OK, I've looked it up [warning: large pdf], which I don't think you have. Show me the evidence that the much worse Chernobyl accident caused, or is yet to cause, more than a few hundred deaths.

The reaction then stops being self sustaining, and you just have to recover the containment units and repair the reactor.

At Fukushima, the reaction stopped being self sustaining seconds after the quake, and minutes before the tsunami. It didn't save them. You can't just wash your hands and say 'problem solved' when the chain reaction ceases. Fission products will keep generating large amounts of heat for months afterwards. If your 2-3 smaller tanks have no way to lose this heat, they will eventually melt.

I'm not saying that these new reactor designs can't deal with this, but you need much more evidence before can claim it's "literally idiot proof".

I was wondering the same.

Detecting gamma rays is pretty easy. Detecting within a few degrees which direction they came from is much harder. Lenses and mirrors won't work (at least, at any reasonable scale) to form an image. You could have two layers of detector, and measure the location of the gamma ray as it passes through both. You could look for Compton scattered electrons from the gamma ray, which would be easier to determine the direction of, but I don't think that would fit in something camera sized.

I'm also curious to know what exposure time the gamma ray camera needs - I'm guessing it will be pretty long - minutes, at least, maybe hours.

The probability is exponential in n, but for two planets, it is polynomial in p. I'd fixated on the second fact and missed the first. Given the context that we'd just changed n rather than p, I agree that 'exponentially' is more appropriate here.

I shall submit myself to the Committee for disciplinary action.

Early supernovae wouldn't help - the star is formed from the same material as the planets would, and the star demonstrably has almost no metals. Early supernovae would just mean that this star didn't exist (in its current chemistry), or that it is even younger than currently estimated, so as to form before the supernovae.

Interstellar captures are very difficult. Generally speaking, you need three gravitationally interacting bodies to allow a capture, as you need one to carry away some energy. Basically this requires the wanderer planet to turn up just when the star is passing close to another one, and even then to get really lucky. (Most often it is the lowest mass object of the three which gains energy, but we need the planet to lose energy.) Another possibility is you could lose that energy through tidal losses, but this requires the wanderer has very small positive energy initially, and passes very close to the star. Either way, the odds of such a capture are very low.

In addition, we have the fact that this star has two planets, which makes the odds against capture polynomially* smaller. Finally, if two planets were captured, we'd expect them to have different orbital planes. Given that they were detected by the 'wobble' method, I'd expect this could be measured, and would be mentioned if it had been so. However I can't promise that there aren't gravitational interactions which would bring the orbital planes into alignment over 13Gyr. Captures would also initially have highly elliptical orbits, which again the wobble method should notice, and again I don't know if 13Gyr is long enough to circularize the orbits by tidal effects or planet-planet interactions.

* This word brought to you by the Committee Against The Misuse Of The Word 'Exponentially'

If ITV Digital was a publicly traded company
And it has ceased to exist due to bankruptcy
And the bankruptcy proceedings have been all wound up
And the allegations against BSkyB are true
And BSkyB can be successfully sued for large damages for what they did to ITV Digital

Who could bring such a suit? How would the proceeds be distributed? The obvious candidates are ITV Digital's creditors (who got paid less than they were owed) and ITV Digital's shareholders. However, it won't always be clear who owns those shares and bad debts, as they've been assumed to have zero value, so haven't been tracked since the end of bankruptcy.

I was thinking this. However, now you require two planetary bodies to occupy the same orbital zone for long enough for them to form without colliding, and yet to collide later on. This is tricky, but perhaps not impossible. They might initially form in some orbital resonance (probably one of the Trojan points) and then some other body comes by and destabilizes the orbits. (I don't know if Trojan points are stable in a still-accreting-planets disk.)

Another possibility is there were two collisions: Theia itself was formed from proto-Earth in a collision, and then later caused the moon-formation event.

Yes, but 80% of the cost will go to the senior managers who are paid $1M/hour.

I'm anti-libertarian and I think it was reasonable to call this a troll. It was fine up to the sentence starting "I suppose..."

The stuff with a half life of 24,000 years is only very mildly radioactive. That is pretty much what "long half life" means. I'd be surprised if that plutonium wasn't more of a chemical hazard than a radioactivity hazard. GP says "the bulk of the radioactivity..." You can't invalidate that statement with examples of minor sources of radioactivity.

Fukushima had a total coolant failure, and didn't go critical, but it was certainly dangerous. And there they had (and used) the option to pump cold water into the primary coolant loop and vent steam from it - an option which wouldn't be available with sodium.

Reprocessing fuel is in itself dangerous: the third worst nuclear accident was at a reprocessing plant. I suspect your analysis of waste reduction through reprocessing is highly optimistic, but I lack the expertise to say for sure.

That would be from anywhere on Earth with a high intensity particle accelerator to anywhere on Earth with a huge particle detector buried hundreds of metres underground.

IPOs and share issues help the economy, but nobody would buy these shares if there wasn't a way to recover the investment (hopefully with a profit) later. The only shares I own were purchased directly from the issuing company. (Which reminds me - it is over a year since I looked at their value. Crud - they're both doing horribly.)

The share market also provides a mechanism for takeovers and mergers.

Investing in shares for time spans of months is of general benefit to the economy, directing investment dollars to those best able to use them. Millisecond trading is of no benefit to anyone except millisecond traders, and any money they make is at the expense of people trying to do something productive. I propose that stock markets shift to a 'clock pulse' trading model: Trade bids for (e.g.) Apple are accumulated for (e.g.) 5 seconds and then all sales are resolved without regard for the order in which the bids arrived. This will cause no problems to real investors, but will rid us of the millisecond leaches.

However, I am not experienced with the share market, so constructive criticism is welcome.