The question Reliable length scales in nature has been received very poorly, for reasons I don't really understand. In the help center, it is stated that questions concerning "Experimental designs and results" and "Experimental technology used in physics or astronomy" are on topic. I can reasonably interpret a question about how to make a ruler from objects in nature as falling under both of these headings.
The spirit of the question I asked was about how to make a measurement. I suspect that if I had instead asked how to determine a length scale from, say, observations of astronomical objects, it would have been much better received. (The question of length scales in astronomy is in fact very important for physics--see the cosmic distance ladder.) The differences I can identify between a question about astronomical objects and about terrestrial objects are the following:
- We have sophisticated ways of measuring distances on earth that render length scales of nature unnecessary.
- Plants and animals which provide reliable length scales are also within the purview of biology, and thus are not exclusively of interest to physicists.
- Why would you need to use natural objects for measuring things anyway?
My question to the stackexchange community is: For which of these reasons (or for what other reasons) was the question dismissed?
My responses to the above points are the following:
- Not everyone has access to laser range finders all the time. It is still of interest to be able to measure things in a primitive way. (This is also why "back of the envelope physics" is still an important skill.)
- Science is not mutually exclusive.
- See response 1.
And by the way, there are good answers (in my opinion) to the question in question. E.g. atmospheric pressure and a lake can furnish a length scale: You could fill up an airtight bag and sink it into water until its volume was half what it was at the surface. The depth of the bag is then 33 feet.