Archamasse t1_iu4pq3y wrote on October 28, 2022 at 3:12 PM

Reply to comment by meowskywalker in Movies or TV that says you can beat fate by Beau_bell

Grandfather Paradox is the opposite to a Bootstrap Loop, and it predates Futurama - the premise is that you have travelled back to kill your grandfather, not be him, thereby preventing yourself being born, which means you couldn't have gone back to kill him.

T2's Grandfather Paradox is that by preventing the war, they're preventing Kyle being born (and incidentally, John) and the time travel tech he used existing, which should mean it's impossible to prevent the war.

Futurama inverted it as a meta joke.

meowskywalker t1_iu4s6qp wrote on October 28, 2022 at 3:28 PM

Weird. I always heard it used to describe how Skynet can’t exist unless it’s sends terminator back to be used as the building blocks for Skynet, long before Futurama. Why do we need that term when paradox already describes it? I understand why we need bootstrap or predestination because it describes a scenario where we sidestep that issue even while the paradox already exists.

Archamasse t1_iu4vrk0 wrote on October 28, 2022 at 3:52 PM

There are other theoretical types of paradox in conversations about time travel, though most are about how "real" time travel would affect the world.

For example, the Fermi Paradox - "where is everyone?". The idea is that, if time travel will ever be possible, travellers should already have started coming back way in the past already and any character or person learning about it for the first time should probably take it for granted.

Another, arguably a Grandfather Paradox variation, is the Hitler Paradox. Say for example I headed back in time to prevent something happening, did it successfully, and headed home. This is a paradox, because now there's no way I could have known about the event I just prevented in order to prevent it. There was no reason for the time travel to happen at all and the future I go back to shouldn't be the same as the one that sent me. So how did they send me, and will there be another me when I get back?

The Grandfather Paradox is specifically about the traveller's own existence. They have prevented themselves existing to prevent their own existence.

Skynet's situation is sort of another Bootstrap Loop, it seeds itself in the past just as John ensures his own conception, by steering Kyle towards it.

meowskywalker t1_iu4wfhc wrote on October 28, 2022 at 3:57 PM

See I guess I have the same issue of why do we need a different term for “Hitler” and “grandfather” paradox. They both describe the same logical problem. You can’t go in to the past to change the past because by changing the past you create a present where you wouldn’t be able to go back and change the past. Whether it’s because you were never born or because you’ve never heard of Hitler seems to be splitting hairs.