Mass is a confusing concept to a lot of people who accidentally confuse it with "weight." While we do tend to give the units of mass in the same parameters that we give weight, mass is simply defined as how much matter an object contains. Weight, on the other hand, is really just a measure of how much gravity is enacted on an object, or even more simply, how much force the Earth's gravity is using to pull down on an object.
Therefore, the amount of mass of an object doesn't change, even if we somehow change the gravity (such as if we took the object to the moon). On the moon, the object's weight would change, but its mass would still be the same.
If we were able to bring the same object-such as a ten-pound bowling ball, whose mass based on industry standards for a regulation ball is about 7.5 kg-to each of the other planets in our solar system, here's how the weight would be affected:
Mercury – 3.7 lbs., Venus – 9 lbs, the moon – 1.6 lbs, Mars – 3.7 lbs, Jupiter – 23.6 lbs, Saturn – 10.6 lbs, Uranus – 8.8 lbs, Neptune – 11.2 lbs.
However, the mass of the bowling ball does not change because mass and weight are not necessarily the same. The mass is how much matter the object has, which wouldn't change regardless of the planet.
2. Einstein's Theory of Relativity
Mass has another known definition, namely that it is the amount of energy an object contains. To find the amount of energy an object holds, use Albert Einstein's famous equation: E = mc2. In this equation, E represents energy, m is the mass of the object, and c is the speed of light. Given the same bowling ball from above, the mass of the ball is 7.5kg, and the speed of light squared is 8.98755179 × 1016 m2 / s2. You can then use the formula to find out the energy of the ball, as well as calculate the rate of mass increase as the speed increases.