You're correct in your understanding of how gravitational force works and the implications of increasing the moon's size and mass. The gravitational force \( F \) between two objects is described by Newton's law of universal gravitation, represented by the formula:
\[ F = G \frac{m_1 m_2}{r^2} \]
where:
- \( F \) is the gravitational force between the two masses,
- \( G \) is the gravitational constant,
- \( m_1 \) and \( m_2 \) are the masses of the two objects (in this case, the Earth and the moon),
- \( r \) is the distance between the centers of the two masses.
If the moon were to double in size, its volume would increase, and assuming it maintains the same density, its mass would also increase significantly. Specifically, if the radius of the moon doubled, the volume (and therefore mass, at constant density) would increase by a factor of \( 2^3 = 8 \). This means the moon's mass could potentially increase by roughly a factor of 8.
With the increased mass of the moon, the gravitational force between the Earth and the moon would increase as well. Even though the distance \( r \) between their centers remains the same, the increase in mass (\( m_{\text{moon}} \)) would lead to a stronger gravitational pull on Earth.
This intensified gravitational interaction could have several implications, including:
- Greater tidal forces, leading to more extreme tides.
- Potential geological impacts on Earth, depending on the increased gravitational effects.
- Possible alterations to the Earth's rotation and axial tilt over long periods due to the changes in gravitational interactions.
Overall, doubling the size of the moon while maintaining its position would indeed have significant gravitational effects on both the moon and the Earth.