You dont need giant rocks to observe the sun and moon though.

jrootabega 2 days ago | parent | next [-]

What if you want the sun and moon to notice you?

	▲	bazoom42 a day ago \| parent [-]
		At least a much more plausible explanation than the “ancient observatory” theory.

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jvanderbot 2 days ago | parent | prev [-]

You do if you want a durable record of your observations e.g., for the purposes of showing future generations you could align with spring solstice, or predict phases of moon, or eclipses. That's impressive and maybe even useful.