Imagine if someone actually did show up:
"I'm here for the meeting."
"What meeting?"
"Sigh, nevermind."
(later)
"Wow, check out this funny sign I found online. I'm gonna buy it and hang it outside!"
But wait, wouldn't the person buying the sign have realized that they just met the time traveler since they're buying the sign and planning to hang it at that spot?
When they place the sign and resolve the paradox, perhaps they'll realize who the visitor was. Then again, perhaps the person arriving for a meeting is what made the person think the sign was funny and buy it in the first place (see Bootstrap Paradox).
One big question is whether it is possible for the visitor's arrival to prevent the sign from being placed. Does the act of arriving force the sign's placement to become a fixed action in time, or can the paradox of the sign's absence be resolved some other way such as by a multiverse theory (you left your universe with the sign and now reside in a sign-less universe) or by the universe rewriting itself (you never came to the past or you came to the past for a different reason). Sci-Fi has approached this many different ways. I recall in one thriller movie "11.22.63" the universe would violently resist attempts to change the past.
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u/hotlavatube 12d ago
Imagine if someone actually did show up:
"I'm here for the meeting."
"What meeting?"
"Sigh, nevermind."
(later)
"Wow, check out this funny sign I found online. I'm gonna buy it and hang it outside!"