How to calculate gravity ?

force of gravity = mg is the formula to follow.

m=mass of the object, and g=acceleration

so multiply mass and acceleration :)

use the formula: force of gravity = mg

Explanation:

In order to properly calculate the gravitational force on an object, this equation takes into account the masses of both objects and how far apart the objects are from each other. The variables are defined below. The masses of objects need to be in kilograms (kg) and the distance needs to be in meters (m). You must convert to these units before continuing with the calculation. If you are trying to calculate the force of gravity between an object and the earth, you need to determine how far away the object is from the center of the earth. Once you have defined the variables of your equation, you can plug them in and solve them. Be sure that all of your units are in metric and on the right scale. Mass should be in kilograms and distance in meters. Solve the equation using the proper order of operations. You are welcome ;)

i believe the answer is a

3. dark matter

empty space could also be a simple vacuum