Blinkmoth Urn has an ability that only works if it is untapped at the start of a player's main phase. It has no activated abilities.
Can I, on my turn or any other turn, tap the artifact just to tap it, so it won't become untapped until just before my main phase? Is it legal to tap a permanent even if you are not paying a cost nor resolving a tap effect?
(If possible, a citation from the rules would be helpful, as the answer affects a coworker's main Commander deck.)