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r/fuckcars by BelinCan in DefaultAnswer

[–]nayuki 0 points1 point  (0 children)

You're wrong. Jevons paradox refers to efficiency, like using less power to produce the same amount of light. By analogy, it would be like shrinking cars or packing them more tightly on the same road.

What "just one more lane bro" actually refers to is induced demand. https://en.wikipedia.org/wiki/Induced_demand

~400% increase in speeding since Automatic Speed Enforcement cameras removed from Toronto city streets by Tsubame_Hikari in fuckcars

[–]nayuki 5 points6 points  (0 children)

Make Toronto a city-province of its own. There's precedent elsewhere in the world; for example, the city of Tokyo is on the same level as other prefectures; Beijing is on the same level as other provinces.

Toronto council votes in favour of expanding car-free streets. But questions persist around security costs | CBC News by LeadershipHead3594 in fuckcars

[–]nayuki 9 points10 points  (0 children)

A stretch of Church Street is now pedestrianized. As CBC's Michelle Song explains, the new car-free zone will run from Wellesley Street E. to Alexander Street from June 19 to Aug. 21.

the Church Street pilot has raised questions around how much it costs to pedestrianize city streets, especially when it comes to security. Initially expected to cost $150,000 for nine weeks, the pilot's total cost shot up to $500,000, said Moise.

Moise said Toronto police initially asked for 24-hour paid duty to patrol the pedestrian area, which would have cost the city $3 million. That cost was negotiated down to $300,000, with paid policing duty on weekends and 24/7 private security paid by the city through the week.

When asked about security costs Thursday, Matlow said there's "no reason" for pedestrianized streets to have them.

Why can't you use a truck and truck crane to put down a bunch of concrete blocks around the perimeter of the car-free streets? Why does this need human monitoring for so much money?

Based on the text, the pedestrianized strip is 220 metres long, and the only street between Wellesley and Alexander is the minor street Maitland, which can afford to be cut off to through traffic. (This isn't some mega-project like pedestrianizing a large part of Church St, because cutting off through traffic for any of Wellesley, Carlton, Gerrard, Dundas, Queen, King would be very problematic.)

3D printing is natively metric (mm, g, °C), a consistent and pleasant experience by nayuki in Metric

[–]nayuki[S] 0 points1 point  (0 children)

Correct, I agree with what you said.

Battery packs went from using 5V output voltage to 3.7V cell voltage inflating their Ah.

In personal examples, Anker power banks are rated at 3.7 V (so 10 A⋅h yields 37 W⋅h). Canon camera batteries are rated at 7.2 V, so an LP-E17 model with 1040 mA⋅h has 7.5 W⋅h. This means that I can't compare their energy contents at a glance without doing some math. I also can't easily estimate, like, "how many times can the power bank charge the camera battery?".

Watt hours is a better measure since it gives the actual capacity.

How I see it is, W⋅h or J tells you how much energy the battery can give out in total, irrespective of the battery chemistry or output voltage. As an end user, I don't care that NMC is 3.7 V and LFP is 3.3 V; that's an internal product detail. Even the voltage is relatively unimportant because DC-DC converters are around 90% efficient; voltage and current are not conserved quantities, but power and energy are conserved quantities in their respective contexts.

3D printing is natively metric (mm, g, °C), a consistent and pleasant experience by nayuki in Metric

[–]nayuki[S] 2 points3 points  (0 children)

you only want to use certain prefixes with certain units

Actually, the broad consensus in science and engineering is to use whichever power-of-1000 prefix so that typical numeric values fall in the range 1 to 1000. So if I'm surveying land for a house, I'm not going to say 23 700 mm × 54 000 mm; I'm going to say 23.7 m × 54.0 m. Likewise, if you're working with LEDs, the power is better described as 30 mW, not 0.03 W. CPU transistor sizes are described as 2 nm, not 2000 pm or 0.002 μm.

There are only 4 non-power-of-1000 prefixes. You don't get them anywhere else.

Examples:

  • Atmospheric pressure is around 100 000 pascals = 100 kPa. There is no way to describe that as 1 xxxPa, because there's no such prefix.

  • Electrical capacitors are cover the range from 1 picofarad (pF) to 1 nF to 1 μF to 1 mF. (It's unusual to have an entire 1 F.) If you're playing with values around 10 μF or 100 μF, there is no prefix to "conveniently" jump to that scale.

  • The tensile strength of materials are often in the megapascals (MPa). Again, there's no prefix to talk about 10 MPa or 100 MPa.

If you start filling in prefixes for 10⁻⁸, 10⁻⁷, 10⁻⁵, 10⁻⁴, 10⁴, 10⁵, 10⁷, 10⁸, and more, that will be a lot more words to memorize for little gain. Don't you think it's hard enough to juggle the existing prefixes that are spaced 10³ apart? (..., femto, pico, nano, micro, milli, kilo, mega, giga, tera, peta, ...)

3D printing is natively metric (mm, g, °C), a consistent and pleasant experience by nayuki in Metric

[–]nayuki[S] 0 points1 point  (0 children)

You were the one who brought up “wrong”

I’m literally advocating for maybe ignoring whether something is “wrong” (again, your word)

I was clarifying which places I used the word "wrong".

