[gazrogers]

If people's lifespan was no longer determined by their body succumbing to the ageing process, they would still be able to die by other means. The population would explode (even more than it currently is) because far fewer people were dying and most people were still having sex and creating more immortals. At some future point (probably not too far away) there would not be enough food on the planet to sustain the lives of all the people living on it. This would lead to mass starvation and/or world wars over land to grow food.

Unless our research into creating immortals also throws up a way for us to photosynthesize, it's really not worth it. Far better, I think, to accept that our time on this earth is limited, and to make the most of what time we have. :-)

[sergiosgc]

Tackle one problem at a time. For one, we may be able to photosynthetise, we just need to create tools for that, and that's what humanity is good at. If not, there are other venues for dealing with overpopulation: population control, out of planet migration... Sci Fi novels have approached this problem for ages.

[gazrogers]

Even assuming infinite ingenuity in humankind, our lifespan will still be limited by the lifespan of the universe. The second law of thermodynamics is not going to be broken no matter how clever we are. :-)

[nnq]

...not resisting the temptation (deleted my other com because it pushed things in a whole wrong direction...): second law of thermodynamics applies to a finite closed system. We know incredibly little about the universe, it may very well be infinite (not just as "time and space" but also as matter and also as complexity of matter - yep I even accept the fact that there may be no fundamental particles, just infinite complexity somehow "simulating" order at our level, and this leads to the fact that we don't really know how little energy do you need to sustain human-type intelligence and it may be very, very little actually) and the "universe" may very well contain "gateways" that inject or subtract energy from our own to other infinite or finite universes - our primitive astronomy neither proves nor disproves anything. Oh, then there's the complicated problem with mathematics and logic - you can't really use the latter as a sound base to explain all of the former according to some so you might have all sorts of interesting consequences like "infinity of logic" or "mathematics" itself - the kind of problems that you can't even dream to tackle when limited to a human lifespan and a human body or brain... The fact is we are incredibly small and stupid at the scale of the universe! The point in living more is the pleasure of discovering more, always more - the pure and beautiful greed and hunger for more and more life, knowledge and power, the hunger that fuels everything.

And the second law of thermodynamics itself... well, we don't have "general" definitions for neither lifer nor consciousness so the truth is we have no freaking idea how something like the second law connects to anything about us. Then again the universe is so big that by the time we think our offspring will have to ask themselves these question in order to survive, they will probably even laugh at our primitive minds and the stupid questions they asked.

EDIT: some intellectual hard drugs for those that find it hard to "believe in the future": http://thisisjasonsilva.com/ - nobody expresses my view better than this kid.

[sergiosgc]

But then the timescale and physical extent of the universe are conditions of such magnitude that tackling the problem is the poster child of premature optimization.