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That isn't correct. While in a reactor Plutonium, or Uranium (fission) will produce more energy than fusion per nucleon, that is the average energy over the life of all of the decay products:

http://periodictable.com/Isoto...

The majority of the decay products takes far longer than a full second to be produced, so they aren't relevant to the detonation, or the brisance of the device.

http://www.kayelaby.npl.co.uk/...

In the environment of a reactor, you can simply wait long enough, and extract the full energy as Plutonium is converted between a dozen different elements, but in a bomb, speed is king, so the slow fission products don't add meaningful amounts of force, or power to the explosion. Fusion boosters don't have a critical mass, so you can pack in as much of them as you want.

Ref. It took 30 seconds. Please don't ask other people to use Google for you, you're (presumedly) an adult and should be able to manage these sort of things on your own.

But in order to avoid thermalizing your fission fragments the reaction is going to need to be in near-vacuum

The reaction is done in a near vacuum. But that doesn't mean that there's almost no fuel. Fission fragments and neutrons behave totally differently, fission fragments are positively charged and respect Lorenz force, neutrons are neutral and do not, so it's easy to separate the two (as well as from the fuel, which becomes negatively charged and is not moving at relativistic velocities).

These things have been fully simulated, there's nothing unreasonable about them.

but our best neutron mirrors can only get total reflectance at angles of incidence of less than a single degree

I have no clue where this is coming from. Neutron reflectors (more properly thought of as scatterers) can scatter back, and in fact moderators produce a relatively anisotropic thermal neutron flux. The current proposal for a dusty fission fragment reactor involves U235 fuel and a moderator in the shell of the reactor.

I'm pretty sure, that outside of the US, Joe Public doesn't even know WWVB exists, which is a shame as a single standard global time signal (back in the day) would have been kinda cool.

Here in the UK we have something similar (even runs on the same frequency):

http://www.npl.co.uk/science-technology/time-frequency/products-and-services/time/msf-radio-time-signal

http://en.wikipedia.org/wiki/Time_from_NPL

It's referred to as the 'Rugby clock'.

-Jar

Historical definitions and modern definitions have little in common. The historical definition of the meter was 1/10,000,000th of the distance from the equator to the north pole along a certain longitude line. The modern definition of the meter is based on the distance a certain wavelength of light travels in a perfect vacuum in a measured amount of time. That's (indirectly, through the meter) the modern definition of an inch, too. It just happens to be a different measured amount of time. See http://www.npl.co.uk/reference/faqs/on-what-basis-is-one-inch-exactly-equal-to-25.4-mm-has-the-imperial-inch-been-adjusted-to-give-this-exact-fit-and-if-so-when-(faq-length)

But I bet a microphone could still pick it up..

I don't know... might work better than radio waves - the attenuation of RF in air might not beat the attenuation of sound waves. The higher the frequency, the higher the attenuation of the ultrasound in air (dry air: 0.6 dB/m at 50 kHz, 1.8 dB/m at 100 kHz). Add some directional elements, use a small emitting power and what's not in direct line of emission might be drowned by noise at a distance of 0.1-1m.

And, on a side note, this is oddly reminiscent of Phreaking

Hmmm... yes, but I think in this case the danger will come from rogue bats flying around that pay terminal (hold you fire, it's just a lame joke)

Why would you want to give a kid a ruler with inches on it in the first place?

To be serious, all decent science programmes do use SI units including the US government and UK government.

Of course, engineering, construction trades, and commerce in some countries still see common usage of non-standard units in popular (lay) life.

Helium-3 fusion would be nice, but it's even harder to do than DT fusion.

http://www.kayelaby.npl.co.uk/images/p548.jpg

Look at the curve that says DT, and compare it to the one that says 3He-3He. Note how you need twice the temperature to reach half the reaction rate.

In my view, we've got to build DT fusion reactors before we can even hope to make helium-3 ones.

The total mass of the oceans is about 1.4*10^21 kg. The total mass of the atmosphere is about 5*10^18 kg. That means the oceans weigh about 300 times as much as the atmosphere.

