Re: The amount of times...
Hmmm, 100C is where the vapor pressure of pure water is the standard atmospheric pressure at sea level. At 1 to 1.5km of elevation, the drop in temperature at where the vapor pressure of water is equal to the ambient pressure is enough to require adjustments to recipes when baking. The more natural point for 0C would be the triple point in water. Fahrenheit's scale was 0F being the coldest achievable temperature with water ice and NaCl, with 100F being core body temperature. A real SI scale fr temperature would be eV...

For doing thermodynamic calculations, the appropriate scales are Kelvin and Rankine, and there really isn't much difference in usability between K and R as all sorts of conversions need to be done to get answers in Joules or MWHr. Another "fun" problem is dealing with speed involves Joules being watt-seconds, while vehicle speeds are usually given in statute miles, nautical miles or kilometers per hour. A fun factoid is that 1 pound of force at one statute mile per hour is equal to 2.0W (1.99W is a closer approximation).

As for feet, a fair approximation is that light travels 1 ft/nsec, too bad the foot wasn't ~1.6% shorter as a light nano-second would be the ultimate SI unit of length. The current definition of an inch, 25.4mm, was chosen in the 1920's to allow machine tools to handle inches by having a 127 tooth gear instead of a 100 tooth gear.

FWIW, Jefferson wanted to base his unit of length on a "second's" rod, i.e. e pendulum whose length would have exactly one second period when measured at seal level and 45º latitude.

Don't get me started on kilograms of thrust.

Friday 27th January 2023 06:22 GMT
IvyKing
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Re: The amount of times...
From somewhere in the later half of the 19th century to ~1920, the US inch was defined as 39.37 inches equals 1m. According a ca 1920 issue of Railway Mechanical Engineer, the machine tool industry was making a push to defining the inch 25.4mm so that by using a 127 tooth gear to replace a 100 tooth gear a lathe could be set up to produce metric and imperial threads.

One problem with converting the US to pure metric is that almost all land titles use feet, not meters. The US legal definition of a foot was 1/66 of a chain, a mile was 80 chains (66x80=5280), a section of land under the Northwest Ordnance of 1787 (passed under the Articles of Confederation, NOT the Constitution), which was 6400 square chains and the acre being 10 square chains (640 acres per square mile). The surveys for the Townships (36 sections) didn't really start until ca 1796, so if the arrival of the metric standards had not been delayed by the storm and the English, the US might have re-written the 1787 law to use metric measurements.

Another problem with the US converting to metric was Herbert Hoover's success as Secretary of Commerce in setting national standards for pipes and other hardware.

One final note about metric versus imperial is that a nautical mile is defined as 1 minute of longitude at the equator, so works well with the degrees, minutes and seconds customarily used for angles. Metric navigation would favor a decimal system for expressing angles, i.e. the gradians.

doublelayerSilver badge
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Re: The amount of times...
"Fahrenheit's scale was 0F being the coldest achievable temperature with water ice and NaCl, with 100F being core body temperature."

Wrong on both counts. On Fahrenheit's original scale, 0 was the freezing point of a solution of ammonium chloride (NH4Cl), not table salt (NaCl). As neither compound is used directly on roads, the point at which it is not useful depends on which specific salt is being used in the area, and more importantly on where the compound has been applied and whether it has been moved or not. The temperature of the human body was not 100. It was 96. Of course, neither value is considered average for body temperature (and body temperature is incredibly variable in any case, whereas boiling points of things at a specific fixed pressure is stable). This is because the modern scale abandoned both limits by instead fixing 32 and 212 as the values for water freezing and boiling, moving both of the original bounds slightly and making use of the original scale inaccurate to modern users.

Wednesday 25th January 2023 01:55 GMT
-tim
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Coat
Re: The amount of times...
In 1700 it was much easier for a scientist to calibrate a home made thermometer using ammonium chloride cooling bath and a docile dog. The temperature of boiling water required a barometer at higher altitudes and calibration tables. The human armpit temperature of about 96 allows hand drawn hash marks in repeated halves. Many very early Fahrenheit thermometer are often marked every 3 degrees.

Monday 23rd January 2023 15:59 GMT
Michael Wojcik
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Re: The amount of times...
More importantly, for Fahrenheit the reference temperatures aren't 0 and 212; they're 32 and 96. 96 minus 32 is 64. And 32 and 64 are ... stay with me here ... powers of 2.

Fahrenheit based his scale on powers of 2 so that thermometers could be graduated by successive bisection (and then reflected to extrapolate outside that range, on the assumption that the mechanism was sufficiently linear within the desired range). That's an actual engineering reason, unlike "duh humans like powers of 10". There really isn't much reason to favor Celsius.

