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Comment Re:fire! (Score 1) 54

Are you sure about hydrogen being less leaky that helium? I thought it was the other way around - yes, helium is monatomic, but hydrogen is a lot smaller. The result being, as best I can gather, that an H2 molecule is slightly larger than a helium atom along its long dimension, but notable smaller along its short one.

Then again perhaps I'm thinking of hydrogen under pressure, where it will eventually pass through even solid steel tank walls. I've never heard of helium having such issues, but that could simply be because there are far fewer applications for high-pressure helium storage.

Comment Re:fire! (Score 1) 54

Hmm, on further though, we could fill the aerogel with hydrogen gas - that shouldn't alter the density much compared to being "vacuum filled", and would only a skin that prevented mixing, rather than preventing pressurized leaks. That would essentially eliminate the risks of leaks with even an extremely thin skin, while the aerogel would maintain a rigid airform and essentially eliminate the risk of fires. As of 2013 aerographene had been made with evacuated densities as low as 160g/m^3, compared to 1,225g/m^3 for air at STP, and 89g/m^3 for hydrogen, so you could get 976g/m^3 of lift at sea level. Not quite as good as helium, but you get the rigid airframe for free.

The real question would be how well could it survive pressure changes - a traditional airship has to reduce it's density as it climbs to avoid over-inflating and rupturing - aerogel ships would presumably have to do the same, but depending on gel porosity that could take a lot longer to get the air our (or back in again)

Comment Re:Cool! (Score 4, Interesting) 320

Actually, no, this is a very important result. We've been looking for gravity waves for years, and until now had been unable to detect them despite looking at sources that we should have been able to detect. This detection essentially closes an "uncertainty gap" in the theory - think of it like replacing "Here there be Dragons" on an old map with, "Nothing but open ocean here". It doesn't really change much, unless you happen to want to travel across the previously unknown area.

In addition, the article doesn't mention it, but by comparing the measured spatial distortions with he predicted values we open the door on the study of why the waves aren't as strong as predicted. Is there a flaw in the machine, or some hither-to unpredicted attenuation factor? The latter could potentially be every bit as earth-shattering as when the study of black-boy radiation revealed Quantum Mechanics.

It is in looking for confirmation of the predictions in current theory that both confirm that theory, and occasionally expose its flaws, which lays the groundwork for new theories. It may not be as exciting or glamorous as discovering something unexpected and new, but it's the same exact search that does both, and it's largely the luck of the draw as to whether the previously unexplored nook you chose to investigate reveals anything new. Its primarily through the exhaustive search of such nooks that we discover the unexpected phenomena that allows further theoretical growth. And in that pursuit "nothing unexpected here" is vitally important, as it allows future researchers to concentrate their attention elsewhere. Not to mention, it develops the early stages of the technologies that eventually allow us to harness the phenomena for productive uses.

Comment Re:Cool! (Score 5, Informative) 320

Well, except for the niggling one where it demands a completely different vacuum energy level than the similarly well-tested theories of Quantum Mechanics.

It's an odd situation - we have two well-tested and widely accepted theories, neither of which show any significant cracks, but which are utterly incompatible with each other.

Comment Re:Instance or class? (Score 1) 217

A whole lot of those would seem to fall under the "don't hit things" rules the AI is going to be operating under. You shouldn't have to use any special flagging system, just put out the proper safety cones to block off your work area.

Of course I've seen some really lousy traffic barrier placement too, to the point of following what was to all appearances the proper path, only to find myself clearly on the wrong side of the barriers. That might overtax the AIs "situational awareness", but hopefully it would only take a few accidents before road crews start making sure their barriers are placed unambiguously.

Comment Re:"you don't have to be very accurate" (Score 1) 242

Huh, it appears you may be correct. I didn't realize that the bulk of radioactive fallout material was actually vaporized material from the target that had been neutron-activated. Learn something new every day.

Of course you're still going to have neutron activated nitrogen, oxygen, etc. to deal with, but since they're at high altitude and won't fall out they should be diluted to safe levels before anyone on the ground is exposed, at least so long as we're only talking about a single explosion. There's probably also a lot less air within the neutron decay radius, and once the neutrons decay into hydrogen atoms they're relatively harmless.

