The Moon has a smaller mass than the Earth and so the pull of gravity by the moon on an object is smaller than on the earth. The moon has a smaller gravitational field strength. On the Moon ...

How is matter different from mass? These and other questions about the deepest levels of physics, answered inside.

For example, a helium atom has an atomic mass of 4, but an atomic number (or positive charge) of 2. Since electrons have almost no mass, it seemed that something besides the protons in the nucleus ...