Fall of civilization / space
I think the fall of western civilization is almost inevitable.
The basic problem is that we have become too comfortable, and too afraid
of loosing our comforts.
This has resulted in a political / legal system where small
groups can prevent changes, even when those changes benefit large groups.
One thing that might help is for there to be a "grand project"
whose importance would be believed to outweigh local disadvantages. The
"Manifest destiny" western expansion of the US met these requirements.
The wars of conquest of Rome, the formation of the British Empire,
did as well. Sadly, so did the Nazi expansion and racial cleansing.
In all of these cases, countries radically expanded their size, and technology and industry.
The american western expansion is probably the best model. While
it resulted in the deaths of on the order of a million natives, that was
in some
sense a side effect. The expansion would have proceeded, and
had all of the societal benefits had the the land initially been empty
of people.
I believe such a "grand project" must meet several requirements:
1. It must be of such fundamental importance, and (possibly more
importantly) be presented in such a way that it captures the imagination
of the
public. It must provide a clear, if long term benefit.
2. It must be solvable with technology, industry, and hard work.
Eliminating world hunger, for example, does not meet these requirements:
If
you produce enough food to feed the world's population, the
population will simply grow. A change in cultures is required - something
that is
socially unacceptable (to modern americans, but not to the ancient
Romans, or imperial British).
3. I should involve a wide range of technologies and human skills.
This will push development on many fronts. A cure for aging, or all disease,
for example, doesn't meet this requirement, because it involves
a fairly limited set of technologies and people.
4. It must be compatible with modern ideologies. World conquest
is presently viewed as unacceptable. Projects that involve massive
environmental destruction (e.g.. large scale climate control)
are viewed as unacceptable.
What does that leave: not much.
Expansion into space remains my favorite - but it will certainly
involve substantial environmental damage, and it has been difficult to
convince
the populace of the advantages.
Developing artificial intelligence is proceeding (in many cases
unintentionally). For this, there is the philosophical question of how
to measure
the benefit of building something that, if successful, is certain
to replace humans.
Finally as for the "sustain our world" issue. Civilizations have
risen and fallen for millennia. I don't think ours is any different, or
that the fall
will be particularly bad. I expect us to follow the model of
Byzantium: hundreds of years of "golden age" (e.g.. slow decline). This
round of
civilization has risen higher than any before. The next will
probably do even better.