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Comment: Yes: not all infra-red is the same (Score 1) 135

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) 508

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.

Comment: Re:Old news (Score 1) 66

by Richard Kirk (#47605829) Attached to: Animal Behaviour Specialists Map Out the Social Networks of Cows

The article is fine except for this mad bit of hype...

"Now a team of animal behavior specialists have discovered that the social lives of cattle are more complex than biologists had ever imagined..."

This last bit is clearly quite silly: they could imagine that cattle had complex social lives, because they designed an experiment to try and measure the social groupings. They seem to have done a number of sensible things, such as attempting to remove events where cow #1 was close to cow #2 because they were both going for food, or one had to get past the other anyway, or things like that.

Researches reveal amazing facts about cows! The paper that Farmers don't want you to read! Identify cattle with this one weird old tip! You will not believe what cows do when you are not looking!

It could be worse, I guess...

Comment: My weird-o-meter needs recalibrating... (Score 1) 347

by Richard Kirk (#47313901) Attached to: Evidence of a Correction To the Speed of Light

This is a story about the speed of light being not what we thought it was, and involving general relativity, neutrinos, and its one data point from a unique astronomical event. Oh, yeaah, riiight. And yet, it is clearly explained, and stands a good chance of being right. I am definitely going to have my weird-o-meter recalibrated.

The speed of light is the same as it always was. Any given photon may, extremely rarely, split into an electron-positron pair, and then recombine. The electron and the positron are not travelling at the speed of light, so this event will stick in a small delay. If you measure the speed of light over most human experimental lengths, this event will be very rare - so the very occasional photon will show a tiny delay. If your light travels over such vast distances that the photon may have experienced so many of these delays that it spent whole hours as electrons and positrons.

Each photon will have a random number of these delay events, so you might expect the light pulse to get blurred out a bit by this randomness. There will be a slight blurring, but because the number of events is so huge, the fractional deviation from the mean is pretty tiny.

Cute, and neat. Some posters still try and argue for gravitational viscosity, or for faster-than-light neutrinos, or that this is a failure of science and only philosophers can help us now. Ho-hum. Too little fog, too late, chaps. Better luck with the next one, eh?

Comment: Re:Next in pipeline: Honking Humugous Telescope (Score 1) 76

The 'OWL' was the first telescope in this series of names as far as I know. I think all the others since have been given 'OWL' like names.

It's a bit unfair to say the 'OWL' project was cancelled because it was really only a feasibility study, and back in the 1980's rather a bonkers one at that. When people started working with computer-controlled segmented mirrors, it because clear that you could make a huge mirror from almost flat segments of glass. So the next step was to see whether you could make a moving and pointing telescope the size of the Great Pyramid. Over they years that 'OWL' wasn't built, the design was improved and it became clear that it was practical to make telescopes between 20m and 100m. Much bigger than 100m, and you probably have to go into space, to avoid the problems of weight, and atmosphere.

One day they may build the 'OWL' on the Antarctica dome, and you will have the finest seeing of all earth-bound telescopes, ever, and there is no point building any others unless you want to look North. The 'ELT' is a nice compromise: it's in Chile and not down by the South Pole which can be as hard to get to as space, and it's bloody big but it leaves something for our kids to do. Yay.

Comment: Re:What am I missing here? (Score 2) 223

Empty space isn't that empty. You can get virtual pairs of electrons and positrons appearing and disappearing. They pop into existence because they can, even in empty space, but the have negative energy and a virtual wavelength, so they are almost bound to re-coalesce, and the energy of their recombination will exactly equal the energy of their creation, so they pay back all the energy they 'borrowed' and disappear without trace. However, if a photon turns up at this critical moment and pumps in the energy, then they can get permanently separated. Needless to say, this is pretty rare for single photons or we would not be able to see distant galaxies. We need monster photon energy densities, hence the hohlraum (I used to work on these ages ago).

You can also measure a tiny force between two plates in a vacuum due to these virtual particles. This is called the Casmir effect or the Casmir-Polder force. See... for example. So they are real. Well, real-ish.

This is not the same as Compton scattering. That also makes electron-positron pairs from photons but it also requires some mass to be around. This is the dominant absorbtion mode above about 1.5 MeV. So, I can see how they might get a tiny bit of straight pair production in their hohlraum, but they will also have some high-Z gold plasma giving you lots of conventional Compton scattering, which will look pretty similar. I guess they have a plan for that.

Here's a fun site...

Comment: Re:Fragile (Score 1) 33

by Richard Kirk (#46733217) Attached to: AT Black Knight Transformer Hits the Road and Takes a Hop

This actually looks good to me. Most helicopters can be shot down with a rifle. They are huge engines with large fuel tanks and large, whirling blades, and it is not that difficult to get them to destroy themselves with their own momentum, height, or fuel. This thing has eight separate lifting units. I would imagine with the large body, it would not fall that fast, and even if you were missing several rotors it could land in a controlled fashion. The wheels make it look a bit like the chariot from "Lost In Space" but I imagine it could run over uneven ground with computers anticipating the uneven terrain.

