Follow Slashdot stories on Twitter


Forgot your password?
DEAL: For $25 - Add A Second Phone Number To Your Smartphone for life! Use promo code SLASHDOT25. Also, Slashdot's Facebook page has a chat bot now. Message it for stories and more. Check out the new SourceForge HTML5 Internet speed test! ×

Comment Re:FP? (Score 4, Informative) 942

Australia completed this change in the 70’s very successfully without any of the problems you are claiming. Educating the public about the changeover and the new speeds is part of the process. Also, do you think that anyone from the UK who takes their car across to France or Ireland has trouble adapting to the speeds? All modern cars have km/h speeds indicated, even if only as a secondary scale.

Comment Re:FP? (Score 2) 942

Centimetres should never, ever be used in engineering. Millimetres are far more suitable for working with wood. They completely eliminate the need to work with any decimal points or fractions. When Australia converted to metric, the building industry very intelligently decided that mm is to be used exclusively and cm are not allowed.

Comment Re:Forcing strong passwords in the first place. (Score 1) 211

Actually, in my experience, most sites do allow good passwords. I have a little over 200 sites stored in my password manager, and of those, about 90% of them use long randomly generated passwords with letters, numbers and symbols. About 5% are still long, but imposed some restriction on either length or the use of symbols and the remaining 5% are crap due to really bad password restrictions limiting lengths to below 12 characters or less.

Comment Re:What is the issue? (Score 3, Informative) 442

The article said 600 MB/s, not "Mbps". There is a difference. The former is megabytes per second, the latter is megabits per second. And, yes, it does.

3840*2160 = 8294400 px/frame

Colour depth is 24 bits per pixel

And either 24, 25 or 30 frames per second, depening on whether it's native film rate, or adjusted for PAL or NTSC. In either case, the calculation is:

3840*2160 px/frame * 24 bit/px * 24 frame/s = 4,777,574,400 bits/s = 4.78 Gb/s or around 597.2 MB/s

It's obviously more for the higher frame rates.

Comment Re:begs the question... (Score 1) 177

The mass of such things has only been determined experimentally with a relatively significant margin of error. It's also not a definition that would lend itself to the development of practical realisations of the kilogram as what's called a transfer standard, nor a scale with which to test them.

It needs to be possible for weights to be produced, and then tested. The results from these tests would identify a given weight as being 1 kg plus or minus a measured error range. This then becomes a transfer standard, that can be used to calibrate other scales, and forms part of the traceability chain for certification. With a new definition, the current IPK would then become just another transfer standard along with all the other official copies.

Comment Re:Revised Standard (Score 1) 177

I commented about this elsewhere in the thread, but basically, the density of water is dependent on pressure and temprature. Pressure is dependent on force and area. Force is dependent on mass and acceleration, which creates a cycilical definition. Also, the level of precision and accuracy that water can be measured is not high enough.

Comment Re:Why isn't there a precise atomic standard? (Score 1) 177

If that were ever found to be the case, then we could just redefine the second to something that is even more accurate than its current definition to resolve the problem. The new definition would define a new value that is within an acceptably small margin of error (probably on the order of a few femtoseconds or less), such that the new definition doesn't significantly alter the definition of any other units linked with it, at least within any measurable precision.

Comment Re:The meter is based on the speed of light (Score 2) 177

The density of water is dependent on temperature and pressure. Pressure is defined as a unit of force per unit area (Newtons per square metre). Force is subsequently defined in terms of mass times acceleration (1 N = 1 kg * 1 m/s^2). Congratulations, you have just created a definition of mass that is dependent on itself. Also, the ability to purify water and measure its volume to a high enough accuracy and precision is extremely difficult.

Comment Re:You are worng (Score 1) 177

Wow, you fail. If the US had some miraculous metal that could maintain a very constant mass, with greater accuracy than the IPK, then such a thing could also be used for the kilogram. But you are wrong, and they don't. Any artifacts the US does use for mass calibration, which includes at least their official copy of the kilogram, are also subject to the same kind of fluctation in mass that the international prototype kilogram is for many of the same reasons, if not more because it's handled far more frequently than the IPK is.

Comment Re:begs the question... (Score 5, Informative) 177

That was the original definition, but it's not precise enough. It's extremely difficult to get water with an exact isotopic composition. VSMOW is used, but even that is not reliably reproducible to the necessary level of precision.

