mid-air, air, space, sky, memorization, interval of time
宙 centers on the open expanse above and around us: the sky, mid-air, or outer space. The sense of an interval of time comes from the idea of a stretch or span, and memorization is a rare extended use related to holding something in mental space.
宙 combines 宀 (roof) and 由 (origin, reason). The historical development is uncertain, but the character likely expresses the idea of space under a roof or a defined expanse.
Under a roof 宀, there is a reason 由 to look up: the vast space of the sky and mid-air. Imagine standing in a room and seeing the open sky through a skylight.
For チュウ, picture a huge open space where you can chew gum while floating in mid-air: chew -> チュウ, and the sky is so big you can chew forever.
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universe; cosmos; space
spaceship
space; air; midair
somersault; looping-the-loop
microcosmos; microcosm
hanging in midair; suspended in midair
dangling; hanging; suspended
Einsteinian universe
United States Space Force
National Aeronautics and Space Administration (USA); NASA
inflationary universe
James Webb Space Telescope
Hubble Space Telescope
backflip; backward somersault
big bang theory (cosmology)
Fermi Gamma-ray Space Telescope
primary cosmic rays
generation ship (science fiction); interstellar ark
aerial (acrobatic move); aerial cartwheel; side aerial; no-handed cartwheel
whole universe; total universe; all of creation