Earth’s Resources are finite. We may be able to drag stuff down from the space around us but only in very small quantities, the cost per pound of getting stuff from the moon works out to about $250,000 per gram. From low earth orbit it is probably a lot cheaper at maybe $10,000 per gram, so apart from its novelty value to science, it’s probably a poor return. If you regard a fully fuelled Saturn V as around about 2.8 million Kg, and the rocks it returns around 64Kg, then the moon is probably 40,000 times in the red in proportion, low earth around 1600 times, if there was in fact anything up there to grab that was worth it.
So, unless we are living in space or on the moon, the ‘Fred Bloggs, Space Miner’ books are a bit on the fantasy side. If you could mine tritium or Helium 3, then maybe the balance is not so one sided.
That said, the world is running short of resources. I see the current set of fossil fuels, or easy to get at power something like the graph below:
Probably by 2070 there won’t be any simple drillable oil available, gas will have been 50% depleted, and even shale oil will be down to about 83% of all reserves. Shale oil will be around for a very long time, but it’s likely that for each 10% used up, obtaining the next 10% will mean using twice the energy to do it. So the last 10% may take half a million times the energy of the first 10% to release it. Get to this stage and mankind is back to the stone age within decades, possibly for 50,000 years and resources taking this long to recover to usable levels.
This of course may have happened in the past, and we occasionally see remnants and relics just hanging on, hoping for a return to glory.
Light speed, can we bypass it? That is the question. At the moment we need stellar energy level capacity to do things like warps to send single craft out. Play around with antimatter and get it wrong, nobody would know, even at planetary distances, as the planet you did it on may never be detected again, mistaking it for an asteroid field. Without faster than light capacity. entropy means dead craft being aimed at other stars. With accretion we might even mistake them for inter-stellar objects.
I must admit, I am not sold on the idea of purely man made CO2 driving climate change, but I am aware of it having little effect, and the fact that to reduce our CO2 outputs we are using up resources at a faster rate than just producing CO2. The pragmatic view is that this will continue whatever we do, and mankind is still sitting on one target with a big bulls eye painted on it waiting for extinction.