Also, the density of water is very much related to the temperature and air pressure. Pressure is measured as a unit of force per unit area. Typically, Newtons per squre metre (the Pascal unit). Force, is then in turn defined as a unit of mass times acceleration, with the Newton being 1 kg * 1 ms-2, which obviously results in a cyclically dependent definition, because it would be defined as 1 kg of pure water at a specific temperature and pressure measured in:

Pa = N/m^2 = kg/m*s^2

To get around this problem, you would need to define the Newton in terms of its relationship to other units, ultimately ending up linked to a fundamental constant of nature. The Watt balance approach is trying to do this, by linking the definition with the Ampere. That would reverse the relationship of the Ampere, which is currently defined in relation to the kilogram.

That would then gives a direct way to link those units with the kilogram, and there is no need to precisely measure 1 cubic decimetre of water. You just develop an extremely precise scale that can measure any test mass very precisely and accurately based on the new definition. The difficulty is actually putting that into practice and eliminating as much measurement error as possible. NIST and other laboratories around the world are trying. The problem is, the margin of error in the measurements are still higher than desired.

Comment Re:Good luck with that. (Score 1) 1387

With a well managed, rapid changeover, you too would get used to the new system in no time. A lot of people over estimate the difficulty in switching because they don't understand how a well managed changeover works.

The best way to switch is to do it quickly. Eliminate as many non-metric units as possible. Get rulers, scales, and whatever else that measure exclusively in metric, and start actually using it.

The most basic things you could do in your own home are to set your kitchen and bathroom scales to metric, get rulers and/or tape measures that are labelled in mm-only. Learn your own height in cm. Learn the size of things around your home in metres (such as the height of a door, the length of your table, the distance from your couch to your TV, etc.) Get thermometers that are labelled in Celsius (or cover up any Fahrenheit labels) and use websites for weather forecast that let you set your preferences to Celsius and either km/h or m/s for wind speed. Find recipes that specify all ingredients primarily in grams or millilitres (A lot of UK recipes do this) and avoid recipes that specify measurements primarily in cups and spoons.

If you were to consciously make the decision to switch your own life to metric (which I would strongly recommend), and did so by removing any and all temptation to revert to the old system, then you would adjust in no time.

Many other people your age and older have done it in many other countries. There's nothing preventing you from doing it too, except your own willpower.

Comment Re:Trouble with that... (Score 1) 1387

There are many reasons to convert that aren't simply because everyone else is.

The US is effectively in a state of operating with dual measurement systems, and that is costing your economy significantly. Various industries need to keep and maintain two different sets of tools with different measurements, many industries use a confusing mix of both units. e.g. The electronics industry is a big mess, with internationally acquired components being specified in metric, while PCB design and manufaction in the US is done in imperial. Internationally, everything is done in metric.

Your roads are designed in Ramsden's chain (100 US survey feet), with long distance measurements being done with GPS in metres and then converted.

NASA has fucked up so many times, by living in a hybrid world of both systems, rather than actually properly committing to change.

Your continued use of non-metric units in the health industry risks lives due to doing calculations with the wrong units. e.g. calculating how much medication to prescribe and accidentally using lbs instead of kg. Or using non-standard symbols for metric units, such as MG for milligram (which should be mg) and MCG for microgram,which should be ug (slashdot won't let me enter the proper micro sign) More info on these problems here.

Ultimately, this hybrid system costs your economy more because you cannot effectively work the the same set of tools that everyone else can. It affects your education system because kids must learn two systems, and yet when learning metric, have very little reinforcement in the home due to many consumer products being labelled in USC or both systems, with comparitively few labelled in exclusively metric. I think wine bottles are one of the few products that aren't labelled in both systems.

Comment Re:Trouble with that... (Score 1) 1387

Things like road signs are also up to the individual states, and given that most of them are bankrupt, it would be hard to convince them to add that to their budget.

"The Congress shall have Power To ... fix the Standard of Weights and Measures" - US Constitution.

That gives the federal government the power to state what is and is not a legal unit of measure. Make miles, feet and yards illegal for trade, and set a proper deadline for conversion, and the states will have to comply. As a bonus, it would also create thousands of jobs around the country, with jobs including manufacturing road signs, printing temporary replacement signs to be used for a rapid changeover, and employing workers to actually go out and install the new signs.

With proper planning and management, the whole thing could be organised and completed within 1 to 2 years, with an effective rapid changeover date around the end of that period, and with ongoing maintenance taking care of the removal of old signs with new permanent signs.

Slashdot Top Deals

Nothing motivates a man more than to see his boss put in an honest day's work.