Back in May there was a Starship Century Symposium in San Diego. I didn’t attend, but I later watched videos of most of the talks (here, here, book coming here). Many were about attempts by engineers and scientists to sketch out feasible designs for functioning starships. They’ve been at this for many decades, and have made some progress.
(Back when this was new, I added it to my commonplace book. I realized that there's a useful reply.)
One way to judge the status level of an activity is to go to the venue and attend the "reception" or whatever social activities are associated with it. Scan the room and estimate the fraction of the population that is fertile women.
So not gonna happen anytime soon...
"Where exactly would the energy for such an economy come from for a civilization that's not yet interstellar or only barely so? Does the Sun even produce that much energy?"
Some quick Googling reveals human civilization presently consumes about 10^13 watts, and the Sun produces about 4x10^26 watts, 40 trillion times as much. A trillion times current consumption is close enough to that limit that guessing at feasibility devolves into a discussion over the details of Dyson swarm engineering, I think.
I recommended the talks on starships, not the one by Peter Schwartz.
I can't really make sense of this. In the MWI there is no significat information exchange between Everett branches once they have diverged macroscopically, and anyway, quantum mechanics and general relativty don't play well together.
There's no paradox, its all explained how time travel can work in David Deutsch's 'Fabric of Reality', with the Many-Worlds-Interpretation of quantum mechanics. In short, its the same as information exchange between different Everett branches - what comes through the wormholes are the results of different possible outcomes.
I suggest that if you do the math, you will see that (if I recall correctly) all of this is still theoretically possible within one human lifetime (for a passenger only, not an outside observer), to cover 1000 light years or more.
I suppose that if the spaceship has to carry at least enough energy to stop, this probably requires matter-antimatter annihilation.
such as dealing with the intense radiation that you encounter in "empty" space.
Also taking into account blueshift of EM radiation. Go fast enough and even the cosmic background radiation could exert enough pressure to slow you down or just fry you.
As soon as we open the first worm-hole, we should expect SAI (Super-Intelligence) to pop through straight away. So this is an alternative route to Singularity.
Which would be an instance of the grandfather "paradox".
Well, FTL might be possible, but I think it would have to be subject to some pretty serious limitations. For one thing, by the theory of relativity, if FTL is possible, so is backward time-travel, so both are equally puzzling. For another, SAI (Super Intelligence) should have been able to get our region of multiverse by now if FTL/backward time travel were possible. SAI hasn't been able to do it, showing that FTL/time travel is indeed subject to some pretty serious limitations.
The most plausible theory I've heard is FTL/backward time travel is possible, but you need a device at both ends. Essentially, you have to create a pair of worm-holes, and you need a device at both ends.
So for backward time travel, you can't travel back to a time before the first machine is created. And for FTL, someone would have to lug equipment at slower-than-light speed first in order to set up the other worm-hole at the destination you want.
Interesting fact though: As soon as we open the first worm-hole, we should expect SAI (Super-Intelligence) to pop through straight away. So this is an alternative route to Singularity.
Thank you for the comment. Please note that I didn't suggest it would be an easy engineering challenge, nor did I endeavor to apply Newtonian mechanics. I suppose I should have mentioned that I am referring to accelerating at g, as experienced in the (at any snapshot in time) reference frame of the passengers on the moving ship (since that is something that the passengers could be fairly comfortable with, long-term). For the pre-relativistic part of the trip, that also corresponds to approximately g in Earth's frame. Later, it corresponds to a lesser acceleration as viewed in the Earth's frame, so that (of course) the spaceship can never reach c. And yes, you have to spend a great deal of time slowing down too, so that you don't fly past your target. And then to come back, you have to do it all over again. I suggest that if you do the math, you will see that (if I recall correctly) all of this is still theoretically possible within one human lifetime (for a passenger only, not an outside observer), to cover 1000 light years or more. And yes, the engineering is far, far beyond our present abilities, the energy requirements are indeed astoundingly enormous, and there are many great technological challenges involved, such as dealing with the intense radiation that you encounter in "empty" space. So, no one is likely to be doing this any time soon! Best regards.
When the Big Dig plans on a certain contractor being available by a certain date, the effects of an unavailability of that contractor can be ameliorated by finding another contractor.
If wonder if the absence of strict conditionality isn't of the essence. You would naturally look for robustness before you apply best combos.
Just a few years at constant g acceleration yields speeds close enough to c that time-dilation helps considerably.
You can't use Newtonian mechanics at relativistc speeds.
The amount of energy you need to accelerate to a relativistic speed is linear in the time dilatation you get:
To get a 2X time dilatation you need to travel at 0.87c. The energy you require to accelerate a 1000 kg (the mass of a small car) object to that speed is about 9 * 10^19 Joules, about the current electical energy generation of the world in one year.
To get a 10X time dilatation you would need about 8 * 10^20 Joules (the estimated energy of the world total uranium resources).
Moreover, once you get to your target star, you have to pay about the same energy in order to stop.
Events in the near-future require shorter chains. A 2% chance per year of a disruptive black swan yields 90% confidence after 5 years but 13% after a century.
Plans for the near future are also less fragile (i.e. less likely to be strictly conditional). When the Big Dig plans on a certain contractor being available by a certain date, the effects of an unavailability of that contractor can be ameliorated by finding another contractor. If you're designing starships and we discover that dark matter introduces unexpected requirements, all bets are off.
Ultimately, this is based on the exponential behavior of chaining conditional probabilities together; if your scenario requires several uncertain things to happen, the chance that they all happen vanishes very quickly as you chain them together.
Why doesn't this rule out best combo in the situations where it's useful? Don't they typically involve chaining conditional probabilities? For example, construction projects. In another post you say the difference in uncertainty is huge, but that doesn't address that the chaining argument should preclude best combo.
Watched the first video (Starships and Fates of Humankind by Peter Schwartz) and I was negatively impressed:
He talks about faster than light travel, which is already a huge warning sign, and he makes the argument that since we don't know everything in physics, and there might be a paradigm shift, then we might discover a new physics that allows us to invent FTL.
That's wishful thinking at its worst.
Also most of his scenarios for space colonization, even those that don't involve FTL seem unrealistic.
A world dominated by high fertility religious fanatics is unlikely (contrary to his claim, religion is indeed on decline) and if it were to happen, it would be a Malthusian hellhole where people wouldn't be able to afford interstellar travel even if it was in theory technologically possible.
The same argument applies to the "escape from a dying earth" scenario.
The "trillionaires in space" scenario relies on more exotic technology and anyway historically exploration has been always funded by governments.
Ultimately his probabilistic claims are unsubstantiated.
I didn't watch the other videos, but if that was the typical level of the presentations, I suppose we can write that event off as a convention of crackpots.
Yes, but we don't need super-luminal capabilities to visit distant stars within the lifetimes of the travelers themselves. Just a few years at constant g acceleration yields speeds close enough to c that time-dilation helps considerably. You could potentially travel 1000 light-year distances or more. But, if you ever came back, you couldn't tell your friends about the trip (unless they lived to thousands of years old). There's an old song from the movie "Dark Star" that laments a somewhat shorter relativistic journey -- see http://www.youtube.com/watc... and note the line, "I'm young and now you're old."