The heat capacity of water is about 4000 J * kg ^ -1 * K ^ -1. The heat capacity of air is about 1 kJ * kg ^ -1 * K ^ -1, or about 1000 J * kg ^ -1 * K ^ -1.

So since there's 300 times as much water as there is air, and the heat capacity of water is 4 times larger, heating up the atmosphere by 1200 degree Celsius would take the same amount of energy as heating up the oceans by 1 degree Celsius. This may not prove or disprove your point, I just started thinking about numbers when you said "raising the temperature of a body of water by a few degrees".

Except we don't know exactly what raising the temperature of the oceans by one degree will do.

The total mass of the oceans is about 1.4*10^21 kg. The total mass of the atmosphere is about 5*10^18 kg. That means the oceans weigh about 300 times as much as the atmosphere.

The heat capacity of water is about 4000 J * kg ^ -1 * K ^ -1. The heat capacity of air is about 1 kJ * kg ^ -1 * K ^ -1, or about 1000 J * kg ^ -1 * K ^ -1.

So since there's 300 times as much water as there is air, and the heat capacity of water is 4 times larger, heating up the atmosphere by 1200 degree Celsius would take the same amount of energy as heating up the oceans by 1 degree Celsius. This may not prove or disprove your point, I just started thinking about numbers when you said "raising the temperature of a body of water by a few degrees".

Is there a place to check this? I found the article you're talking about - but you have to buy it to read it. The reference can be found here.

I worked on a project at the UK National Physical Laboratory http://www.npl.co.uk/ in the mid 1970's. A couple of applied physists had played around with a graphics tablet and come up with a graphical scheme for authentication. My job was to turn their code into algorithms and write a specification to be used in their patent application.

Their idea of an NDA was the Official Secrets Act, so I won't go into any details.

This entire story (which has appeared on a lot of general news sites, but no science news sites) is probably just a case of a reporter misunderstanding something a scientist said. According to the UK NPL site, fluctuations in the physical objects used to define fundamental metric units has always been a problem. Back when they were created, the ideal material for them seemed to be a hard, dense iridium-platinum alloy. This turned out to be a nasty mistake: the alloy is slightly radioactive, which means that some of its mass flies off into space all the time. No mystery there.

This is why most fundamental units are now based on natural constants. For example, the meter used to be the distance between two notches on a platinum-iridium stick. (Before that, it was defined as 1 ten-millionth of a line that goes from the equator to the north pole; except they miscalculated the length of the line!) Now it's based on how far light travels in some tiny amount of time. But there's no consensus as to the best way to get rid of the physical kilogram.

In other words, all we have here is a clueless reporter trying to fill up a slow news day.

And I cleared up my sig so you'd understand it better, which you dont because your still trying to be an english teacher. Get your Masters then try and correct me. Stop trying to sound smart about that which you have no idea.

The latest NIST work [...] confirms the institute's 1998 results using the same method while reducing the measurement uncertainty by about 40 percent, thanks mainly to improvements in the hardware used in the experiments.

No, it's widely accepted as a necessary step towards being able to define the unit of mass in terms of a specific number of carbon 12 atoms. Look, it would be a lot better for this discussion if you made the effort to learn what the project was for.

Just because you personally don't understand it doesn't make it "media spin" or otherwise redundant. There's more information here http://www.npl.co.uk/mass/avogadro.html, including an FAQ which might clear up some of your misconceptions.

This table would seem to support the #3 status.

According to the FAQ on the NTP homepage "NTP uses UTC as reference time"

Further down there is a discussion of how leap seconds are handled. I was curious so I checked my computer clock (which is synced using NTP) against my alarm clock (which uses the radio signal from the MSF service and they are the same. So it seems that NTP must have observed leap seconds contrary to your original post.