I doubt if it is a fast or as powerful as a purpose designed helicopter. However, for something like mountain rescue it would work. You could drive most of the way with lots of first-aid kit, hop over the river where the bridge is down, get to where you are going, dump the supplies to lose weight, fly up the mountain to rescue people, then drive back fully loaded with everyone on board.

Lastly, if you have to use this in a warlike manner, this is a potential solution. You can use bombs, and drones and gas and napalm to clear the ground, but all skirmishes from the bronze age to today are still settled in the field by one lot of people with weapons going over to another lot of people with weapons on foot, and persuading them to give up. The art has always been to deliver your foot soldiers, fresh and well-equipped, in a short hop to the forward position, and get them back if things go bad. This may do it more safely or more cost-effectively than a helicopter if you avoid the temptation to turn it into a long-distance speed-flying helicopter gunship with frickin' lasers () and just stick to the job in hand. This particular beast may look a bit Jules Verne's Armada of the Skies, and it may turn out to be a dog, but IMHO the thinking behind it is sound.

Comment: Nostradamus redux (Score 2) 60

by Richard Kirk (#46472301) Attached to: First Mathematical Model of 13th Century 'Big Bang' Cosmology

I went to the presentation at the Royal Society last week given by this group on Grosseteste's colour theory. Grossteste's papers are very dense and very short, and this one fitted on a sheet of A4. He had a theory about colour that seems to have three clear axes and eight corners. However, he never tells us what the axes are called, or names a single colour, or even tells us where white and black come, which the presenters admitted was 'pretty strange'. There is no obvious algebra, which is correct for the age, but makes it very hard to interpret an unambiguous meaning. Aristotle's theory on colour, which Grossteste would have read in translation from Arabic at the time, has clear experimental models for generating infinitesimal shades between any two colours, and names seven colours - perhaps in an early attempt to see how many colours are needed to mix any colour. In contrast, it is difficult to be sure whether Grosseteste's work is philosophical (which colours should exist), experimental (which colours do exist), or mathematical (how can we model what we see).

Grosseteste was known to be one of the better mathematicians of his age. He is not Nostradamus, pumping out cryptic statements in the hopes that some of them will match something at random. What he said was respected in his day. We have some modern computer model that seems to match what he said to some extent, but only for some small subset of the parameter space. I suspect this tells us more about how we think then about how Grossteste did.

Comment: Re:is there an xkcd comic for this? (Score 2) 138

by Richard Kirk (#46407207) Attached to: The Rise and Fall of Supersymmetry

Experiments are real but the results aren't pretty. SUSY is pretty but the results aren't real.

When we look at the tables of known particles, it is tempting to think of the periodic table. We might hope to see patterns in the particles, and then guess at the missing parts of the grid. Unfortunately, we don't have nice families of halogens, alkaline earths, and so on. We started off with electrons, protons, and neutrons which all had sensible masses even if the electron was less than a thousandth of the mass of the others, and photons which had no rest mass at all. Then we have a very irregular family of subatomic particles including things like mesons, and neutrinos, with finite but stupidly tiny mass. They don't seem to form a family at all, but a lot of clever people invented new sub-particles called quarks, and in the end managed to come up with a plausible theory that seemed to fit a lot of these weirder particles into families. But not everything.

The periodic table was backed up by quantum calculations, which showed why the should be two elements per row, then eight, and then all the transition elements. Unfortunately, we don't seem to be able to finish off the table of the subatomic elements in the same way. We can come up with neat SUSY theories that would work if there are lots of symmetric particles that we do not ordinarily see, but might be more common at higher energies, and bend the various graphs into fitting at some point. However, as the guy neatly tabulated, all plausible versions of the SUSY theory seem to come up with things that we ought to be able to see with the LHC and other things, and we don't. So, right now, and after a lot of people had spent most of their lives fooling with this model, it is beginning to look like we may have gone down a dead end.

Comment: Comments from shipping experts? (Score 2) 216

by Richard Kirk (#46355717) Attached to: Rolls Royce Developing Drone Cargo Ships
So far we have had 100% negative comments in the direct replies, unless one slips past me while writing this. Many of these raise issues that were raised in the original article. Many others just say it won't be safe if computers are in charge. I am not convinced by any of these.

The Rolls-Royce calculations show that there is a measurable saving in pollution by leaving off most of the crew support features. Fine - a potential saving exists. Now let's explore whether the saving is practical

Large ships do not turn suddenly - it can take miles and tens of minutes to turn a large tanker. You do not have to provide the captain with a real-time 360-degree virtual environment. You have to provide some sort of autonomous fail-safe in case communications are lost. You can have a one-time pad encryption for sending instructions, so remote hacking without a copy of the pad should be difficult if not impossible.

What if the ship gets into difficulties? We know the problems that conventional ships get into. It should be possible to calculate what fraction of these could be fixed by the crew at see, and factored into the potential saving. This is what the analysis should do. If you are in a storm, and a conventional container ship starts spilling its load, there is probably not much the crew can do other than hang on and wait for the storm to pass. It seems entirely reasonable to me that a small number of faults at sea could be fixed by flying out personnel to the ship and landing on the flat top of the containers, if nowhere else. So, you factor in the costs of a call-out.

Might work. Won't ever work if no-one's prepared to think about it, though.

One possible reason that things aren't going according to plan is that there never was a plan in the first place.