– Raw product weight vs Earth weight


Lets suppose the Earth weighs 100,000 lbs. (just follow along).

I want to build a car from raw materials. The car will weigh 4000 lbs.

Does the the weight of the Earth change at that point or do the materials of the car equal the final weight of the car?

Same with humans. A baby weighs 10lbs at birth but when grown is 250lbs.

I suppose my question is that is the Earth’s weight a set weight or does is fluxuate barring any meteors an space junk.

In: 1

Earth’s mass indeed changes all the time. On one hand, space debris falls into Earth. On the other hand, light gasses such as hydrogen and helium escape Earth’s gravity. Overall it loses more mass than it gains.

Weight requires a reference point. What you are talking about is mass.

The mass of the earth changes when something is added or removed. If you picked up a rock and threw it to the moon, the mass of the earth would go down and the mass of the moon would go up.

However, building things doesn’t add or remove anything. In your car example, all the metal is mined out of the earth, all the plastic is refined from oil that was in the earth, etc. You’re just repurposing materials.

Now, maybe during refining some stuff burns and loses mass in the process of being made into a new product, but you’re not adding mass when you build anything.

Same goes for babies. We eat food that was already on the planet, no mass is being added or removed, at least not in any significant way. I suppose you could eat some beans and fart and that methane might escape the atmosphere, but I’m getting carried away.

When you dig up a rock, that rock is still on Earth. Whether you want to count it as part of “Earth’s weight” or not is up to you but the total weight of the system does not change.

When a human grows, all of that extra weight comes from plant matter and air and water that was already on Earth. No extra weight.

Thank you. makes sense now.

Always wondered about this.