"(...) he had the idea for the update when he saw media reports using unsanctioned prefixes for data storage such as brontobytes and hellabytes. (...)" and "The only letters that were not used for other units or other symbols were R and Q"
So it seems the new prefixes are partly initiated by the exponential computer storage needs rather than scientific needs. So they might need to move again soon. However the SI has exhausted the available stock of letters. Maybe Greek letters next time like micro for 10^-6.
Anyway does it really matter for IT people? I have seen so many people mixing up bit and byte, milli- and mega- as well. There are countless usages of mb all over the Internet to express MB.
The only use cases I have seen for units larger than 'petabyte' are those representing the maximum allowed file sizes for ZFS, Btrfs and such. I also don't see a point in inventing more prefixes so that statisticians don't have to use scientific notation for large numbers. What use is that? How many people know how much a yottabyte is? If they need to Google the answer, that defeats the point.
1e12 terabytes seems easier to digest than 1 whatever-the-hell-,-I-don't-know-what-this-unit-is-meant-to-represent-byte. Not to mention, easier to read.
Hmm, why would you mix 1e12 terabytes instead of saying 1e24 bytes? Why do we talk about 200k USD salaries instead of 2e5 USD? Or why isn't a US postage stamp marked as 6e-1 USD?
Also: in the past 25 years, "tera-scale" (TB and TFLOP) went from a prognostication about future high-performance computing into something you find in affordable consumer products. When campus computing centers are now deploying hundreds of petabytes, it seems myopic to think the PB threshold is anything but a signpost flying by the window...
It's kinda funny that you mention it. If we say to someone '99 hundred', they'd immediately understand it as 9,900. If we say 'hundred hundred', it's an immediate math problem trying to figure out how many zeros and what it's called. At least, that's how I'd react.
> If we say to someone '99 hundred', they'd immediately understand it as 9,900.
That's definitely untrue. In my native language we never mix tens and hundreds, and it always takes me a moment to parse that "thirteen hundred" means one thousand and three hundred.
Ah, I should have specified in the US. It's more common to say numbers between 100 and 10k as hundreds, unless it's exactly on a thousand. I think most people would say nineteen hundred, or 21 hundred for 1900 and 2100, but nobody would say 20 hundred for 2000(except for military time).
SI prefixes could originally be combined like that: it was perfectly fine to say one hectokilometre. Such usage is now deprecated, though. You'd have to say 0.1 megametre instead.
Uppercase MB is megabytes, lowercase mb is millibars. Both can go through a series of tubes, but millibars are also useful in dump trucks, to make the wheels go round and round.
The prefixes ronna and quetta represent 10^27 and 10^30, and ronto and quecto signify 10^−27 and 10^−30. Earth weighs around one ronnagram, and an electron’s mass is about one quectogram.
This is the first update to the prefix system since 1991, when the organization added zetta (10^21), zepto (10^−21), yotta (10^24) and yocto (10^−24).
The character sequence 10^27 is of equal length as 'ronna' and much cleaner. The only thing left was a smart short way to speak it without losing the semantics.
How about 10^17 == "tenset", 10^27 == "venset", ...
Inspired by French vingt, from Old French vint, from Latin vīgintī.
Since the length of words (should) correspond to the frequency of usage, longer variants would be ok if not preferable too:
Is there a convention for prefixes for 10^n where abs(n) > 3 and n % 3 != 0? It seems strange to me that we would have prefixes for 10^+/-1 and 10^+/-2 but not for any larger values.
Are you American by chance? Because I can assure you that centimetres are everywhere here and both hectolitres and centilitres are fairly common, not to talk about decibel.
decibel is a bit of a special case, as that is essentially the only form anyone uses (I operate in a world that is decibel-heavy and I can't remember ever having seen a bel in the wild).
It's not so strange - a lot of our natural experience of the universe is within 3 orders of magnitude of the base units we use. Those are very commonly referenced and as such have common prefixes.
> a lot of our natural experience of the universe is within 3 orders of magnitude of the base units we use.
That may be in large part because of the unit prefixes we use. That is we think of these things in 3 orders of magnitudes because our unit prefixes come in three orders of magnitude but not the other way around. I think a much likelier explanation is the fact that many European languages (most importantly French and English) stop naming each decimal order after a thousand. If there was a word for ten-thousand—say fiorthom—but not a hundred-thousand (ten-fiorthom), surely these prefixes would map be multiples of 10⁴ as well.
The hectopascal is the most common unit for atmospheric pressure. It replaced the equivalent millibar to match SI units. Standard atmospheric pressure at sea level is 1013 hPa.
