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Comment by tsotha | Hacker News Reader

Hawking is wrong. The population isn't "growing exponentially". In fact, it's set to level off mid-century and start decreasing. We're not going to just keep growing like bacteria until we all die.

Having said that, let me say a large extinction event is certainly possible - we may have barely dodged one in the late 1800s:

http://www.theblaze.com/stories/has-the-earth-come-close-to-...

But to plan for something like that we would be better off tunneling into the earth than trying to colonize Mars. The other planets will never be hospitable to human life, and there's no point in bothering with them until we have the technology we need to make the colonies independent. We're a long, long way from that, and sending more rockets to the moon doesn't get us any closer.

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You sure? In the long term, like that an academic like Hawking probably had in mind, population definitely has been increasing exponentially: http://en.wikipedia.org/wiki/Population_growth first chart.

The population is "set to level off"? How are you certain Or not:

http://en.wikipedia.org/wiki/World_population first chart.

Estimates vary. But you can't be any more certain that our numbers will start to decline any moreso than Hawking is that they we'll continue to multiply.

The first derivative is important here. Look at the chart labeled "growth rate of world population".

Better off linking the original article; the site you link takes some liberties: http://www.technologyreview.com/blog/arxiv/27264/

Keep in mind that if any subtype of the population is growing exponentially, then the whole population will also grow exponentially in the asymptote. I'd be hesitant to disagree with Hawking on this.

Not me. I'm always amazed at the things otherwise brilliant people say when they're out of their area of expertise. There was a reason we didn't reach Erlich's 20 billion by the year 2000, even though we could probably grow enough food to support that many.

We're not going to have the technology to make other planets habitable until we have a pressing need to develop it. So no, we shouldn't wait for that.

Well, okay. But by that logic we won't go to other planets unless we have a pressing need, so the whole argument is moot.

Like I said, if your interest is preserving the human race you can can get a lot more bang for your buck by digging into the earth. No matter what's going on at the surface at least you'll have the kind of gravity humans physiology has evolved to expect.

But what about sunshine? Just kidding.

It would be more fruitful to build land on sea first. If the point here is overpopulation.

Sure, if your worry is elbow room. But when people say we don't want to "put all our eggs in one basket" they're typically including things like nuclear war, killer asteroids, and gamma ray bursts.

Yeah, I was referring more to the eggs/basket issue. Beyond that, though, I think there's a lot more to be gained from colonizing worlds than digging into the earth. One is pushing outward, the other is retreating inward, and is very much a dead end.

In fact, it's set to level off mid-century and start decreasing.

Have these kind of predictions ever worked out?

Last time I checked there would always be an unanticipated war or invention to ruin the beautiful projections...

Do elaborate on how war or inventions will make more babies?

It's something I've certainly thought about quite a bit and would love to study more in the future, but the parent post was correct: The population in developed countries will be declining if there are no significant changes in how life longevity or increased birthrates (which can be affected by a lot of factors).

For more information:

Laurence J. Kotlikoff and Scott Burns (2004). The Coming Generational Storm: What You Need to Know about America's Economic Future'. MIT Press. ISBN 0-262-11286. Description and chapter-preview links, p. vii.

The Age Curve: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&#...

Do elaborate on how war or inventions will make more babies?

Well, wars probably remove babies, same for the invention of the anti-baby pill. IIRC neither the wars nor the pill were predicted in the 1900s, just like we can't predict what will happen before the end of this century.

Some big asteroid impact might just end our population concerns for good. Or perhaps we defeat aging with bio-tech. Or designer-babies become so popular that everyone even in developed countries suddenly wants five.

I'm not saying any of that will happen. I'm just wary of predictions reaching more than half a century into the future. After all: We're having this discussion on a medium that nobody 50 years ago would have imagined to exist (outside of SciFi books).

The US "baby boom" following World War II leaps to mind, when we prospered while our economic rivals were recovering from major infrastructure damage. As does the "green revolution" when the world postponed widespread famine through heavy adoption of artificial fertilizers and pesticides and the best known farming tactics.

Well, of course anything is possible. But it's just as likely the population will already be dropping when we expect it to be merely leveling off. One thing is certain, though - the rate of population growth is slowing, and has been for some time.

In terms of a major war or invention, the way I see it these things are more likely to decrease the world population instead of increasing it.

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