By a 'real vacuum wouldn't have a bow shock' I take it you mean total/complete vacuum, which I think of as included as one end of the spectrum of vacuums that I would call 'hard'

A "Magneto-optical trap".

http://www.npl.co.uk/quantum/projects/project1-1/m ot.html [npl.co.uk]

one of my fav physics tools because it uses lasers and magnets! it's just so science-fictiony!

Ah, but you should have seen the new device they're using to mix micromolar quantities of ligands that I just saw - it's got three input dispensers on a head at angles, a top mixing chamber, and then a long thin tube which is heated by microwaves.

It actually looks like the Romulan Cloaking Device after installation ... kind of tech.

A "Magneto-optical trap".

http://www.npl.co.uk/quantum/projects/project1-1/m ot.html

one of my fav physics tools because it uses lasers and magnets! it's just so science-fictiony!

----
Check out my music video!

Rugby Radio Station
At the end of March 2003 Rugby Radio station sent its last commercial message when the 16kHz GBR transmitter was taken out of service.

This was the original service that the station opened with in 1926 and for which the very tall masts were built. Its high power and low frequency enabled it to contact virtually anywhere in the world. It was used initially for sending telegrams in morse and later telex messages, but was never intended to send speech, unlike the other transmitters on the site. The original transmitter was replaced in 1966.

Telephone services started on other transmitters in 1927 and as short wave services developed the site east of the A5 was opened from 1953. Short wave transmissions stopped in 2000 when communications with ships moved over to satellite.

The Rugby Radio Clock transmitter remains in service under contract with the National Physical Laboratory.

The meaning of "weight" is ambiguous between "force due to gravity" and "mass". In commerce, it has always referred to mass. (If you want to measure the quantity of something, you balance it on some scales against a known reference mass. Force can't be measured nearly as accurately or conveniently with simple equipment.)

You were probably thinking of a "pound-force" (symbol lbf), but that is a deprecated unit with no precise formal definition -- since it would have to depend on some arbitrary average value of g at the earth's surface. Sometimes a conventional value of g is used that comes out to 1 lbf ~= 4.448 222 newton, but that's not a standard.

The meaning of "weight" is ambiguous between "force due to gravity" and "mass". In commerce, it has always referred to mass. (If you want to measure the quantity of something, you balance it on some scales against a known reference mass. Force can't be measured nearly as accurately or conveniently with simple equipment.)

You were probably thinking of a "pound-force" (symbol lbf), but that is a deprecated unit with no precise formal definition -- since it would have to depend on some arbitrary average value of g at the earth's surface. Sometimes a conventional value of g is used that comes out to 1 lbf ~= 4.448 222 newton, but that's not a standard.

Dizzle wrote: Now, I know those definitions are techincally correct, but who thinks these ideas are easily applicable? I mean, the point of having a definition is to be able to calibrate everything else, right? So how on earth is a watch manufacturer or repair person going to say "alright, the cesium atom vibrated 9,192,631,769... 9,192,631,770 times. That's a second."

Is there actually a method of directly using these definitions?

National standards laboratories, like the UK's NPL, use these definitions to calibrate standards for their own use and for that of commercial calibration laboratories. It's a lot of work, but it's reproducible and doesn't depend on any particular set of instruments. The watchmaker's equipment may be another couple steps removed from this process, but ultimately any instruments of any real accuracy can trace their calibration back to a reference standard somewhere.

Oh, it really was a vacuum. Once I got it off and cleaned it, and put a tiny amount of grease back on, it formed the vacuum again instantly, and required several minutes of coaxing to come off again.

I don't think it's air trapped in there per se, it was warm when I originally took it off. You don't need air bubbles to have a vacuum.

Have you ever seen a machinists gauge blocks? They are very polished and flat metal blocks. If you stick two of them together, the lack of air between them actually makes them stick together. I think it's a similar effect here. If air can't get in, then it's a vacuum. :)

While MS Excel may have an extensive array of features it is somewhat lacking on the accuracy front. At least as far back as Sawitski (1994) various scientific analyses have been critising Excel using phases like "can be judged inadequate" and "it can be deduced that Excel uses an unstable algorithm". However as McCullough & Wilson (1999) note Microsoft has done little to address these concerns. The problems Sawitski found in Excel 4 were still present in Excel 97 and Excel 2000 for that matter. In fact critisism of the accuracy of Excel 2002 and XP in the scientific literature continues e.g. McCullough & Wilson (2002).

