Slow takeoff in the sense of Christiano is a far steeper climb up to far higher capabilities than what the "nanotechnology is impossible" folks are expecting. 

Knock off DFW >  knock off 0HP. 

This is helpful. Details about specific traditions and their relative dangers is what I hoped to see. Hard for me to verify, of course, but that's just what it's like when you're out of your depth.

Ooh, good idea. I'll try that out today. 

Reading one of the articles on the site, I get the sense this guy has an axe to grind against Galileo. If I had to guess at my opinion after reading further, it would be that he's using asymmetric standards of evidence for arguments for/against the value of Galileo's work. 

Some random notes on harvesting energy at stellar scales. Again, from Grand Futures.

Harvesting dark energy:
    Tying galaxies together: Anchor big rope to galaxies as they get pulled apart by dark matter. Build up elastic potential energy which can be harvested. Issue: inefficient. You get out < 10^{-39} times energy of rope. Needs negative energy density matter to give better efficiency. Not clear how you anchor rope to energy
    Letting particles expand apart: again, very tiny amounts of energy compared to mass energy of particles. So small it isn't clear if it's even a net return.

Dark matter: 
    Hawking radiation: takes a long time to see any returns. Very poor efficiency for black holes past 10^11 kg. Past that point, it is just neutrinos which are hard to capture. You can chuck in dark matter which isn't very usable and get interacting stuff back out.     

Neutrino capture:
    Lots of neutrinos running around, especially if you use hawking radiation to capture mass energy of black holes. So you might want to make use of them. But neutrinos are very weakly interacting, so you need incredibly dense matter to absorb their energy/convert them to something else. Too dense?

Some methods of extracting energy from ordinary matter using black holes.
  

Accretion discs: chuck in matter to orbit black hole, get very hot and transition into radiation. At most, 5% efficiency for stationary black holes, 43% efficiency for extremely rotating black holes. (With wormholes, you could get 51% efficiency). Very useful for converting matter we can interact with into energy. Not the most efficient but you don't need black holes to have angular momentum to do this, which is perhaps useful.

Penrose process: Extracts energy from angular momentum of black hole, a fair bit of which resides outside the event horizon in the form of frame-dragging spacetime. Have to drop in matter which gains energy, splits into new particles, some of which continue to fall in and others fall out. So not useful for dark-matter, which doesn't transition into ordinary matter. Has 20% efficiency at upper limits for the penrose process, but penrose like processes can get you >10x returns on mass-energy. But you need to use up the angular momentum of the black hole, which is boundedly large for a given mass. But you can get up to 50% for extremal charged black holes, and 29% for extremal rotating black holes. So this is good as long as you've got lots of spinning/charged black holes. Big black holes tend to spin reasonably fast, thankfully.
 

Black Hole Bombs: Another interesting way of extracting energy from black holes are superradiant instabilities, i.e. making the black hole into a bomb. You use light to extract angular momentum from the blackhole, kinda like the penrose process, and get energy out. With a bunch of mirrors, you can keep reflecting the light back in and repeat the process. This can produce huge amounts of energy quickly, on the order of gamma ray bursts for stellar mass black holes. Or if you want it to be quicker, you can get 1% of the black-holes mass energy out in 13 seconds. How to collect this is unclear. 

I always liked this way of looking at the determinant. 

Wholesome. And at this point, I'd be happy if we got a future like this. 

Good catch. I meant when you dump in mass energy into a black hole, it eventually radiates it back out and about half of that radiation is stuff we can make use of: light, electrons, positrons, protons, neutrons etc. The other half is neutrinos.

: ) I'm glad to hear that.