Hectolitres are commonly used in the food and drink industry. For example wineries and breweries typically measure their production in hectolitres.
Not exactly hecto but land, especially farm land is often measured in hectares. It is a non-SI metric unit equivalent to the square hectometer or 10000 square meters. We most likely kept the name because "hectare" sounds better than "square hectometer". As expected, 1 hectare is worth 100 ares, but ares and its other multiples are much less used than hectares.
India commonly uses Lakh for 10^5 1,00,000 and Crore for 10^7 1,00,00,000. After that, there's Arab at 10^9, Kharab at 10^11, Neel at 10^13, and Padma 10^15, but as a US person, I've never seen those used, although I've seen Lakh and Crore. Sometimes lakh crore shows up, which is 10^12 or a (short) trillion, but sometimes trillion is used for that in documents otherwise using lakhs and crores and not billions or millions.
(I'm Indian.) Yes, India groups the first three digits and then subsequent groups are two digits, eg 12,34,56,789. So instead of hundred thousand it's lakh, and instead of hundred lakhs it's crore. We never learned any numbers above crore in school. I remember hearing about arab from other kids but never saw it used, and I never heard about the others you mentioned.
In Japan and China you use groups of 10,000, so there's 万 (1e4), the largest bill (10,000 yen); 億 (1e8, 100 million), the approximate population of Japan and a convenient unit for housing prices in yen; and 兆 (1e12, 1 trillion), which is used for eg really expensive infra projects like new bullet trains.
On paper, there are much larger units too, but they are never used.
Not while using the standard Greek alphabet. There is no letter for the sound /h/; it is represented as a diacritic mark applied to the first letter of a word.
(For completeness, aspiration is not strictly restricted to the beginning of a word in classical-to-Byzantine Greek. It might be represented in one of three ways:
- At the beginning of a word, according to Byzantine convention, it is represented by an aspiration mark, discussed above. This can only occur if the word begins with a vowel, or with R. (All words beginning with R are aspirated.)
- Following a /p/, /t/, or /k/ sound, aspiration is represented by mutating the letter into an aspirated form. Unaspirated π becomes aspirated φ, τ becomes θ, κ becomes χ. By the time we're talking about Byzantine Greek, the "aspirated" letters have mostly mutated into other sounds. But for ancient Ancient Greek, they are aspirated forms.
- Doubled Rs have something special going on with them, and the Byzantines use a diacritic mark on the second R even though, obviously, it cannot occur at the beginning of a word. Again there is no contrast between "aspirated" and "unaspirated" double R; the aspiration is mandatory.
As you move into earlier stages of Greek, you lose the standardization of the alphabet; there are plenty of Greek inscriptions where the sound is represented by the glyph H.)
Yes and the circumference of the earth is about 40 million meters. This is because a meter was originally supposed to be 1/10E6 the distance from the equator to the north pole through Paris.
Earth’s circumference around the poles is now given as 40,007.863 km [1]. So when the French Academy of Sciences defined the metre in the 1790s [2] the distance they measured from equator to North Pole was off by less than 2 km.
I have read that the atronomers at the time actually knew that they were a bit off due to a mistake that was done by one of them.
They spent several years making lots of smaller measurements that were added up.
Each measurement was done twice to ensure correctness. One of the distances had two conflicting measurements, but due to a war, they could not return to make a third measurement and had to just choose one of them (the wrong one).
They chose not to tell anyone because they feared politicians would use it to discredit the metric system.
Nitpick: 1/10⁷, not 1/10⁶. They picked the power of ten that gave a reasonably-sized unit of length.
They also made things complex by then picking a unit of mass that’s inconsistent with that: a gram isn’t the mass of 1m³ of water, but of 1/10⁶ m³ of water (a cubic meter is 10³ liters, and a liter of water weighs 10³ grams)
The gram is the easiest to save by working backwards from Avogadro's number.
Avogadro's number is close to 24!, so we could redefine our mass unit as exactly 24! hydrogen atoms (or 4!!) and that comes out to within about 3% of a gram while being significantly easier to communicate to an extraterrestrial civilization.
Picking 1/10^9 would also have had the advantage of making the distance from the pole to the equator ~1 gigacentimeter.
Exploring a bit, picking 4 times that, as an estimate of the circumference, would give us a basic length unit of 4 cm (a pretty reasonable unit—bit over an inch and a half, fits right in with the variety of Chinese cun standards, for example). Then our immediate volume unit is 64 mL, which seems kind of small (on the scale of 2 floces), but ten of them make a decent "pint", so I think it can work—it's ~13% bigger than an imperial pint instead of ~12% smaller. the corresponding mass unit, at ~64 g, which again seems a bit small but manages to line up an average person's weight right around 1 kilo.