To quote the The Gartner Group, "Enterprises should advise their scientists and professional statisticians not to use Microsoft Excel for substantive statistical analysis". Of course if you do not need to do accurate statistical analysis then these problems will not effect you but given that Microsoft knows about and has largely ignored these problems and scientists are the people most likely to check that a given piece of software really does what if claims to do rather than using it blindly, it seems quite possible that similar problems exist in other parts of Excel but have yet to be exposed.

Rather than blindly copying Excel, the Gnumeric team might do better by trying to bring on board some of these scientists who have been testing and critising Excel in order to improve the accuracy of Gnumeric, so that not only does Gnumeric beat Excel on features but also, and far more importantly, on accuracy. See the following links for more info on the problems with Excel, 1, 2, 3, 4.

Is there any physical reason (other than that small matter of cost ) that crafting a new kilogram (or more likely, gram) out of diamond would not be an ideal solution?

BTW, theNational Physical Institute has a FAQ on its Pl-Ir standard kilo.

Their reasons are right there in the article.

Stalagmites and craters

By examining the surface of hundreds of alloy plates under an electron microscope, NPL has discovered where previous researchers went wrong. It has developed a two-stage technique that produces the blacker black New Scientist saw emerge from the acid tank last week.

In the first stage, an object to be blackened is immersed for five hours in a solution of nickel sulphate and sodium hypophosphite. This produces a nickel and phosphorus coating containing between five and seven per cent phosphorus. Then the surface is etched with nitric acid to produce the super-black surface structure.

One of the crucial discoveries, says Brown, was how the percentage of phosphorus in the nickel coating affected the surface after etching. An electron micrograph of the surface of an alloy containing more than eight per cent phosphorus (see graphic) looks like a collection of stalagmites.

But if the phosphorus content is around six per cent the surface becomes pitted with craters. The curved craters reflect less light that the straighter-sided stalagmites, so super-black reflects about half as much light as the high-phosphorus surfaces.

Right angle

Super-black is especially effective at absorbing light that hits it at an angle. With the light source at right angles the super-black coating reflects less than 0.35 per cent. Black paint, by comparison, reflects about 2.5 per cent, or seven times as much. With the light source at an angle of 45, black paint reflects 25 times as much light as the super-black.

NPL Super Black In order to make accurate measurements in the UV, IR and visible regions, optical instruments and sensors need surfaces with very low reflectance. These black surfaces are used as efficient radiation detectors or may reduce stray light in an instrument. Highly efficient black surfaces allow smaller, lighter instruments to be made, which is an important advantage in aerospace applications. NPL has successfully developed a very high quality optical black ] known as NPL Super Black. The process uses an adapted nickel phosphorus electroless plating technique followed by finely controlled etching and gives probably the blackest surface known in the visible region. NPL has successfully and repeatedly produced the Super Black coating on a small-scale ecottage industryf basis for a number of years. It is now for upgrading and validating the process for plating much larger substrates with this high quality optical black. The upgrade has led to an opportunity to collaborate with CNES, Astrium and Sodern, the major space contractors for the European Space Agency, on the space evaluation of the black. If successful this will open up many new opportunities for supplying coated optics to the aerospace industry.

Highly Absorbing Surfaces for Radiometry

An actual link

Microwave Phase Conjugation using Discrete Superconducting Elements for Retrodirective Antenna Applications

IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 46, NO. 11, NOVEMBER 1998 Microwave Phase Conjugation Using Antenna Arrays


Microwave Phase Conjugation Using Artificial Nonlinear Microwave Surfaces


A Retrodirective Array Using Balanced Quasi-optical FET Mixers with Conversion Gain

What you think Alan Greenspan doesn't use Excel??????

