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.
Riffle seven times and you’ll have a sufficiently random ordering of cards, an ordering that has likely never existed before. In other words, it’s unlikely you’ll ever shuffle two decks the same. //
...what if instead of a standard riffle using a deck roughly split in half, you were to only riffle 1 card at a time?
That is, using a standard deck of 52 cards, in one hand hold 51 cards and in the other hold the remaining single card. Now riffle these together. This is equivalent to taking one card and placing it at random inside of the deck.
So here’s the question:
How many single riffles do you have to do in order to have a completely shuffled deck? //
On average, 236 single card riffles will randomly shuffle a deck of cards. //
Equations are great, but let’s visualize this! Below is the same ordered deck of cards from before, except the K♦ has been highlighted red so we can follow its journey to the top of the deck.
Click the Riffle button to move the top card somewhere else in the deck randomly.
On its initial publication in 1998, John R. Lott’s More Guns, Less Crime drew both lavish praise and heated criticism. More than a decade later, it continues to play a key role in ongoing arguments over gun-control laws: despite all the attacks by gun-control advocates, no one has ever been able to refute Lott’s simple, startling conclusion that more guns mean less crime. Relying on the most rigorously comprehensive data analysis ever conducted on crime statistics and right-to-carry laws, the book directly challenges common perceptions about the relationship of guns, crime, and violence. For this third edition, Lott draws on an additional ten years of data—including provocative analysis of the effects of gun bans in Chicago and Washington, D.C—that brings the book fully up to date and further bolsters its central contention.
It’s become virtually impossible to find reliable data or polling on gun violence these days. A new Kaiser Family Foundation report being shared by virtually every major media outlet this week offers us a good example of why. The headlines report that “1 in 5 adults” in the United States claim that a “family member” has been “killed” by a gun. And, let’s just say, that’s a highly dubious claim.
There are 333 million people living in the United States, and somewhere around 259 million of them are over the age of 18. Twenty percent of those adults equals nearly 52 million people. There were more than 40,000 gun deaths in 2022, and around 20,000 of them were homicides — a slight dip from a Covid-year historic high that followed decades of lows. So, according to Kaiser’s polling, every victim of gun violence in the past few years had hundreds, if not thousands, of “family members.”
Now, to be fair, we can’t really run the numbers because Kaiser doesn’t define its terms or parameters. For example, what constitutes a “family member”? Is your second cousin a family member? Because if so, that creates quite the nexus of people. What about your stepbrother’s second cousin? Or how about your uncle who died in Iraq? Or how about that grandfather you never met who committed suicide in 1968? Kaiser could have asked people about their “immediate” relatives. The opacity is the point.
Then again, you can always spot a misleading firearms study by checking if the authors conflate suicides and murders. Kaiser does. //
What Kaiser doesn’t mention in its press-friendly “key findings” — and no media piece I’ve read mentions — is that 82 percent of those polled feel “very” or “somewhat safe” from gun violence in their own neighborhoods. Only 18 percent of Americans say they worry about gun violence on a daily or almost daily basis, while 43 percent say they worry about it “rarely” or “never.” So, you’re telling me, half of American adults have personally experienced gun violence themselves or toward someone in their family, but less than 20 percent worry about it often?
We report a retrospective case series of exposures to iocane powder, a deadly, odorless, tasteless, and absolutely fictional poison [1]. A 10-year review of an imaginary Sicilian Poison Center database revealed 32 exposures, coincidentally all ingestions from wine goblets. There were 29 (90.6 %) patients with no clinical effects, 2 (6.3 %) with minor effects, 1 (3.1 %) with a moderate effect and 0 with major effects. No deaths occurred and no patient suffered permanent sequelae. These data show that iocane exposure is not universally fatal, as previously thought. Given the apparent relative safety, with less than 10 % of patients experiencing clinical effects, poison centers may choose to allow asymptomatic exposed patients to be observed at home.
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