Tuesday, 31 March 2009

Shooting The Messenger

It would appear from this week's Lost that the show is about to offer its answer to the Grandfather Paradox. If Sayid's relationship with Ben resulted in Sayid being sent back in time, but then he shoots Ben dead whilst the latter is still a boy, what happens?

From what we've already seen it appears the answer is that present-day Ben falls into a coma, which makes precisely zero sense, but then this is time-travel and none of it makes any sense anyway. (Update: plus, Gooder reminds me in comments that it was a bad case of being hit with an oar that felled Ben, though of course there may be more going on there).

It did though remind me of a conversation I once had with a former girlfriend. Her theory, assuming time travel is possible, is that the Grandfather Paradox was actually irrelevant, because it would be impossible to cause sufficient change to the universe to obliterate oneself. Since you already exist, you can't have succeeded in destroying yourself. Something must have happened to prevent it. (Update: the ever-knowledgeable Pause tells me in comments that this is known as the Novikov Self-Consistency Principle; I can't remember if Rockgirl told me that at the time or not).

Because I'm a mathematician and I love having arguments, I started trying to work out the specifics of her theory. I asked whether it would be possible to find a time machine at location A at time B to go back in time, and send a letter to yourself telling you not go to location A at time B. Or, more plausibly, ask them to go to location C at time B instead. Possibly, in my case, by suggesting location C is a strip-bar with a sale on.

Her response was that the letter would be intercepted. I asked what would happen if I sent two letters, the first one and a second one, that either did suggest location A at time B, or was just totally irrelevant to anything. How would this "interception" work? How would it know which letter to block? It would be like playing Russian roulette with the laws of causality.

This was the point at which she got annoyed. Or at least, the point at which I noticed she was annoyed, which experience has taught me isn't often the same thing.

Once you get to this point, though, you're stuffed. You can't make any action that will potentially prevent you from going back in time, no matter how oblique the connection is. Absent the concept of God, then you also can't make any action that under other circumstances would potentially prevent you from going back in time. That means that either a) the universe is conscious in some sense, and prevents too much interference, or b) the universe would block any attempt at time travel whatsoever.

The latter option, of course, seems more likely. There's the other theory that each trip through time would create its own reality, which of course solves some questions and raises others, but I'm sticking with b) for now.

Anyway, that concludes this somewhat rambling post. Any other time-travel theories people want to share? Logical corollaries to my witterings? The phone lines are open...

13 comments:

Pause said...

That would be the Novikov self-consistency principle, as it's sometimes known, then. At some level (admittedly a largely philosophical one) I wouldn't have thought this incompatible a deterministic (quantum-ness aside) universe; one line of argument would suggest that from the past's point of view this event has already happened (or not), and so what happens in the future must already be laid out; any attempts to interfere by using a time machine are (knowingly or otherwise) simply acting according to the 'grand plan' all along. By such reasoning, the universe is not 'stepping in' to stop the event, because it was already prescribed that it wouldn't/hasn't happened. Such a person would argue that there's nothing to 'stop'; either it already went ahead or it didn't, and you're merely filling in your end of the bargain in the future.

(This is not an endorsement of the idea on my part, I add, nor a suggestion that it should be by you either.)

Alternatively, if you appeal to quantum reasoning to provide some flexibility to a deterministic sequence of events, you could suggest that your actions with the time machine create a new parallel (perpendicular would be more accurate) universe at the moment of observation/interference in the past; thus both events (or the event and the non-event) occur in separate timelines.

SpaceSquid said...

"By such reasoning, the universe is not 'stepping in' to stop the event, because it was already prescribed that it wouldn't/hasn't happened. Such a person would argue that there's nothing to 'stop'; either it already went ahead or it didn't, and you're merely filling in your end of the bargain in the future."

Indeed. Of course, this simply means that the point of intervention happens earlier, because you still need such a thing to ensure that the universe doesn't end up with a causal loop later on.

The quantum reasoning angle is a lot less problematic logically, though I'm completely unqualified to speak on the subject beyond that.

Gooder said...

Er, is it worth noting the Ben is unconcious in the present becasue he was wacked round the head with an oar, not because he was shot in the past.

Gooder said...

Er, is it worth noting the Ben is unconcious in the present becasue he was wacked round the head with an oar, not because he was shot in the past.

Gooder said...

Also worth noting, i've managed to post twice!

SpaceSquid said...

Apparently so worth it you mentioned it twice.

Still, when you're right, you're right. I'd managed to forget that.

Well, in that case I'm going with Ben was wearing a bullet proof vest. Did they even have those in the Seventies?

jamie said...

I'm impressed you managed to forget that he got whacked round the head with an oar this week (which I had remembered), and you remembered that Locke found him unconscious two weeks ago (which I had completely blanked).

SpaceSquid said...

I think at present nothing's really going in but thesis corrections. Plus cider, obviously.

Senior Spielbergo said...

Hmmmm... Interesting. I shall give this some thought but I will just say that I have had a similar conversation with one of your ex-girlfriends, so I'm now curious if it is the same one...

SpaceSquid said...

It will be. You've only met two, and the other one is unlikely in the extreme to have a conversation within thirty miles of something as tawdry as "science".

Senior Spielbergo said...

Well now I'm just going to have to engage my brain to figure out who the second one I've met is...

SpaceSquid said...

Shouldn't be too hard; you slept with her.

Senior Spielbergo said...

You seriously expect me to remember such details as names?