For me, it's: Earth is a blue marble - in "Mega-view" (Mm zoomed to mm) - with a diameter of a baker's dozen Megameters. The volume of a ball is one half of its enclosing box, so that's ~(1E7)^3 or 1E21 m^3. Earth is rock (3 Mg/m^3) and iron (8 Mg/m^3) and averages 5 Mg/m^3. Or just bracket it - water,lead,gold is ~ 1,10,20 Mg/m^3). Giving an Earth mass of 5E24 kg. Actual value 6E24 kg. Brackets of water and lead give 1E24 to 11E24 kg.
> a great way of drilling in these tidbits
For me it's: Arm-sized, hand-sized, fingernail-sized, and "tiny"-sized, are 1000, 100, 10, and 1 mm. Zooming these by 1000^n gives scale-model "views". Mega-view with planet balls, kilo-view with cities in your palm, meter-view with buildings in hand, micro-view with red blood cell M&M's (yum), nano-view with virus balls (chewy shell, stringy inside), pico-view with H2O bumpy basketballs, femto-view with nuclei marbles. It's easier to remember how big things are, once they're toy-sized, and you've handled and played with them.
Just something I crafted years back. Resulting videos didn't seem to user test well. I was set to dust it off, doing rapid iterative development over gorilla street usability testing... in Spring 2020. Ah well.
And here in US, we are stuck with imperial units like it was 1800s: oz, pounds, inches, feet, miles, etc for all common usage. When a foreigner visits here, the first thing they realize is how US has truly siloed itself from the rest of the world.
A couple of decades and several jobs ago I wrote some file transfer code that displayed human readable sizes, and as a joke to myself, I included prefixes up to yottabytes. Careful readers of the code should have flagged this as impossible because anything above exa- is impossible using 64 bits, but it got thru review and as far as I know the code lives on to this day. I'm hoping someone adds these new prefixes.
“The SI has been adopted as the official system of weights and measures by all nations in the world except for Myanmar, Liberia, and the United States.”
Well, isn't that by definition true for any system of measurements? I mean, as long as we're talking about a simple straight-line distance in some real-dimensional space, it's going to be possible to measure that distance in meters (or yards, or whatever). Yes I know about fractal lengths, coastlines and so on.
I think the point is that the US customary units are typically used in a very different way, with fractions being way more important than in metric. See the image in this [1] article that talks about drill sizes for DIY use, for instance. You guys go like "oh no the 5/16:ths hole is too small, I'll step up to 19/64ths that should do it". Over here in metric-world we go more like "oh no the 7.9 mm drill was too small, I'll step up to 8 mm".
Again, the fact that it's easy to convert the 5/16:ths to 7.9375 mm is not the point, the point is how the decimal/metric units are used in practice.
> Well, isn't that by definition true for any system of measurements? I mean, as long as we're talking about a simple straight-line distance in some real-dimensional space, it's going to be possible to measure that distance in meters (or yards, or whatever). Yes I know about fractal lengths, coastlines and so on.
The US yard is exactly 0.9144m such a short decimal expansion is highly unlikely when selecting two random units of measurements. It is short because we defined the modern yard in terms of meters, selecting a short decimal expansion that was still "close enough" to the old definition to allow tooling to remain the same.
No. It's true because 1 inch is explicitly defined by the governing body as 2.54 cm, whereas one meter is defined as "the length of the path travelled by light in a vacuum in 1/299792458 of a second". https://en.wikipedia.org/wiki/Metre
The units of the metric system are defined by physical properties that appear to be constant throughout the universe.
The units of the US customary system are defined as some exact number of equivalent metric units.
The inch wasn't converted to a derived metric unit in the US until 1959. This creates an issue for precision machinery manufactured before the redefinition because the slight difference is enough to matter where allowed to accumulate.
This is meaningless. Everything is metric and nonmetric at the same time by this definition since you can always find a linear equation which let's you convert between the systems.
And the UK, unless for some reason their official speed limits and such aren't actually, you know, official.
As a practical matter, we use metric for many things in the US. The fact that we do not force everyone to change their customary units to metric really seems to irk some folks, but mostly outside the US.
Uk is metric, but we do use a mix. Speed limits are still in mph, and we rarely if ever use kilometres for distances. Height is in ft and inches, and your own weight is in stones/pounds. All other weights are in grams and kg, except for some larger ones (industrial/shipping) which are in tonnes. Pints are used only for… pints, everything else is in ml.
