Originally posted by FabianFnas
How much does the Earth weigh?
Is this an interesting question?
Is the answer interesting?
Is the answer as obvious as one can imagine?
Was it a trick question? Or was it a straight question?
Normally, for non scientific people, weight and mass is the same thing. Weight watchers, for example, is for reducing weight, but they measure their weight in kilograms. Correct or not? Well, as long we live in a quite homogenous gravitational field it could consider being correct. But not scientifically. (This is the science forum, remember?)
But, however, they correctly use Body Mass Index, BMI, to measure obesity.
sasquatch672 gave an correct answer (I haven't checked) but of a another question. The question should then be "How much mass does the Earth have?"
Palynka gave the correct answer (zero) but as a physics teacher I would only give half a point for it.
The correct answer is - 0 Newton. Full point if you answered this. Weight is measured in Newton, a force. One kilogram at the surface of Earth is equivalent of about 9.8 Newton.
Zero Newton... Why is it so? Well, the planet Earth is in the state of free fall around the Sun. twhitehead gives a more elaborate explanation.
So was it a trick question? Well, the question was crystal clear. And I gave some clues to think it over some.
"Is it an interesting question?" Yes, I think so. Because it make you think of why the question is posed in the first place. Like "Is 2+3 really 5?" It makes you think of what circumstances 2+3 is not 5, and why it is like this. (Perhaps worth a thread of its own.)
"Is the answer interesting?" If the answer is zero Newton, yes. If the answer is som high number metric tonnes, no not particularly. It is too big number to relate to. (My opinion.)
"Is the answer as obvious as one can imagine?" If you give the answer as tonnes, it's not really obvious. If you give the answer in Newton, then it really is obvious. Can the Earth have any other value than zero Newton? If so, how come?
These kind of question are very interesting, in my humble opinion.