On Wolfram Alpha, I get the following values for gravitational acceleration on earth due to the sun and moon, respectively: gravitational constant * mass of sun / (distance to sun)^2 → 0.005991 m/s2 gravitational constant * mass of moon / (distance to moon)^2 → 3.68×10-5 m/s2 If the Earth's gravitational acceleration vector is 9.8 m/s2 toward the Earth's center of mass, I'm trying to determine how much that vector is changed by the presence of the sun or moon. I think I can just say that there's a point on Earth where the Sun's 0.005991 m/s2 vector would be orthogonal to the Earth's 9.8 m/s2 vector so that I can find the angle between the Earth and Earth+Sun vector as: Inverse Tan(.005911 / 9.8) → 0.03456° Q1: Is this correct? It is a larger angle than I was expecting. Q2: On a tangent, why is the moon primarily responsible for tides when the sun's gravitational acceleration at Earth is greater? Is it because the slope of 1/r2 is flatter for the Sun than it is for the moon at the distances involved?