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Comment: The consumer will never be ready (Score 1) 229

by Richard Kirk (#49454183) Attached to: 220TB Tapes Show Tape Storage Still Has a Long Future

Tapes have never gone out of use for large databases. The tape storage is cheap per bit compared to other formats. We know the life of a bit on tape is finite, and we know the random access time of tape is horrible. However, suppose you are providing a reliable backup service. You will have at least three copies of every record at any time, with probably a fourth archive kept separate for legal reasons. Ideally, the three copies will be in different geographical and economic zones, so you can survive the total loss of one. You will be checking these copies against each other and re-writing the data onto fresh media at regular intervals. You know the archive is good because you have a scheme for checking it and re-writing it at regular intervals. If you compare a tape in an actively maintained archive against a hard disc you keep on a shelf and never read, then the tape archive will probably be the safer of the two.

Tape is not really a consumer product, even if the tapes and tape readers are affordable . I doubt if many consumers have the discipline to maintain their own archives to this standard. I know of several good-sized companies that have kept tape archives that turned out to be no use when they had to be read. I long for the day when crystalline molecular memories will give us moles of stable bits in a few tens of grammes of material. But until then, tape seems to work.

Comment: Not having a mobile phone is suspicious... (Score 3, Interesting) 89

by Richard Kirk (#49145901) Attached to: OPSEC For Activists, Because Encryption Is No Guarantee

Any pattern in the way you behave can be used against you. If you are not emitting a mobile phone signal, then you are suspicious. If you have an iPhone, and the logs suggest you regularly take the batteries out, then you are very suspicious. A modern spy would carry a mobile phone - not the latest security recommended one, but something dull - and would tweet and post pictures of what they are eating and listening to just to get the right watch profile. You would have to leave the phone behind when you want to do Spy Things, but you could leave it in the locker at the swimming pool, or something plausible like that. If you have to send crypto messages over this phone, keep the message very short, and plausible.

I don't think there are many real spies here on Slashdot, but there are probably people who would like to keep their data secure in a way that does not attract attention to themselves. Perhaps we should all use encryption whether we need it or not, so those that need it will no longer stand out.

Comment: Use Saturn's rings (Score 1) 126

by Richard Kirk (#48922553) Attached to: Proposed Space Telescope Uses Huge Opaque Disk To Surpass Hubble
You don't just want a circular object. You want a series of circular rings at the right intervals to interfere and give an intensity peak where the camera is. This s not as efficient as using a giant mirror, but it could be a lot lighter, and less sensitive to vibrations or distortions out of the plane of the disc. Saturn has a lot of rings. The shepherd satellites within the rings make some pretty complex patterns. It may be possible to use the natural structures. Or maybe we could add a few small moons of our own. The camera would have to lie above or below Saturn to look at the unlit side of the rings.

Comment: Re:In other news... (Score 4, Insightful) 154

by Richard Kirk (#48809741) Attached to: Human Language May Have Evolved To Help Our Ancestors Make Tools

Yes, this is how science works. It is obvious that talking will help people make flint tools. We all know that. But how do we know that? Saying 'it's obvious' is not helpful. It is also obvious that you can get better at making tools when you can watch someone who is good at it. But you can get plenty of people how have never chipped flint tools, and see how much better they are when they watch someone, when they mutely interact with someone, and when they talk. Some gifted people can pick up musical instruments just by watching, but making flint tools seems to be helped a lot by language.

The article also says that this is suggestive, but could not be considered a proof. They know they have not got ancient people to experiment on. It is not practical to try the same tests with a mammoth hunt. It's not a time machine, but we use what we have.

Then you get a +5 'insightful' mark-up for jeering at it.

Comment: Structure in plasmas (Score 1) 300

by Richard Kirk (#48752957) Attached to: The Search For Starivores, Intelligent Life That Could Eat the Sun

It's a high energy plasma out there, how will you get any structure in that?

Actually, the sun has a lot of structure in its magnetic field. This is not just complex in the way Earth's weather is, meaning is is unpredictable. It has long term structures, such as the 11-year sunspot cycle.

I really doubt if these magnetic fields are sentient at all, and certainly not sentient as we understand it. The world's phone system has a similar complexity to the human brain, but if that was sentient, it would be hard to imagine what it thought about, as it has no obvious eyes and ears.

However, suppose we wanted to delay the supernova of our sun. We could do this if we had the technology by injecting fusible hydrogen from the sun's surface into the core at the same rates that it was consumed. This would require completely bonkers apparatus, but the physics is good. Supposing the best and most efficient way of doing this was to influence the magnetic field of the sun so that it did this itself. Suppose the best way of doing that was to artificially induce intelligence in these plasma fields, so it could do this without regulation...

That is a lot of supposes. But in my mind, I think if civilization lasts for astronomical time-scales, this is less ridiculous then expecting to detect them by their leaked unfocussed long-period radio waves, which is what SETI is looking for. I wouldn't spend any money on it, but the thinking doesn't hurt.

Comment: Thin lens formula (Score 2) 464

by Richard Kirk (#48725011) Attached to: Ask Slashdot: Are Progressive Glasses a Mistake For Computer Users?

Remember 1/object_distance + 1/image_distance = 1/focal_length ?

If you have your screen at R meters away, add (1/R) to your lens strength in diopters. Diopters are 1.0/focal_length in meters. That will give you the same comfortable image_distance at your eye when looking at your screen.

Suppose you have your monitor 0.5 of a meter away, and you use -5.0 diopter glasses because you are short-sighted. You add (1/0.5) = 2.0 to -5.0 diopters and get -3.0 diopters. The person who had -5.0 diopters and used -3.5 diopter lenses for computing work probably uses a screen 2/3 meters away. If you are short-sighted, the diopter values should get smaller in magnitude; if you are long-sighted, the diopter value will get bigger.

