The traditonal first guess in 20 questions is the size question of... "Is it bigger than a bread box?". [I think Dave jokingly raised it in the last go-round.] Boxes that house a loaf of bread are not as common as they used to be, admittedly, but it is a good middle ground question that eliminates a lot of possibilites. An astronomical equivalent is probably a large star, but I already know it is not likely a star, thus the 1 cubic lightyear-sized of "bread box".

Is "20 questions" not a popular UK game during idle time?

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.