I am dubious that gamma ray bursts are invariably a sentence of doom. The actual mechanism is due to the destruction of the ozone layer due to nitrogen molecules formed in the upper atmosphere; these molecules would "eat" the ozone for maybe 4 - 5 years after a GRB event, but would not (in that sort of lifetime) go from one hemisphere to another. Questions I would have include

- How many civilizations might form on bodies with very thick atmospheres, far from their Suns? (Venus does not need a ozone layer to keep the UV out, and might be very habitable a few AU out.)
- How many planets might have very long rotation periods (years), so that the night hemisphere never is subjected to the daytime UV?
- Are there rotation axis directions and orbital precession constants for planets that would keep GRB radiation mostly in one hemisphere, leaving the other to develop?
- How many planets might have other special circumstances that protect their ozone (such as a lack of N2 in their atmosphere, or an ozone generating biology in their stratosphere, etc.)

I am sure that there are others, but even these I think show that, while GRB might be bad for habitability, they need not be fatal. Note, too, that if I was running a Kardashev Type III civilization, one of my action items would be to find any possible GRB progenitors and disarm them. So, in a KIII galaxy, GRB would likely no longer be a problem; maybe that would be a good way to determine the number of KIII galaxies in the universe.

Yes, that is what I meant (and, even, what I said). To get the data you had to join one of the teams and collaborate with the other scientists in the team. Now, apparently, you don't.

I ran some numbers on this, and concluded it would take a good while to cool Venus - you would have to get rid of the clouds somehow to make the cool-down reasonable, and that means an intervention beyond just the shade. There will be plenty of opportunity for note taking and even PhD theses during the process.

There are two proposed solutions to that

- have a swarm instead of a shade - i.e., lots of little shades, which makes the orbital dynamics (and probably the manufacture) of the system much easier to manage.
or
- put the shade not at the Lagrange point, but a little bit sunwards, where the solar gravity, planet gravity and the shade radiation pressure give an orbit period matching that of the planet. There, the shade can be pushed by the Sun's radiation pressure and still be in static equilibrium.

Rosetta getting to P67 was much harder energetically than sending a spacecraft to Venus.

You are certainly correct that any of these would be huge engineering tasks, but they are just engineering tasks. They can be done if there is sufficient will.

The LHC would make an excellent particle beam weapon source, if you should have a starship (generation ship?) big enough to house it.

I was told, at a NSF meeting not many months ago, that CERN never makes its data openly available and never would and that US scientists should just plan on getting European collaborators if they want to work on it.

Now, if we just get ESA to start releasing the Rosetta data...

Well, an Earth sun-shade would need to block at most a few % of the sunshine falling on the Earh, while for Venus (if we want to cool the planet off this millennium) we will need to block all of the Sun's rays for a while, so the engineering is a bit more difficult. Add to this the detail that the Venus Lagrange point 1 is quite a bit further away than the Earth's, and energetically harder to reach, and I think a more reasonable conclusion is that the Earth would be training wheels for Venus, and not vice versa.

I am convinced we will eventually build a sunshade, out at the first (inner) Earth-Sun Lagrange point. It won't help with ocean acidification, but it would make a global thermostat possible.

And, it will be good practice on fixing Venus.

The Wednesday before Thanksgiving is a busy travel day?!? How did that ever escape our attention? I mean, aside from every DJ on every radio station, and every traffic reporter on every TV station, telling us that every year, how could we possibly find such things out if Google didn't do the heavy lifting?

There is a US satellite orbiting the Moon right now, another whose mission just ended, and yet another one 2 years ago.

No, we have not foresworn the Moon.

tt can be baryonic matter, if it is encapsulated in some fashion. I believe your two conditions refer to BBN (not a particularly extreme energy density, BTW) and the Lyman Alpha constraints on Warm Dark Matter (which means it had to drop out of the radiation fluid v ~ c / sqrt(3) pretty early).

Both of these are fulfilled by, e.g., quark nugget dark matter (these would form well before BBN and drop out of the radiation fluid well before needed to fulfill the WDM constraints), as maybe also the recently proposed "macros".

Poisson statistics. I have to wonder if Mr. Haselton has ever heard of the term.

If by some weird alignment of forces I were to become a Judge, and Mr. Haselton presented this to me in a brief, I would try and have him disbarred for abuse of statistical process. I know that the actual legal profession is soft about such abuses, but by God they wouldn't be in my courtroom.

I think it is a safe bet it will be found. They have the photos from the surface, they have the CONSERT triangulation, and of course they have a great desire to find it (and the comet isn't that big). It will be found.

I am going to ignore for now any issues of damage from nearby thruster firings.

Rosetta has 24 bipropellant 10 N thrusters and is 2.8 x 2 m, not counting solar panels. Philae is 1 x 1 x 0.8 m. Suppose Rosetta fires a thruster from 3 meters away - Philae is then 1/3 of a radian across, or about 0.1 steradians. Suppose the thruster has a exit angle of 2 pi steradian (i.e., the whole hemisphere away from the spacecraft, which is surely conservative). So, I would expect Philae to experience a force of 10 N x 0.1 / 2 pi ~ 0.2 N. It has a mass of ~ 100 kg, so that would impart a thrust of 2 x 10^-3 m/sec^2. (I am assuming Rosetta has a thruster firing on the opposite side too, so it's not moving.) That is actually greater than the 67/P gravity, so Philae could move. If this were done for say 10 seconds, Philae would have a velocity of ~ 1 cm/sec afterwards and maybe a total flight time of 30 seconds. Now, it wouldn't move far, but it might get to a little flatter terrain and maybe more sunshine.