[nefitty]

The hard variable is paradigm-shifts. We see things like quantum computers now, which seem boring at the moment, but the sorts of problems they'll be able to handle are staggering to imagine.

Robotics keeps improving, eg replacement/enhancement of human labor. That's a paradigm shift.

I definitely see your point about physical limits. I propose that we're nowhere near our ideational limits, which give us the imaginative capacity to form new solutions within those limits you cite.

[baq]

> I propose that we're nowhere near our ideational limits, which give us the imaginative capacity to form new solutions within those limits you cite.

the problem is, thermodynamics is so generic that it's hard to imagine how to sidestep it - and people do try all the time.

e.g. imagine we have a commercially viable fusion reactor, which translates to basically unlimited energy once you build enough of them that they can be operated and maintained using only fusion power from sister reactors. sounds like post-scarcity world, except if you keep power consumption growing for like 1-2% a year, you'll boil the oceans in a few centuries due to waste heat.

if you invent a technology to capture and repurpose enough waste heat to avoid this problem, you sidestep thermodynamics. if you sidestep thermodynamics, there's a lot more you can do than just making fusion 100% efficient...

[jstanley]

There are several potential paradigm shifts which this doesn't address.

For example, power consumption may stop growing even while "real" consumption continues to grow. Or we may spread to other planets so that power consumption can keep growing and we don't care if the oceans boil.

Or something else might happen that is hard to predict in the same way that medieval people would find the Internet hard to predict. Medieval people may have made equally valid claims about bounds on the speed at which a messenger can transmit a message, even if you manage to develop a commercially viable racehorse that can run at top speed 24/7.

[Retric]

Medieval people where aware that you could send messages faster than a horse.

Flag signaling between boats is very old and eventually turned into a messaging system that could go 191 km in 5 minutes. Smoke signals where perhaps the oldest form of long distance communication, and was used across the full 7,300 kilometres Great Wall of China. Though actual speeds are less clear.

For physical messages, attaching them to projectiles or birds was also used. A man on foot or a horse had other advantages.

[cryptonector]

> the problem is, thermodynamics is so generic that it's hard to imagine how to sidestep it - and people do try all the time.

Population is already set to decrease.

Speaking of thermodynamics...

The life-carbon cycle on the planet is not a reversible process. Photosynthetic life, and sea life (sea shells require a lot of carbon) pull down a lot of CO2 from the atmosphere. Sea life in particular leads to carbon being sequestered in limestone over millions of years. Land life leads to carbon being buried in soil. This process trades low-entropy, high-energy sunlight for high-entropy, low-energy light emitted back to space by the planet (keeping us in equilibrium), with the entropy going into things on Earth, like the conversion of CO2 into limestone.

The biggest and shortest-term natural threat to life on this planet is dwindling atmospheric CO2. At the end of each glacial period (thus the beginning of each interglacial) CO2 is lower than at the end of the previous glacial period, and it has been thus since the beginning of the current ice age, and it seems like a pattern that will keep repeating. Eventually the Earth will fall below the photosynthesis starvation level of atmospheric CO2. Before the Industrial Revolution, and the oil&gas revolution in particular, that was going to be just a few more glacial periods. By raising atmospheric CO2 to 400+ppm we've bought the planet a few million years, and even so, if humans were to disappear in the next glacial period, we'd be looking at a closer end to life on the planet through exhaustion of atmospheric CO2 than through astronomic catastrophes like a large asteroid hitting the planet.