The correct response is:
The gravitational force between Earth and the Moon would go down by a proportional amount.
According to Newton's law of universal gravitation, the gravitational force \( F \) between two masses \( m_1 \) and \( m_2 \) separated by a distance \( r \) is given by the formula:
\[ F = \frac{G \cdot m_1 \cdot m_2}{r^2} \]
If the distance \( r \) between the Earth and the Moon doubles, the new force \( F' \) would be:
\[ F' = \frac{G \cdot m_1 \cdot m_2}{(2r)^2} = \frac{G \cdot m_1 \cdot m_2}{4r^2} = \frac{1}{4} F \]
Thus, the gravitational force would be reduced to one-fourth of its original value, meaning it goes down by a proportional amount.