If the distance between earth and moon is doubled then gravitation force between them is 1/4.That's all.

Effect of Distance on Gravitational Force
When the distance between two objects increases, the gravitational force between them decreases. This is because gravity follows an inverse square law, which means that the force decreases as the square of the distance increases.

Calculation of Gravitational Force
The formula for calculating the gravitational force between two objects is F = G(m1m2)/r^2, where F is the force, G is the gravitational constant, m1 and m2 are the masses of the two objects, and r is the distance between them.

Scenario: Distance between Moon and Earth Doubled
If the distance between the Moon and the Earth is doubled, the value of r in the equation above will be doubled as well. Therefore, the gravitational force between them will decrease by a factor of four. This means that the Moon will experience only one-fourth of the gravitational force from the Earth compared to its previous value.

Impact of Decreased Gravitational Force
The decrease in the gravitational force between the Moon and the Earth will have several impacts:

- The Moon's orbit around the Earth will become weaker and more elliptical, which means that the Moon's distance from the Earth will vary more than before.
- The tides on Earth will be weaker, as the gravitational force of the Moon is responsible for creating tides. This could have an impact on coastal ecosystems and human activities that rely on the tides.
- The Moon's gravitational pull on the Earth will also be weaker, which could affect the Earth's rotation and tilt. However, this effect is likely to be very small.

Overall, doubling the distance between the Moon and the Earth would have significant effects on the gravitational force between them, which could have consequences for a range of natural phenomena.