Stephen Baxter, Manifold Time, Doomsday, and spoilers

[Almo]

I just finished Manifold Time. Which is a very interesting book. What bugged me was the Carter Catastrophe.

The probabilistic doomsday prediction, called here the "Carter Catastrophe" is real. It has been well expressed by John Leslie in The End of the World.

When I read it coming from the character in the book, it really sounded like the author believed it. I'm hoping he doesn't mean the prediction is sound, I hope he just means it's a real prediction. I also worried when the best argument against this sillyness was presented in a chain email in the book, which seemed to make it sound desperate. But it sounded correct to me.

Its argument is in essence that if humanity survives, we are in the very early 0.001% of humans that will exist (or smaller). That's unlikely, so we must be near the end of humanity. Statistically a doomsday must be around the corner.

In my opinion, that is patently moronic. SOMEbody has to be in that early percent if we survive. You can't use a probabilistic argument like that on an event that already happened. We are in fact here. Discussing how likely that was now makes no sense.

Maybe he just needed to make it sound good so the characters who believed it didn't seem daft for doing so. Still, I wouldn't have said in the back that "it is real" without making it clear whether I thought it made sense or not.

[lionking]

So how did the first humans survive, as they would have been a minute percentage of all humankind to follow? Or am I not understanding the argument?

[shadron]

Far more than you ever wished to know about it, including about a dozen counter-arguments: Doomsday argument. It is named for an astrophysicist, Brandon Carter, who voiced it in 1983.

[Almo]

So how did the first humans survive, as they would have been a minute percentage of all humankind to follow? Or am I not understanding the argument?

You're following the argument fine, I think. :confused:

[JohnG]

I remember being a little troubled by it, too when I first read about it. Is it possible that it's one of those things like the Fermi Paradox that sounds convincing at first blush, but falls apart once you analyze it carefully?

I've only read the first Manifold book, but my favorite of his novels is The Time Ships, which is a sequel to Wells' The Time Machine. I recommend it to any fans of the original book or time travel stories in general.

[JohnG]

Dupe post

[Almo]

I remember being a little troubled by it, too when I first read about it. Is it possible that it's one of those things like the Fermi Paradox that sounds convincing at first blush, but falls apart once you analyze it carefully?

Yup, though I found the Fermi one more convincing. The description in the book compared it to:


I have a box. It has 1000 balls, or 10 balls in it. One is white, the others black. There's a lever that gives one ball at a time. You push it several times. On the third time, you get white. How many balls are in the box?

There's a damned good chance it's 10, since it's so unlikely to get the white one on the third pull if there are 1000 in there. So, if there are going to be 100 billion quadrillion humans, what are the chances you're one of the ones in the first billion? Slim. So there will most likely not be 100 billion quadrillion humans. So we're doomed, and soon.

The two problems are different. You were told beforehand there were either 10 or 1000 balls, and that there will be only one white one. With humans, we have no idea how many there will be, and there are no milestone people like the white balls, so you can't make a judgement.

One character in the book ate it up, the other didn't (though the world at large went for it). I'm still not sure whether the author wanted the reader to eat it up as well or not. Maybe that wasn't important to the author.

[Wudang]

Yes, once something has happened the odds of it having happened are 100%. It's also against the principle of mediocrity.

[sphenisc]

So how did the first humans survive, as they would have been a minute percentage of all humankind to follow? Or am I not understanding the argument?

The argument is based on probability - by specifically selecting the first humans you've chosen to look at the group where, had they applied the reason, they would have produced a 95% confidence interval which history has shown would not contain the end of humanity.
But you've deliberately chosen that group in order to produce that end result, if you'd chosen more randomly from past and future humans then the interval is more likely to indicate that humans would currently be alive.

It's rather like (loosely) rolling a die a 1000 times to see if it's fair and then pointing at a sequence of 4 sixes and saying "If we'd only seen that we'd have never thought the die was fair!"