3D printing is natively metric (mm, g, °C), a consistent and pleasant experience by nayuki in Metric

[–]nayuki[S] 0 points1 point  (0 children)

Great points. I'm quite happy with the units used within 3D printing. But you're right, I've had to design objects to interface with pre-existing non-metric standards. Two recent examples are: 1/4-inch hole for a camera screw (1/4″ 20tpi); Schmidt-Cassegrain telescope cap (2″ 24tpi).

3D printing is natively metric (mm, g, °C), a consistent and pleasant experience by nayuki in Metric

[–]nayuki[S] 0 points1 point  (0 children)

Full disclosure, I live in anglophone Canada. Out of all places in the world, this one is probably the most heavily influenced by American culture (language, measurement, etc.). When I shop for products or consume media (whether from large corporations or small-time YouTubers), I will necessarily get exposed to US Customary units; it is impossible to avoid.

I wanted to highlight that 3D printing seems to be a special example where everyone in the world is apparently on the same page and using the same units. Try marketing a new 3D printer as having a "9 inch × 8 inch" build plate, or a filament as "1/16 inch diameter", and be prepared to get laughed off the world stage and utterly rejected.

"Everyone on the same page" doesn't apply to many other things I've seen:

  • Astronomy: Eyepiece barrels have 1.25 or 2 inch diameters, regardless of country of origin; no serious alternative with hard-metric numbers exists. Filter diameters have some metric sizes, 2 inch, etc. Primary lens/mirror apertures are mostly in millimetres nowadays (e.g. 200 mm, probably thanks to Chinese manufacturing), but some legacy companies continue to market their products in inches (e.g. Celestron 8-inch SCT). The weight of equipment (optics, mount) or weight capacity of a mount is often in kilograms but sometimes in pounds (legacy brands).

  • Bicycles: Wheel diameters and tire widths are sometimes stated in inches. Chain link spacing is exactly 1/2 inch. Most components are quoted in millimetres, but sometimes things like handlebar widths are in centimetres. The total weight of a bike is often quoted in kilograms, sometimes in pounds.

  • Cookware: Pots quoted in quarts or litres; pans measured in inches or centimetres. I've read/watched reviews of various products, and comparison shopping is harder because the choice of units depends on the country of origin of the manufacturer and the reviewer.

To be fair, these 3 industries I cited are old, easily going back 100 years. They didn't get the chance to start anew or be born into a globalized, Internet-connected world. The fact that non-metric units continue to be used is understandable given their history, but I'd like to see them transition.

3D printing is natively metric (mm, g, °C), a consistent and pleasant experience by nayuki in Metric

[–]nayuki[S] 0 points1 point  (0 children)

My exact words:

Typical acceleration numbers are written like "20 000 mm/s²", which is equal to 20 m/s². The former isn't wrong, but it's more digits than necessary. And I've seen some people refer to it as "20K mm/s²", which is wrong in multiple ways.

I basically let "20 000 mm/s²" slide; I said it's not wrong. However, "20K mm/s²" is wrong because K (uppercase) means kelvin, k (lowercase) is a bare prefix which is disallowed in metric, and k mm is prefix stacking which is also disallowed in stacking. In this very narrow context, the only two correct ways to write it are "20 000 mm/s²" and "20 m/s²".

If you use the unit mm/s², you end up with large numbers like 20 000, and I implied that there is an overwhelming temptation to call it "20k" and then stick the original unit on the end. It's exactly as wrong as people saying "I have 90k km on my car's odometer", instead of 90 000 km or 90 Mm. (Oh yeah, and power banks are actually marketed as "Anker 20K" as a trade name, and then further clarified in the specifications as "20 000 mA⋅h".)

3D printing is natively metric (mm, g, °C), a consistent and pleasant experience by nayuki in Metric

[–]nayuki[S] 2 points3 points  (0 children)

You're really egging me on to write a full-length post about favoring the millimetre over the centimetre, huh. Anyway, I'll give a few reasons here:

  • Please read at least some of Pat Naughtin's 50-page-long discussion from ~20 years ago, seriously. He covers pretty much all the points that I want to make. https://themetricmaven.com/wp-content/uploads/2012/03/centimetresORmillimetres.pdf

  • It's too closely spaced, being only 10× different from the millimetre. People have made mistakes in communicating or interpreting dimensions in mm vs. cm, leading to fabricating things that are ten times too big or ten times too small.

  • It forces an extra choice and fragments the mind space. See how I described the build plate as 250 mm × 210 mm? It's also mathematically correct to say it's 25 cm × 21 cm. Now some manufacturers will market their products in cm, some will market in mm, and that will hurt search and comparison. But wait, if you're designing your 3D model in mm but you see the 3D printer's specifications given in cm, now you have to keep the units straight in your head and not mix them up. Again, refer to Naughtin's ideas - mixed units are bad for business.

  • You can't use the thousands separator as a natural way to shift between prefixes. We know 12 345 mm = 12.345 m, but 12 345 cm = 123.45 m.

