opposition using parallax.
Knowing the orbit period of both mars and the earth, Kepler’s third law is then used to determine the earth sun distance.

Is this method seen as the best or is a different method used?

2. Jul 24, 2008

### pixel01

I do not know if that's the best, but I think there another way.
First we can calculate the mass of the Earth via the period of the Moon and its distance from the Earth. Then identify the angular velocity of the Earth around the Sun by directing to the faraway galaxies or stars at exactly one moment at night, say at 0:00

3. Jul 24, 2008

### D H

Staff Emeritus
Last edited by a moderator: May 3, 2017
4. Aug 6, 2008

### Zman

Thanks D H for the reference to the Quest for the AU article. The history was very interesting and it answered my question which is that Radar is the technique used today.
Its only about 5 mins for the radar pulse to return from venus at closest approach.