To use a pun, these are ballpark figures to give people a general idea, not an exact measure. Also about as heavy as a midsized car. Just gives people a general idea.
Using “ballpark figure” to explain “football field” is my favorite thing today.
I never quibble with these types of comparisons, except for Libraries of Congress when trying to convey the amount of data something can hold.
I have no idea how large the LoC is. My touchstone for data capacity is MP3s (128k/48kHz, of course :)
As far as football fields goes, I’d think it works best because gridirons and pitches are roughly the same size. Almost everyone has had experience with at least one of those, right?
Well, yes. but in the game the US calls football, (hand egg?) the field is fixed size. What, pretty much, everybody else calls football the field is not fixed size.
90m and 120m are close enough for communicating an approximate impression of size, which is what the football field "unit" is for. People aren't going to recall either of these sizes precisely anyway, nor accurately estimate the size of anything else about this big. Not without training in distance estimation anyway.
i said football field, not pitch. they're measured in yards and all come to 100 of them. glad to know soccer fields vary in length since that means they're obviously not a good unit of measure and there won't be any confusion :)
Akin to stadia.