so the earth is twice as big, but the same mass? seems like there are some detectable changes there. but maybe you're increasing mass in a really tricky way. it'll need to be more than double to have the same effect. at a given distance.

The other one that seems like it would be tough is strength of a magnetic field. inverse cube law, rather than inverse square. seems really hard to do something and get the same answers.

i'm an idiot. by distance you mean something more like a pure scalar value. if you double all the secret constants in the universe, we can't tell the difference.

You double k1 and k2. Now something involving k1*k1/k2 is twice it was before.