Honestly, it doesn't sound all that implausible that humans will find ways to expand - if nothing else, without FTL (I infer you don't anticipate FTL)
Obviously I don't anticipate FTL. Do you?
there's pretty much always going to be a lot of unused universe out there for many billions of years to come (until the universe expands enough we can't reach anything, I guess.)
Yes, but exploiting resources in our solar system is already difficult and costly. Currently there is nothing in space worth the cost of going there or bringing it back, maybe in the future it will be different, but I expect progress to be relatively slow.
Interstellar colonization might be forever physically impossible or economically unfeasible. Even if it is feasible I expect it to be very very slow. I think that's the best solution to Fermi's paradox.
Tom Murphy discussed these issue here and here. He focused on proven space technology (rockets) and didn't analyze more speculative stuff like mass drivers, but it seems to me that his whole analysis is reasonable.
Brain emulations sound extremely plausible. In fact, the notion that we will never get them seems ... somewhat artificial in it's constraints. Are you sure you aren't penalizing them merely for sounding "exotic"?
I'm penalizing them because they seem to be far away from what current technology allows (consider the current status of the Blue Brain Project or the Human Brain Project).
It's unclear how many hidden hurdles are there, and how long Moore's law will continue to hold. Even if the emulation of a few human brains becomes possible, it's unclear that the technology would scale to allow a population of billions, or trillions as Hanson predicts. Keep in mind that biological brains are much more energy efficient than modern computers.
Conditionally on radical life extension technology being available, brain emulation is more probable, since it seems to be an obvious avenue to radical life extension. But it's not obvious that it would be cheap and scalable.
I can't really comment on turning Jupiter into processing substrate and living there, but ... could you maybe throw out some numbers regarding the amounts of processing power and population numbers you're imagining? I think I have a higher credence for "extreme singularity scenarios" than you do, so I'd like to know where you're coming from better.
I think the most likely scenario, at least for a few centuries, is that human will still be essentially biological and will only inhabit the Earth (except possibly for a few Earth-dependent outposts in the solar system). Realistic population sizes will be between 2 and 10 billions.
Total processing power is more difficult to estimate: it depends on how long Moore's law (and related trends such as Koomey's law) will continue to hold. Since there seem to be physical limits that would be hit in 30-40 years of continued exponential growth, I would estimate that 20 years is a realistic time frame. Then there is the question of how much energy and other resources people will invest into computation.
I'd say that a growth of total computing power to between 10,000x and 10,000,000x of the current one in 20-30 years, followed by stagnation or perhaps a slow growth, seems reasonable. Novel hardware technologies might change that, but as usual probabilities on speculative future tech should be discounted.
I'd say that a growth of total computing power to between 10,000x and 10,000,000x of the current one in 20-30 years, followed by stagnation or perhaps a slow growth, seems reasonable
From Wikipedia:
...Although this trend has continued for more than half a century, Moore's law should be considered an observation or conjecture and not a physical or natural law. Sources in 2005 expected it to continue until at least 2015 or 2020.[note 1][11] However, the 2010 update to the International Technology Roadmap for Semiconductors predicts that growth will slow at
Background:
On the most recent LessWrong readership survey, I assigned a probability of 0.30 on the cryonics question. I had previously been persuaded to sign up for cryonics by reading the sequences, but this thread and particularly this comment lowered my estimate of the chances of cryonics working considerably. Also relevant from the same thread was ciphergoth's comment:
Based on this, I think there's a substantial chance that there's information out there that would convince me that the folks who dismiss cryonics as pseudoscience are essentially correct, that the right answer to the survey question was epsilon. I've seen what seem like convincing objections to cryonics, and it seems possible that an expanded version of those arguments, with full references and replies to pro-cryonics arguments, would convince me. Or someone could just go to the trouble of showing that a large majority of cryobiologists really do think cryopreserved people are information-theoretically dead.
However, it's not clear to me how well worth my time it is to seek out such information. It seems coming up with decisive information would be hard, especially since e.g. ciphergoth has put a lot of energy into trying to figure out what the experts think about cryonics and come away without a clear answer. And part of the reason I signed up for cryonics in the first place is because it doesn't cost me much: the largest component is the life insurance for funding, only $50 / month.
So I've decided to put a bounty on being persuaded to cancel my cryonics subscription. If no one succeeds in convincing me, it costs me nothing, and if someone does succeed in convincing me the cost is less than the cost of being signed up for cryonics for a year. And yes, I'm aware that providing one-sided financial incentives like this requires me to take the fact that I've done this into account when evaluating anti-cryonics arguments, and apply extra scrutiny to them.
Note that there are several issues that ultimately go in to whether you should sign up for cryonics (the neuroscience / evaluation of current technology, estimate of the probability of a "good" future, various philosophical issues), I anticipate the greatest chance of being persuaded from scientific arguments. In particular, I find questions about personal identity and consciousness of uploads made from preserved brains confusing, but think there are very few people in the world, if any, who are likely to have much chance of getting me un-confused about those issues. The offer is blind to the exact nature of the arguments given, but I mostly foresee being persuaded by the neuroscience arguments.
And of course, I'm happy to listen to people tell me why the anti-cryonics arguments are wrong and I should stay signed up for cryonics. There's just no prize for doing so.