And, the best, is “football pitches” which is often used by the news to describe large (but not too large) lengths.
My favourite bit of nonsense is signs for distance for walkers. Distances are usually in miles or fractions of miles but for indicating things really close by (e.g. toilets round the corner) we switch to metres.
I've found that it's becoming increasingly common to use metric for height and weight also - particularly with younger people etc.
I think we'll soon be left with the only remaining imperial bits being speed, long distances, and pints of beer - none of which seem likely to go away any time soon
For pints (only really used for beer and milk), we still use an imperial pint but it's officially specified in millilitres (568ml) and this will always be printed on packaging.
weird question for anyone with the relevant knowledge, would 25 ronna-Reagans in one place behave differently than our sun? I know that mass would be mostly oxygen, but at that scale does it matter?
Are you asking in terms of gravitation or as a star?
By mass, the sun is 71% Hydrogen and 27.1% Helium, the last 1.9% or so being heavier elements (much of that being oxygen.
I’m no expert, but I suspect a mass of 25 ronna-Reagans would not make a very good star. I imagine it might collapse into a dense Oxygen and Carbon rich sphere, and in that environment various chemical reactions might turn it into some other kind of material.
Upping the mass to the sun size would cause some interesting additional wrinkles because now we're talking about being large enough to have "problems" with the pressures in the middle being sufficient to start causing atoms to squish together, but it would take an astronomer to be clear on what happens next. My gut and layman's understanding says you might get a pretty big boom in a couple hundred thousand years or so, because you'd basically be building a sun that would be fairly far along its fuel consumption cycle.
Raegan was a complete walking disgrace. But the media was very kind to him, if you don't investigate carefully what he was doing you'll believe that he was a great president. The only explanation I see is that he was fantastic for the war industry and gave everything the very rich were expecting in terms of fiscal policy.
Still, I'm probably the 1% of 1% of Americans who uses Celsius in daily life, except where I cannot (my car won't let me do hybrid miles and Celsius, ugh).
> U.S. customary units have been defined in terms of metric units since the 19th century, and the SI has been the "preferred system of weights and measures for United States trade and commerce" since 1975 according to United States law.[1]
Is anyone seriously using prefixes above Giga, besides for counting bytes or boasting numbers in popular science articles?
In physics, in practice you either state the number in exponential notation and don't care abut it or for brevity introduce a more appropriate unit: barns (10⁻²⁸ m²) and electronvolts (10⁻¹⁹ J) in nuclear physics or solar mass (~10³⁰ kg) in astrophysics, etc.
Electricity production for a country is reasonable measured in TWh, and I think I've seen this in newspapers discussing energy/gas in Europe.
But from Wikipedia:
> In the United Kingdom ... Demand for electricity in 2014 was 34.42 GW on average (301.7 TWh over the year) coming from a total electricity generation of 335.0 TWh.
We aren't there yet for power:
> The synchronous grid of Continental Europe is the largest synchronous electrical grid (by connected power) in the world. ... In 2009, 667 GW of production capacity was connected to the grid
Boasting in popular science articles with large prefixes is hardly better communication compared to scientific notation. If the prefixes aren't commonly used (anything above tera/peta really isn't), then the majority of people have no frame of reference for what it is any more than it being "a big number".
No! The Earth does not have weight! It has mass. Weight is a force. It is a function of gravitational pull between two masses.
If you want to talk about force you have to use Newtown's Law of Universal Gravitation:
F = (G * m1 * m2) / r**2
You could speak in terms of gravitational pull between the earth and the moon or any other object in space, and that's about it.
I can't see how the concept of weight makes any sense when it comes to a planet. At all. Think of a hypothetical object in the middle of space with nothing whatsoever around it for millions of light years. No weight. Mass, of course.
You can't just use earth's 9.8 m/s*2 to convert from Kg to Newtons...that makes no sense at all in the frame of reference of any planet, even earth.
This isn't pedantic at all. Try to take a physic test anywhere and confuse these concepts, units of mass and force and see how well you do.
It is very important to distinguish the 2 physical quantities whose standard names are now "force" and "mass", but it is debatable whether it was good choice to arbitrarily assign to the word "weight" the meaning of a force and to establish the new word "mass" (new with this meaning) for what is now called "mass".
The word "weight" and its equivalents in other European languages, e.g. "poids", "pondo" etc., have been used for thousands of years principally to name the quantities measured by weighing with a balance, which are masses, not forces, and only seldom and mostly metaphorically and non-quantitatively to refer to a force. By etymology, such words derive in one way or another from the operation of using a weighing balance, e.g. "pound" means "hanging", from hanging objects on the weighing scales.