I hope not! Excel demonstrably cannot calculate a
standard deviation see here.

Now find a way to define temperature and you're done.

Simple.
"The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water." (http://www.npl.co.uk/npl/reference/temperature.ht ml)

The NPL (UK version of NIST) tested a variety of software used for scientific purposes, some of the results are in Metromania 13.

The NPL (UK version of NIST) tested a variety of software used for scientific purposes, some of the results are in Metromania 13.

I have no idea whether OpenOffice suffers similar flaws. Perhaps I'll get ambitious enough to run some of these tests on it myself, someday. In the mean time, I do my number crunching in R. I find that LaTeX provides far more professional-looking reports than any combination of MS products.

There's a radio signal that's broadcasts the exact time that some alarm clocks use: the UK one is at Rugby, but there are equivalents worldwide.

Lol... funny you should say that :-

According to the US Navy :-

"In 1958 the Naval Observatory and Britain's National Physical Laboratory published the results of joint experiments that defined the relation between Atomic time and Ephemeris time. (An interesting scientific and philosophical question is whether the relationship between Atomic time and gravitational time remains constant.) Since 1967 the international definition of the second has been based on these joint experiments. Atomic time is kept synchronized with universal time by the addition or subtraction of a leap second whenever necessary."

According to the NPL :-

"It was Louis Essen's research into the physics of frequency generation and measurement that changed the way the world measures time. In the 1930s he worked on the first quartz oscillator-based clocks and by the 1950's he had devised a caesium atomic-beam tube which could be used as a clock. This led to a better definition of the second using the world's first atomic clock, built at NPL in 1955."

And the Canadians

"A method to replace astronomical observations was urgently sought. The atomic clock, first developed in Britain, was the solution. Scientists at the NRC made a Cesium atomic clock (Cs I) (660528), which went into operation in 1958."

When it comes to British inventors/inventions this is all too common occurrence, there is some great innovation in the UK but traditionally they concepts aren't followed through to commercialisation.

It happened to Sir Frank Whittle and the jet engine and consequently the first supersonic fighter, the Bell 1 which was based on the British design after the British Government withdrew funding for the project.

There was also the debacle over public key crypto research at GCHQ.

Donald Davies worked a the National Physical Laboratory in Middlesex, unfortunately the British Govt/Grants agency didn't see the potential of the invention at the time and no funded was given, so he went over to APRA who were throwing money at anything.

Donald died June last year at in Australia, where he went to retire, he didn't get a lot of recognition outside of a few small circles, but he did get quite a few awards from the various computing institutions in the UK, I think he's still relatively unknown in the US, probably because he was too modest, which is why some many scientists can claim to have invented Packet Switching.

I admit I did not know that. Here's a good link, for those who are interested. Personally, at the point where I need lots of significant digits for my regression fits I'd use real statistical software but your point is well taken.

I've battled with the VBA environment in Excel before, and it flat-out sucks... it's crash happy, slow and frankly dreadful.

I don't have the slightest idea about that. Still, for what I use Excel for -- and that's far more than making tables -- it performs really well. If the free office suites could touch it in quality, usability and polish, Linux would be on desktops everywhere.

Unsettling MOTD at my ISP.

According to the NPL leap second web page, there has never been a need to add more than one leap second per year, although the current scheme would permit two seconds to be added or subtracted per year.

In an old National Bureau of Standards (now NIST) publication, they mentioned the use of a rubber second to keep atomic time synchronized with GMT. This required a periodic redefinition of the duration of a second. It seems that this caused more problems than it solved, leading to the current system of a fixed TAI time scale, and a UTC time scale that is offset from TAI by an integral number of seconds, via leap seconds, to compensate for variations in the Earth's rotation.

Currently (7:49 Pacific time, New Years' eve) the National Physical Laboratory in Middlesex shows the current time as the 26th hour of December 31. This is the readout from the atomic clock at Greenwich. We're all doomed! :-)