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Will it be as reliable as when they automated the baggage handling in Denver Airport. How will the driverless cabs respond to unplanned events like breakdowns or an obstruction. I once asked the conductor on the driverless docklands light rail what happens if there's an obstruction. He replied that well then we hit it.

See Formal Methods Virtual Library for more info on Formal Methods.

My guess, "real" programmers still use print statements.

... now, i'm trying to printf my Gmail account with mails! ...
-- br

the Transputer. It had 4 available hardware connections and the description of the way the different processors communicate is very similar to what is described by the article.

Of course to take maximum effect of this communication speed in general parallel applications, main memory access would have to be improved. I'd guess these things will have huge on-chip caches.

When Inmos was selling transputers, they published some results (in Byte Magazine I think) that had one of their programs running on 4 processors at 4.4x the speed of it running on 1 processor. This trend continued up till 7 processors (where it dropped below an extra 1x per processor added). It does really depend on the type of calculation you are doing.

Also, letting the OS have time on a different processor than my app is running is a good thing.

Because the margin of error in software ~=0.

I can build a house, make the walls nice and think, put some good solid oak timbers for rafters etc... and expect it to last a couple of hundred years without any magical training.

in software, one typo could be the differance between life and death.

In critical systems they usually get two different groups of people to software for the same task on different hardware and hope that they both didn't make the same mistake.

No need to be rude...

I imagine that most of you know the ideal gas law, ie that pressure and temperature are (almost) linearly related. So, if you increase the pressure, you should be able to melt snow or ice, right? If it gets colder, you just squeeze harder. This means that warm snow should be slipperier, since you can melt more snow, which will lubricate better, right?

Unfortunately, below 30 degrees Celsius or so, there is no way to get water, no matter what pressure you apply. Look at the following ice/water/vapour
diagram. You will notice that vapour and liquids don't take up much of it, it's ice almost everywhere. And all ice below 240K (=-33C) or so.

So how could we possibly ski at below -33C? The answer is that we just slide on the snow. Occam's razor, ya?

I read about that in a book (The Armchair Universe by AK Dewdney, I think), I don't know if it's on the web anywhere.

Oh, /me actully looks... Check here: http://www.scism.sbu.ac.uk/inmandw/review/nlp/revi ew/rev4987.html

Pretty much correct, except for a minor nitpick. By looking at the Phase Diagram for Water and the Atmospheric Pressure on Europa (10^-6 Pa), you would only need to warm the ice to about 210 K, or -63C. That saves about half the work that you implied (but granted it'd still require some decent energy to accomplish).

You've not been reading enough of the articles then. See eg this one. The Myna pager is definitely a 'consumer market' device. I'm sure I read Ivan Sutherland say somewhere that there are asynchronous islands on the latest SPARC chips, but I can't find a reference.

However you're right, takeup is minimal, see eg this talk for a description of the state of play.

Another approach that may have gone the way of the dinosaur (havent seen it make headlines on /.) is reversible computing - the notion that by not discarding information within a chip you can run chips cooler (though apparently we won't reach the level where this much thermal loss becomes significant for another few years). E.g. a nand gate loses one bit of information, resulting in an energy dissipation of at least ln(2)kT, about 3x10^-21 joules. These links are 4 years old; I have no idea if reversible computing is now mainstream?

This kind of chat-bot program has been around for a long time. I had RACTER on my PC, and it was pretty good. You can read some snips of RACTER and ELIZA duking it out.

1. The picture is an artist's rendition (look at the caption under the picture to the right of the article). The article doesn't say how the nebula was observed, but it's entirely possible it was not using visible light at all but IR, UV, XRAY, whatever (I'm no astronomy expert, but I know they don't always limit themselves to the visible spectrum). The water could have been identified from any number of known absorption lines.

2. The water in question here is probably not liquid water. The article constantly refers to the star spewing "water molecules". Although the incredibly hot water coming from a star probably cools enough to liquify, it's still probably not dense enough to form liquid. If you were out there in a spaceship looking at this star, my guess is you wouldn't be able to see these plumes. Sensitive astronomical equipment, however can see things you can't. Again, this is an artist's rendition.

3. Liquid water is actually blue, and not just from the sky. It absorbs red light a little more than it absorbs blue light. A glass of water absorbs too little for you to see, so the water looks clear. 60 ft of water absorbs enough red light that everything you see looks blue or green. A quick google search turned up this link. http://www.sbu.ac.uk/water/vibrat.html The discussion is pretty technical, but about halfway down the page is a nice graph showing water absorbtion vs. wavelength, with the visible spectrum colored in for reference.

4. That said, your point about the sky and reflection is not completely wrong. When you look down at a body of water (as opposed to swimming around under water), most of the light you see is reflected off its surface, and the water will appear similar in color to the sky, regardless of what colors it absorbs. And so, yes, if that were liquid water coming out of the nebula, and that were a real picture, "red" water could still be very easily explained if the nearest source of light were red (like the nebula as it's drawn in the picture).

Seems like if they could make the probe kinda warm it would eventually sink through any amount of ice.

That's a bit of an understatement. Let's do a quick calculation, shall we?

The article says that the ice is at least 19km (11 miles) thick. Let's assume we can somehow magically make our probe fit into the volume of a square foot or 30cm per side. That means we have about 1700 square meters of ice to melt, which is around 2e6 kilograms.

Europa has no real atmosphere, the pressure at the surface is around 1e-11 bar (1e-6 Pa) -- i.e. almost nothing. So the ice would most certainly vaporize rather than melt, and at a temperature lower than 0C. See this neat phase diagram of water. As we go down farther the pressure will necessarily increase, but I don't feel like calculating it exactly. Based on the phase diagram I'll use 200K as the approximate transistion temperature. It's close enough to be within an order of magnitude of correct.

The surface temperature of Europa is approx -260 dF (111 Kelvin), so to raise it to 200K results in a temperature difference of 89K. The specific heat of ice is around 2e3 J/(kg*K). That means our task will require about 3.5e11 Joules of energy. Let's say we let this process take 100 years at a steady rate. This comes to about 111 Watts. Suddenly "kinda warm" really doesn't cut it.

When you have a self contained source of power that can supply 111 W constantly for 100 years and fit into a square foot of volume, please let me know. Surely, you would have solved our energy crisis by now.

PS - Solar panels are pretty much useless after you get farther from the sun than Mars. That's why probes like Cassini needs radio-isotope thermo-electric generators.

Testing is critical.

Others would argue that testing alone may not suffice. Particularly for these kinds of mission critical applications, nothing short of formal methods of software engineering will suffice. Formal as opposed to natural language specifications can reduce ambiguity. Safety conditions can then be derived and verified through rigourous mathematical proofs.

Of course none of this obviates the need for testing but it can lead to a more predictable system.

Project Phoenix??? You would think they could choose a more reasuring name for hydrogen powered aircraft, given people's perceptions!

Of course, by now it's also a bit of a cliché...

After all, ice doesn't necessarily have to be water.

-B

Earth's atmospheric pressure is 1 atm or converting to kPa, 100 kPa. Martian atmospheric pressure is about 1% of Earth's or about 1 kPa (10^3 Pa on the chart). Average Martian surface temperatures at the equator are -53C or 220K. Now looking at our chart again, we see that at this point, water cannot exist as a liquid, but only as a solid (ice). As day/night termperatures shift, water will alternate between solid and gas only, never even passing through the liquid state, and once a gas, not likely to collect on the ground, but remain suspended as ice crystals high in the air. So for now, the collecting frozen water from near the poles, storing it in canisters , and transporting those to any camps remains the only realistic wat of getting water on Mars.