Time travel ethics / Categorical Imperative

[Horizon]

The time travel rules of Genius: The Transgression are useful in this situation. The first line of that rule subsection:
Time travel is almost always a bad idea.

[Globus]

Personally, in situations where evil is the primary risk, I don't see anything suspect in the judgement of those that make the calculus: probability of evil getting hands on technology X harm potential of technology > good offsets of making technology available.

I do. We have nukes for seventy years now, and we're still here.

[Horizon]

But... but... are you implying that the large governments that possess weapons of mass destruction don't have our best interests at heart?

[Globus]

Giving time travel a little more thought than it is healthy, I came up with this:

If time travel is possible, and doesn't work in a way that makes multiple universes, the probability of the emergence of a timeline where time travel was never invented AND has never accidentally happened approaches 1.[1] If it ever happens, there is no way to reverse it without time travel. This leads to the rather paradoxical statement:

If time travel is possible, then time travel is impossible.

[1]: unless an agent, which is unaffected by time travel, interferes. I'll just Occam that possibility away.

[snowyowl]

That's called Niven's Law of Time Travel. I find it makes rather too many assumptions about the way time travel works, but it probably holds up fine in the BTTF universe.

[Horizon]

Let's all agree that, should someone construct a working time machine, we will all work together to destroy it. And the research notes that don't have other applications.

[Globus]

Let's all agree that, should someone construct a working time machine, we will all work together to destroy it. And the research notes that don't have other applications.

You might want to expel me from your tactical plannings then. See my first post on this page (#12 in this thread). My whole point is that mankind is more resilient than that.

Also, who is this Niven, and how did he manage to steal my idea before I even wrote it?
EDIT: Is he the Ringworld guy? I think he is the Ringworld guy.

[Horizon]

nihil nova sub sol.
Translation: There's nothing new under the sun.

[snowyowl]

how did he manage to steal my idea before I even wrote it?

In a thread about time travel, did you even have to ask?

Of the three main classes of time travel model (as defined here by the Almighty Mason), Niven's Law only holds in the third one.

In immutable timelines the question is irrelevant. The timeline won't converge to anything in particular, because it never changes.

In branching timelines then the question might apply. Branching timelines usually have some concept of "measure": not all histories are created equally. When you reach a branching point, where history could go one of two ways, do you always experience a 50% probability of each one happening, or could there be some distinction between the two? This concept appears, among other places, in quantum physics, where Schrödinger's Cat can be in one of two states but they don't necessarily have equal probabilities of occurring. Anyway, depending on how measure interacts with time travel you might be overwhelmingly likely to find yourself in a universe with very little time travel. Or you might be overwhelmingly likely to be in a universe with lots of time travel. Or both possibilities could be equally likely.

In changeable timelines then un-inventing time travel necessarily causes a paradox, if paradoxes are a thing that can happen. Whoever the last time traveller was, they've just prevented themselves from knowing about time travel at all. If they just fade out, Marty McFly style, expect every trace of their presence to fade out too - including the abolition of time travel. Classic grandfather paradox. If, on the other hand, they survive - sustaining their own existence despite coming from a world that no longer exists - then Niven's law holds and the timeline can stabilise. The operative word being "can". The world will still contain the time traveller himself - someone with knowledge of time travel, who to all intents and purposes materialised out of thin air, who may be carrying future technology on his person possibly even including a working time machine. He can take steps to minimise this - wipe his memories and destroy the time machine. Or use a Terminator-style time machine that won't send back any future technology including itself (note: nudity is not strictly necessary). Or don't travel in person, just strap a grenade to a flux capacitor and send that.

In conclusion: Globus, what makes you think you've given time travel more thought than is healthy?

Secondary conclusion: Free cookies to whoever writes a story about an amnesiac man materialising out of thin air and trying to determine who or what he is.

[Horizon]

In an empty warehouse, a man spontaneously generated, and had no memory. He thought for a moment, trying to figure out who he was, or what he was, before spontaneously decomposing. The end.
Now, where are mah cookies!