Kelvin, of course, is the one that matters. (Yes, Rankine works too, but for some SI operations Kelvin is more convenient.)

Celsius is today as much flavor-of-the-month as Fahrenheit is. The original justifications for them are no longer relevant; they're just a matter of taste.

Re: Hooray for Avoirdupois and pounds, shillings and pence
Auvoirdepois has nothing to do with pounds, shillings and pence. Precious metals are measure using the Troy system that has 20 ounces to the pound. That is why a pound of gold weighs more than a pound of feathers. 1GBP was originally worth a pound of gold hence 20 shillings to the pound.

In 1793, French scientist Joseph Dombey sailed for the newly formed United States at the request of Thomas Jefferson carrying two objects that could have changed America. He never made it, and now the US is stuck with a retro version of measurement that is unique in the modern world.

The first, a metal cylinder, was exactly one kilogram in mass. The second was a copper rod the length of a newly proposed distance measurement, the meter.

Jefferson was keen on the rationality of the metric system in the US and an avid Francophile. But Dombey's ship was blown off course, captured by English privateers (pirates with government sanction), and the scientist died on the island of Montserrat while waiting to be ransomed.

And so America is one of a handful of countries that maintains its own unique forms of weights and measures. //

When the UK settled in the Americas they brought with them a bastardized version of weights, measures and currencies. A Scottish pint, for example, was almost triple the size of an English equivalent until 1824, which speaks volumes about the drinking culture north of the border.

British measurements were initially standardized in the UK's colonies, but it was a curious system, taking in Roman, Frankish, and frankly bizarre additions. Until 1971, in the UK a pound consisted of 240 pence, with 12 pence to the shilling and 20 shillings to the pound. //

The French government felt that the newly formed nation wasn't being supportive enough in helping Gallic forces fight the British in the largely European War of the First Coalition. In something of a hissy fit, the French government declined to invite representatives from the US to the international gathering at Paris in 1798-99 that set the initial standards for the metric system.

Jefferson's plans were kicked into committee and while a form of standardization based on pounds and ounces was approved by the House, the Senate declined to rule on the matter.

Servers on exaroton don't have a fixed monthly price. You are only charged for the time you actually use your server.

To pay for services on exaroton, you use credits, each of which is worth €0.01. After creating your account, you get 5 credits for free to test our service. //

Running a server on exaroton costs 1 credit per GB of RAM per hour. For example, if you select 4 gigabytes of RAM for your server and run it for 1 hour, you would pay 4 credits. You can choose how much RAM (2 GB to 16 GB) you want to assign to your server on the Options page. //

To save credits, it is recommended only to run your server when somebody is playing on it. To achieve this, exaroton provides you with an AutoStop feature to automatically shut down your server when it has been empty for a while and an AutoStart feature to start your server automatically as soon as somebody tries to join.

Both features can be enabled for free on the Options page. We will only charge you for the time your server is actually running.

Try Deepl:
Reindeer length is an old unit of measurement of length used when moving reindeer. Reindeer length is the distance a reindeer can travel between (reindeer) urination breaks. Reindeer cannot urinate while running, and running too long can cause them to become paralysed. The maximum distance a reindeer can run is up to 7.5 kilometres.

Re: Try Deepl:
Nobody said they couldn't urinate while flying. That's why I stay inside on Christmas Eve.

Mostly you don't see a difference, unless you are using set -u:

/home/user1> var=""
/home/user1> echo $var

/home/user1> set -u
/home/user1> echo $var

/home/user1> unset var
/home/user1> echo $var
-bash: var: unbound variable

So really, it depends on how you are going to test the variable.

I will add that my preferred way of testing if it is set is:

[[ -n $var ]]  # True if the length of $var is non-zero

or

[[ -z $var ]]  # True if zero length

rrsync is designed to be used as a forced command for a particular key, so it should be exactly what you want.

A forced command is set up using the command option for a key in an authorized keys file and is then always run whenever this key is used for authentication, no matter what command the client requested. But it has access to the requested command so it can for example implement a validated, restricted version of it and that's what rrsync does.

You use it like this:

command="/path/to/rrsync -wo /allowed/directory/",restrict,from="a.b.c.d" ecdsa-sha2-nistp521 AAAAE...

Access for this key is limited to rsync to the /allowed/directory/ only. The -wo (write only) option means that rsync will be only allowed to send to the remote machine, -ro would only allow reading from the remote system, giving no option would allow transfer in both directions.

On the local side when you give arguments to rsync you must give the remote path relative to the allowed directory, so on A you would do eg.rsync -options /local/path root@B: and not rsync -options /local/path root@B:/allowed/directory/.

See also https://serverfault.com/a/915842/117645