If earth were twice as far from the sun, the force of gravity attracing earth to the sun would be

The gravitational force between two objects of mass m₁ and m₂ if

where d =  distance between the objects
G = gravitational constant

We could consider the earth and the sun as the two masses.
If the earth were twice as far from the sun, then the distance would be 2d.
Therefore the force of attraction would be


The force of gravity will decrease by a factor of 4.