[dstorrs]

Why?

Or, perhapse "Why is that obvious / why is it a necessity?"

If humanity expands into space, there is absolutely no reason for the population to ever stop growing. Space contains more energy, more living space, and more resources than we could possibly use.(1)

In fact, give the release of resource constraints, there are good arguments to keep growing--"given enough eyes, all bugs are shallow" applies to more than just software. More people is a good thing.

(1) For a really good treatment on this, read Professor John S. Lewis's _Mining the Sky_ http://www.amazon.com/Mining-Sky-Untold-Asteroids-Planets/dp...

[abefortas]

I would have responded earlier if I had noticed this.

You're right that it's not quite a necessity. It's concievable that population growth could continue, albeit at a very slow rate, until people are ready to colonize space. I don't doubt that humans will figure out how to do that-- if they survive long enough.

But it seems likely to me, maybe even obvious, that at the current rate of growth people are going to commit evolutionary suicide long before that becomes possible. This because the earth is very limited and recently economic growth has been really fast. In addition to the Club of Rome stuff recommended above, check out: Capitalism Nature Socialism, a pretty good journal which often discusses these issues, and Beyond Growth by Herman Daly.

Edit: note that it was I who upvoted your comment.

[dstorrs]

Thanks for the upvote. I had actually wondered--is there any way to know who has up- / down-voted a comment?

As to the growth issue, I'm not quite sure what you mean by "evolutionary suicide." My first guess would be that this term applies to a species that fails to adapt to a changing environment or, in the case of a sentient species, chooses to consciously direct its evolution in a direction that renders it unfit for its environment. That doesn't seem like a good fit for your argument though, so I think what you likely meant was that the population will outgrow the available resources, and there will not be enough food / energy / medicine / etc for everyone. If I'm wrong, please correct me.

Assuming that this is what you meant, I see several implicit assumptions that are worth examining. They are:

1) Humanity does not currently know how to colonize space.

2) It will be S years before we colonize spaces, and S is a large number ("a long time"). This probably means decades, possibly centuries, although you don't specify.

3) The current rate of worldwide population growth will be sustained into the indefinite future.

4) The resources of the Earth are too limited to support the world population that is projected to exist in X years, where X is a small number of decades.

5) X years < S years.

6) Our current knowledge of the Earth's resources is complete and correct.

If any of these points prove incorrect, I would be hard pressed to agree with your argument.

Considering some of the news reports I have seen in the last year or two, I suspect that there might be more resources out there than we think, and that space colonization might be closer than we think:

- Yesterday's NY Times carried a major article about a new technique for natural gas recovery from shale.

- I am aware of at least one study that shows a space elevator could be built for about the price of Boston's Big Dig (i.e. ~10-20B). With such a construct in place, the two major hurdles in space development (launch costs and risk of catastrophic launch failure) go out the window. Even if that study was low by an order of magnitude, it's still something that any G8 government could afford, as could a conglomeration of major corporations.

- JAXA (the Japanese NASA) is currently working on a solar power station project. If powersats prove out, they will represent a major incentive to start building up space infrastructure, which will naturally lead to more people staying in space longer, which will naturally lead to colonization.

- It is pretty clear that population growth tends to level off and even decline once a nation reaches a certain standard of living and life expectancy. Europe and Japan are good examples of this: negative population growth and/or aging populations. More people aren't the problem, they are the solution: we need more minds coming up with ideas, and more hands producing wealth world-wide.

[abefortas]

You're right. That's what I meant by evolutionary suicide, and my argument (well, it's not really mine) relies on all six assumptions, more or less.

Although:

Colonizing space and colonizing space to the point where you don't need to worry about earth's carrying capacity are two quite different things. Energy and minerals might be obtainable from space somewhat soon. But we can't eat rocks or sunlight.

I don't claim population growth will be sustained into the indefinite future. I claim that it will be sustained until it stops, and that how it will stop is a question of serious concern.

As I see it there are several possibilities: 1.Population growth continues apace and, due to reproductive time lag, there are suddenly far too many people on the earth. This has a quite catastrophic domino effect and an appalling number of people, maybe 100%, die. 2.Population slows and then stops, but people's lifestyles get more and more decadent and far too many resources are transformed into far too much waste. Something, or many things, run out and disaster ensues. 3.Both population growth and resource consumption naturally find some sustainable level. Maybe that would be somewhere below where it is now. Maybe someone would invent something fabulous, say a glass elevator like in Charlie and the Great Glass elevator, and there is room for lots more consumption and lots more people.

Obviously, I prefer the third option. Maybe it will be that. I'm just sufficiently unsure to be worried about it.