Add 2 diopters if your screen is 50 cm away.

Add 1.5 if your screen is 67 cm away.

Add 1 if your screen is 1m away (a bit far, but maybe you have a big monitor)

Hot damn, that school physics is actually good for something! Too bad they had to black out the lab to show us, and we all fell asleep. Now, all I need is some frictionless pulleys and massless string...

Comment: Re:No bigger than ... (Score 3, Insightful) 325

by Richard Kirk (#48546077) Attached to: Heathrow Plane In Near Miss With Drone

Bird strikes can be dangerous if one goes into the engine. This rarely downs an aircraft unless you have a two-engined aircraft and both engines get hit at the same time. Remember the plane that landed in the Hudson after a double bird strike? That was an Airbus A320.

Whether this is a significant risk depends on what the drone flyer is trying to do. If they are trying to get close-up pictures of aircraft then they are probably no bigger risk than birds. If they are aiming for the engines because they want to take down an aircraft, then there is a significant risk, particularly of the drone is carrying some load designed to do damage. Why would someone do this? I dunno. Why do people use laser pointers to try and blind pilots? Maybe not terrorism: some people are just dicks.

What do we do? Well, if they are radio-controlled then we can pinpoint the controller by radio. It would be a nice problem to design a set of drones that can triangulate the source of a radio signal, home in on it, and track what they find.

Comment: Yes: not all infra-red is the same (Score 1) 145

by Richard Kirk (#48478411) Attached to: Scientists Develop "Paint" To Help Cool the Planet

The actual article is a bit shallow on detail, but here's my interpolation...

Infra-red is quite a broad bit of the spectrum. It starts at about 800nm as light we can't quite see, and security cameras use this band with an infra-red illuminant. If we go down to about 2000nm, we are into the mid-band where some IR cameras operate. These can see hot objects but cannot people by their radiated body heat. There is a gap at about 3500nm where water vapour absorbs and emits, and cameras do not work well. Then there is another band at about 7000nm where the thermal cameras that can pick up body heat work. The cooler you are, the greater fraction of long wavelength you emit. (NB: if the exact wavelengths are important, please check as I am typing this off the top of my head).

Most black paints absorb all infra-red wavelengths equally. Some white paints will absorb the far-infra-red. What you want, and what I think they have done is to make somethng that reflects down to 2000nm, and then absorbs beyond about 400nm. This will reflect a lot of the heat from the sun, but will still radiate the heat from the building.

Does it work? Will it still work when it is dirty? I don't know, but at least it does not violate any thermodynamic principles.

Comment: No easy fix? (Score 1) 516

by Richard Kirk (#48466017) Attached to: Ask Slashdot: Why Is the Power Grid So Crummy In So Many Places?

I live in a large village or small town. I get a lot of power outages. Some of these last for hours. Most of the rest of the village does not get these - just a small clump of houses around the church. Our cable comes underground from Hemel Hempstead. The rest of the village gets power from the pylons that run alongside the M1. We can claim back money for the power outages.

I would imagine our group of houses has problems because (a) we are at the end of a spur (b) we got electricity before anyone else, and before the M1 was built, so our lines are particularly old, and (c) the power distribution network has probably shifted, and our little bit has not been altered to reflect the changes. If you live out in the sticks, you become more vulnerable: I remember a house where the power used to trip out when the transport cafe about a mile away turned off their grills last thing at night. One of the downsides of generating your own power may be that the network only has to fill in when we have a number of dull, still days. The US equivalent is probably hot days where everyone turns up the airconditioning.

It is not because (a) our lines are overhead, or (b) our corner of the village is particularly greedy, or (c) that the power company does not have to pay when services are disconnected. Beware of people suggesting 'obvious solutions' without evidence.


Comment: Are we measuring the brain or the blood supply? (Score 1) 91

by Richard Kirk (#48344475) Attached to: fMRI Data Reveals How Many Parallel Processes Run In the Brain

The scanner measures the hemodynamic response function. The brain only sends oxygen-rich blood to the regions of the brain that need it. I guess this restricts power consumption, heat sinking requirements, and so on, a bit like the power limiting circuits on a processor. It is likely that the power regulation is a lot less fine grained in the brain than the thinking process itself. So if you had two separate regions that were fed by a single blood supply, you would not be able to distinguish them. In practice, I expect the processing regions and the blood supply regions have fuzzy borders, and there is a limiting return in micro-managing the blood supply.

I do not understand the gas station analogy. To me, this is more like trying to tell how many people are in a building by how many lights are on. You can subtract the permanently on lights from stairwells and corridors. You can then assume a light that goes on, and goes off may be a single person, or a meeting, or a group of people who all come and go at different times. Subtract the lights that are permanently on, and you would expect the person could to be at least the remaining light count, because several people may use the same light.

Hey, it's a start.

Comment: Old Mac (Score 2) 334

I gave my mum (95) an old PowerPC laptop I got for the price of buying a replacement power supply. It is running a version of OS that probably is no longer updated, but turning off automatic updates doesn't hurt.. I have also stuck on an Applesript that e-mails me when the machine powers up, which she does every morning to let me know she is OK. She is probably a bit less click-happy then your users.

Comment: 70% successful prediction (Score 1) 177

by Richard Kirk (#47621327) Attached to: Algorithm Predicts US Supreme Court Decisions 70% of Time
A 70% prediction rate is not impressive. In the UK, where the weather seems pretty unpredictable, "it will be pretty much the same as yesterday" is right about 70% of the time. Weather forecasting and track individual storms, but It took a long time and a lot of research for the weather forecast success flat rate to get any better than this. The model may be important: the success rate probably isn't.

"But this one goes to eleven." -- Nigel Tufnel