Comment Re:fire! (Score 3, Interesting) 54

I would have thought similarly, but Wikipedia says otherwise (https://en.wikipedia.org/wiki/Aerogel). Perhaps a flame-front can't advance fast enough through a rigid structure?

Heat cannot spread through aerogels quickly, nor can the expanding hot air front spread further into the fuel, so I'm guessing only the outermost surface can be thermally catalyzed, and thanks to their incredibly low density there's not going to be a lot of other fuel within range of a burning molecule to absorb the energy before convection carries it away from the surface.

Comment Re:fire! (Score 1) 54

Has anyone actually managed to create a "vacuum-filled" aerogel? My understanding was that they were typically open-celled structures created by replacing the water in a gel with air. Though I suppose if the strength was sufficient you could encase it in an airtight skin and then pump out the air. That might have applications for rigid lighter-than-air craft, or as even more effective insulation. At least until a few days after a pinprick forms somewhere in the skin.

Of course the air can then be replaced by something else quite rapidly, giving them impressive absorption properties. Essentially they're an extremely low-mass sponge.

Comment Re:"you don't have to be very accurate" (Score 1) 242

I'm going with movie-knowledge. A nuke blast is only large compared to conventional weapons. Anything more than a few miles away from the blast will be virtually unscathed, and even much closer to the blast you're mainly talking broken windows and a bit of radiation damage. And hitting a relatively small and valuable target like a city requires precision aiming.

The only really credible threat from a poorly aimed nuke is a high-altitude blast, which would knock out radio communications and spread the fallout over a large area. Messy and expensive, but not really something that lives up to the visceral "Eeek! Nukes!" response.

Comment Re:High altitude nuclear EMP (Score 1) 242

The problem is not North Korea - we could destroy what little threat they pose to anyone other than South Korea today in a matter of days, if that. And doing so would probably

The problem is that China would hardly sit quietly by while we decimate their ally, and *they* are a major threat. For China, the continued existence of North Korea is the best of a lot of bad options. While a land buffer has less military value than it used to, they still don't really want the US to have a stronghold right on their border. Plus they spent a lot of lives defending N.Korea from the US during The War, letting the US win now would dishonor that sacrifice. Neither do they want to lose cheap access to N.Korea's extensive mineral wealth Nor to absorb such a populous and dirt-poor region themselves.

So China is stuck in a similar can-kicking position - they keep propping up N.Korea while hoping that someone more tractable comes into power.

Comment Re:If only... (Score 1) 261

I quite agree that my argument is based on stereotypes. But those stereotypes only have to be valid on average for the argument to be sound.

Would you really care to argue that geeks are, on average, at least as socially skilled as the larger population?

As for women who game the system, I'm not sure exactly what you mean by that, but I imagine even most of them would rather deal with the more socially sophisticated predators - I suspect such sophistication tends to make more profitable marks as well.

Comment Re:So what should we do? (Score 3, Insightful) 560

Ugh, yeah, I hate those sorts of design decisions. I challenge the assertion that it's a brilliant idea though, except perhaps in a "sounds good in advertisements" way - there's a reason buttons tend to show up in groups, because individually they are an *extremely* limited interface.

You can't efficiently choose between more than two states with a single button - cycling is pretty much your only option without a non-trivial tap-code. And that means, on average, cycling through half of the states to get where you want to be. Multiple buttons can be used to reduce the problem by cycling through orthogonal options, or even offering a discrete button for each state.

Personally I prefer multistate switches: Twist the knob (or slide the slider) to the position that reflects your desire and be done with it. One single motion chooses between several options, and once you establish muscle-memory you can achieve precise results as soon as your hand finds a single control, even in complete darkness.

But sadly cost is typically a high design priority, and buttons are usually cheaper to integrate into a device than multistate switches, and the fewer the buttons the cheaper. Which leads to cool-sounding ad copy being used to spin cost-cutting compromises into slick-sounding "features"

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