So don't they have iPhones, or Blackberries, or Nokias, or any of the thousands of phones not made in Korea (most made in China) there? Or is this about some sort of import duty?

Interesting. Honestly curious Brit here - I know that US employees suffer lower levels of personal income tax than in the UK (or Europe) but I'm wondering if your employers pay more?

So, $19.2 million, divided by 8 years, divided by 34 people equals...
The toll-collectors get paid $70K per year?

When you go to the password reset page on Amazon.co.uk, it doesn't appear to be a secure page. Maybe the "Save Changes" button submits via an https link, but I don't have time to go digging through the source code - that kinda defeats the whole point of the lock icon, etc, surely?

In any case, the captcha image has been "loading" for about 5 minutes now - guess everyone's trying to change their passwords?

Am I right in thinking that data recovery firms (and government agencies) can pull data off a hard drive, even after it's been overwritten - possibly several times? (Yes, if you overwrite it with random noise, that might make it hard to guess what was there before, but if you just record a normal file or video over the top, that'll have a set of known statistics that make it possible to subtract out and recover the earlier data.)

And if that's the case, why can't they recover the original recordings - which must surely rank amongst some of the most important ever made? It's not like NASA doesn't have the money or the expertise to do this.

Interesting analysis - in particular that you've come up with a figure of 100mW per square meter, which is two orders of magnitude less than most of the other postings assume. You don't make any mention of moving the beam around - surely that would cut power requirements? Signal one 1,000Km stretch of coast for a few seconds, then the next, etc, then return. Maybe enough to knock another order of magnitude off the sums? Which brings your final figure down to 2.3MW (for the Indonesia case, admittedly). Too high for direct power from (reasonable sized) solar panels, but surely the satellite would have some sort of stored energy system; flywheels or capacitors. Would reduce the allowable duty cycle further, but really only need a bright flash every few seconds. To answer your other point: if the satellite happens to be in front of the sun's disc (or even close) you obviously won't see it. But you're going to need a few of these things for coverage anyhow, even in geostationary orbit.

So how is is that people have been able to use mirrors as a means of signaling?

Irrelevant. Not trying to take a flash photo of the land here. How far away is that flash visible from (and bright enough to attract attention) from in front of the camera? I bet it's a hell of a lot further than 30 feet.

So how is it then, then when you have something like the lights on a fire truck, these are clearly visible reflected off the walls of all the surrounding structures, even during broad daylight, even though there isn't anything close to 10W/sq metre incident on those surfaces? I don't envision competing with the sun - like you say, that would take ridiculous amounts of power. But to produce a bright flashing light in the sky? I think that can be done for a lot less power than people here assume.

I'm presuming this scheme was aimed at places like Indonesia, Papua New Guinea, rather than places like Hawaii, which are already well covered. How do you power these sirens in the absence of mains electricity? Would solar-panel-charged batteries still be able to keep a charge after say, 10 years?

I was envisioning not so much an area illumination system, but a "holy crap, that's a bright star, and it's flashing" sort of system - which I think could lower the power requirements massively over actually trying to light up the ground.

I'm not sure about this 10W/m^2 figure. Maybe I just have a different concept to the rest of Slashdot, who seem to be imagining a system that would light up the ground and everything around you. I was imagining a really bright flashing "star". Given that you can easily see satellites with a really small telescope, and that's just using the sunlight reflecting off their panels (say, 1kW per square metre, maybe 1-10 square metres), that I think the power requirements could be way lower than discussed, and still produce an easily visible light. Granted someone in the village would have to be looking up, but I think there's a fair chance of that?

I'd dispute that. If the signal is, say, on for one second, then off for the next, does that make it less visible? You've just halved the average power requirement, and I'd argue the flashing makes it more visible if anything. I think you'd only need a very brief flash to make it visible, particularly if that flash was repeating periodically, so the average power requirement would fall correspondingly.

I had in mind a thin line, 20km long, but only 1 metre wide - one end of the strip at the beach, the other end inland (exact distance depending on gradient of coastline at that point). So that's 20,000 square metres, and I believe that 200kW is achievable with (really big) solar panels.

It's funny, in the recent "How Smart Are You" poll, only 5% of slashdotters rated themselves below average, yet there are some really fucking stupid answers to this post. Read the damn posting people (yeah, I know, this is Slashdot...).

For starters, there are those saying that it would be better to use radar than a laser. You can't see radar, the article's about using the laser for warning people, not measuring the height of the ocean surface.

Then there seem to be a ton of replies along the lines of "it would take gigawatts to illuminate the entire Earth! Sharks with friggin' lasers, etc...".

Who said this thing had to illuminate the entire damn planet in one go? Jeez, ever heard of raster scanning people?

So, it has to warn people in at-risk sections of coastline. That alone cuts the area to be illuminated by orders of magnitude. Then, it doesn't need to illuminate all of these areas simultaneously and permanently - it could sweep them repeatedly. Imagine that the laser was spread out along a line, say 20Km wide, and that then scanned the affected coastlines. So the people underneath might only see a bright flash lasting for say, 10th of a second every ten seconds. Brief, but maybe enough - better than nothing if you're out of range of a siren.

On top of that, you could limit your illumination area so that, at any one time, you're only lighting up sections of coast that are likely to be hit by the approaching tsunami within the next 3 hours, say. Obviously you needn't illuminate any areas which the tsunami has already hit - it's too late for them, sadly.

Come on slashdotters, how about actually engaging the intellect that I'm sure is actually present, and then discussing how this idea *could* be made to work (even if there are better ways), instead of idiotic "terrible idea" comments.