Survey says...

[asterroc]

A few questions about terminology in astronomy... For any of the "Something else"s, I encourage you to comment. Or just in general, feel free to comment, though I'd appreciate it if you filled out the survey before you read the comments.

NOTE: third question didn't come out right, it's supposed to read "Are either the words 'size' or 'bigger' ambiguous to you?" If you care to add this in the comments, I'd love to know. :)

[Poll #1929305]

Comments

[sildra.livejournal.com]

Cross sectional area (σ) is often used as the relevant size in physics, because that's the size that determines collision/interaction rates. Sometimes the scattering length (a) is used instead, though. And then there's the complication that usually σ = 4π a², but occasionally it's σ = 8π a² if all the objects interacting are indistinguishable.

[sildra.livejournal.com]

Note that this is particularly useful where an object doesn't have a well-defined radius/volume in the first place (or, at least, what is meant by radius/volume is context dependent), so scattering length can be used as a substitute for radius.