The word "mass" has been used for thousands of years only with a meaning that had nothing to do with a measurable quantity, but only to name some amorphous piece of some material, such as dough, clay, soil, rubble.
A wiser choice would have been to name as "weight" what is now named "mass" and to use a name such as "force of gravity" for what is now named "weight".
Such a terminology would have kept the continuity with the traditional meanings of the words and would not have offered opportunities for the majority of the people, who even today continue to use those traditional meanings in colloquial language, to be corrected by those who have made an arbitrary choice to assign new meanings to old words.
Unfortunately there exists a very large number of scientific or technical terms whose meaning has been changed some time during the last few centuries, sometimes intentionally, due to questionable decisions, but in many times due to various errors or misunderstandings.
Even when such names reflect very serious errors of those who have coined them, their meaning can no longer be changed, as too much new literature has accumulated, which uses the new meanings.
Can someone ELI5 how you “weigh” the earth? Isn’t weight based off gravity? And gravity is relative to the mass of the object you are on, for example we say you would weigh less on the moon and more on Jupiter. So how exactly to you weigh a planet, and why would that even be useful? Do you assume some theoretical force and hypothetically place the earth on a scale and apply that force? When talking about planets isn’t mass a better way to measure and classify rather than weight?
My lab at the time slipped hella- into a few conference presentations here and there. We had to back our university. I always remember it getting a few chuckles.
The strange thing is the symmetry. Why these prefixes cover multipliers from 10^-30 to 10^30? Why not 10^-20 to 10^40? Where the symmetry comes from?
Is it just people think that symmetry is a good thing, and for example they added 10^-30 despite the lack of demand? Or there is some deeper reason? Or it is more like one of those coincidences?
I think it's because we can scan it easily. Groups of 4 or more can confuse the eye: when looking at 5 things, you sometimes have to take a moment to realize it's 5 not 4 (and, to a lesser extent, the same is true of 4).
groups of 3 have first, middle, last - crucially _one_ middle digit, not 2+, which makes for quick comprehension.
The problem with languages that use 10,000 is they still use commas at 1,000, so you get a very awkward offset that then requires a mental translation between numeric and verbal representations.
Sure if you grow up with it, you have that translation basically hard-coded but it’s still not ideal.
Which is stupid. It is annoyingly frequent that the common scale in the table is stated as powers of 1,000, not 10,000, but the scale itself is written verbally (e.g. "단위: 십억원" billion wons, much like "ten thousand dollars").
Is it? If 1 lakh is 1,00,000 and 1 crore is 1,00,00,000, wouldn't the consistent grouping for 1 lakh crore be 1,00,000,00,00,000? How do you get to 10,00,00,00,00,000 by applying the same rules that apply to lakh and crore?
But now the written form of the number is completely disconnected from the spoken form. That means you have to write out the whole number first, and then go back through and add separators in random locations.
It's a rule that will tell you how to write "any number" equally, but it makes all the numbers inconsistent with each other.
I think (I'm no expert) 1000 made sense at the time. All of measurement seems to be more or less made up on the spot, and everybody agrees to stick with those units. Nice short writeup of the history of length here[1]. I'm not knocking metric, and I agree 1000 is nice. From our current understanding of everything, it all holds together really well. But I think that was pretty true of all units of measure that lasted any length of time.
My graduate advisor loved slipping it into papers just to show it off. I had to dissuade him at least once because it was in the middle of a table of percentages and who is going to that the 7th entry out of 12 has ‰ instead of %?
Blood-alcohol levels are typically measured as permilles in some countries, like Sweden. 0.2 ‰ is the legal limit there. Also used in some countries in Europe to denote the grade of slopes (as in warning for steep hills).
Are you telling me that a Ronnagram isn't a message from Ron, delivered by Western Union? And for stuff like the mass of the earth, why not 6e27 kg or whatever it is, instead of these weird incantations? Ugh.
"(...) he had the idea for the update when he saw media reports using unsanctioned prefixes for data storage such as brontobytes and hellabytes. (...)" and "The only letters that were not used for other units or other symbols were R and Q"
So it seems the new prefixes are partly initiated by the exponential computer storage needs rather than scientific needs. So they might need to move again soon. However the SI has exhausted the available stock of letters. Maybe Greek letters next time like micro for 10^-6.
Anyway does it really matter for IT people? I have seen so many people mixing up bit and byte, milli- and mega- as well. There are countless usages of mb all over the Internet to express MB.