Why & how do people measure ‘how big’ a thing is by saying “X is (Y) pounds” are there any mathematical relation to it?
In: Mathematics
The pound is a unit of weight. You can measure it with a scale. One pound is a little bit less than half a kilogram.
People use lots of terms either loosely or just flat-out wrong. When someone’s trying to think of words to describe something really large, “pounds” may just be the first unit of measurement that comes to mind, and they just run with it without really thinking about it.
Big is not a set defined term, it can mean any metric, so when people use it colloquially they sometimes mean mass and sometimes volume.
If they denote a unit of mass then they mean mass.
(Edit: or weight for the pounds, for those who are sensitive to that distinction)
If you’re comparing two things that are generally really similar in structure, weight is a metric you can use that, while being really general, is a bit independent of other factors.
I can say my dog weighs 15 pounds, but that doesn’t really say anything about how tall it is or anything. That may or may not actually be relevant though, if “15 pounds” is good enough. If I compare it to someone’s 3 pound chihuahua, you know it’s bigger and don’t really need to be told it’s longer or taller.
It’s not the most correct way to do it, but it gets the point across.
People measure things by mass, because it’s generally the most convenient.
Every atom of a given element is always the same mass. Therefore, since every molecule of any compound contains the same number of the same types of atoms, every molecule of a certain compound is always the same mass.
Thus, if you know the exact mass of something, you know the exact number of atoms or molecules in it.
Let’s say you run a factory that makes screws. You know how much each screw weighs, so you know how many metal atoms are in each screw.
Therefore, if a customer orders some number of screws, you can calculate their weight, and that tells you how much metal to buy. And if you buy that exact mass of metal, you will always be able to make the same number of screws.
Volume is less convenient. If your metal supplier changes the size of their metal, you can’t order the same number of pieces, but you can order the same mass just fine. And if they change the shape to take up more space, you still need just as many pieces of metal, and it’ll take up more space, but it’ll have the same mass.
There’s no way for a mass measurement to change – if you have less mass, you have less metal, that simple.
And the same goes for other stuff – food, chemicals, objects, whatever.
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