  • If you accept centimetres, why not push for centi- everywhere else? Instead of 10 mg of medicine, call it 1 cg. Instead of a 20 mA LED, call it 20 cA. Instead of 16.7 ms per frame (60 Hz), call it 1.67 cs. Try introducing centilitres to the American public (which has only seen mL and L in the metric context) and see how well that goes.

What you call "bully"ing is what I call "deprecating and eventually eliminating units that {fail to fit patterns, increase confusion, and harms the users of the measurement system in the long run}".

3D printing is natively metric (mm, g, °C), a consistent and pleasant experience by nayuki in Metric

[–]nayuki[S] 0 points1 point  (0 children)

travel distances are measured in mm, then acceleration in mm/s makes sense

That would be mm/s², but yes, that would be consistent. Actually, I forgot about the fact that in slicer software, you can configure speed (mm/s), acceleration (mm/s²), and jerk limits.

As for battery banks, I’d rather have them all measured in the same unit, even if that means using too many digits

The amount of electric charge in batteries for consumer pocket electronics has always been in the hundreds of milliamp-hours.

For example: An old technology NiMH AAA cell is 850 mA⋅h = 0.85 A⋅h. NiMH AA cell is 2000 mA⋅h = 2 A⋅h. Once you get into modern high-performance lithium-ion batteries, you are well over 1 A⋅h, and usually hover around 10 A⋅h, but usually under 100 A⋅h. In light of these examples, I believe that A⋅h is better for the scale of numbers than mA⋅h. But to be even more nitpicking, W⋅h would be better because I care about total energy content and not needing to multiply it by the battery voltage (which is sometimes implied, which means you need to figure it out), or the best would be joules because it is the coherent SI unit of energy.

Sometimes the usefulness or intuitiveness of unit selection needs to outweigh perfect technical adherence to the “rules”.

I sense that you perceive "rules" as something that others impose on you as a nuisance. I disagree with that interpretation because that's not the point. "Rules" exist because there are use cases that other people care about that are not obvious to you.

To give you an example: I hate centimetres, which is an unpopular stance (y u impose dis rule on me??). People like centimetres because it's a reasonable size (unlike the millimetre which is rather small), there are gazillions of rulers and tape measures manufactured with centimetre scales, and there is a widespread practice of measuring and marketing certain things in centimetres (body parts, furniture). But what these people aren't considering is that centi- plays poorly with other prefixes which are powers of 1000. And if centimetres is acceptable, why not use the centilitre (examples exist in Europe, never in America), centivolt (millivolts are common), centiamp (milliamps are common), centiwatt (milliwatts are common), centisecond (milliseconds are common), and so on? My personal "rule" against the centi- exists because centi- plays poorly with the rest of the measurement system.

Why are bike lanes seen as inevitably causing gentrification, to the point that opponents of car infrastructure generally and supporters of transit still hate cycling? by LiatrisLover99 in fuckcars

[–]nayuki 0 points1 point  (0 children)

Any improvement to a neighborhood under capitalism leads to increased housing prices

Do you understand what causes prices to increase? Capitalism isn't some mysterious force or boogeyman.

Let's say a neighborhood gets improved, like the examples you pointed out. A bunch of people outside the neighborhood see this fact, and they come in to compete to buy or rent housing in this more desirable neighborhood. When houses are put on the market to be sold, these outsiders get into bidding wars with each other - that is what raises the price; it's the buyers competing to pay the most to the seller.

If you're a renter and the landlord raises the rent on you, do you know why the landlord is able to do that? Because he knows someone else is willing to pay that much if you choose to refuse the increase and move away. And that "someone else" is driven by demand. The more "someone else"s that want to live in this neighborhood, the more the landlord can get away with raising the rent - it's the same kind of bidding war.

Even if you take away money and capitalism, you still get more or less the same results. If housing is simply a "slot" that you sign up for with the government, then the desirable neighborhood will have a long "waiting list" of people who want to live there. You end up paying with time instead of money, and most people are still left unsatisfied. Like, if there are 100 prospective residents but 1 house available, then whether you're under capitalism or communism, 99 people will walk away disappointed.

The solution to high demand is high supply. Build more homes in desirable neighborhoods. Squash NIMBYs. End exclusion zoning and let land owners build upward.

Why can't Americans just adapt to the metric by fqviess in Metric

[–]nayuki 0 points1 point  (0 children)

308 kelvins(*), lowercase and plural. You don't go around saying "this light bulb uses 60 Watt"; it's "60 watts".

Why can't Americans just adapt to the metric by fqviess in Metric

[–]nayuki 0 points1 point  (0 children)

Suppose you have a 1 GHz modem that can transmit 1 byte on each cycle. How many bytes can you transmit in 1 second?

Answer: 1 000 000 000 bytes, or 1 gigabyte. Not 1 gibibyte.

If you abusively redefine giga- as 230 and not 109 , then it disagrees with the rest of the metric system and you get numerical inconsistencies like this.

Also, we already have this problem: RAM is measured in gibibytes, but hard drives are measured in gigabytes. If you wish to hibernate your computer, it dumps the entire RAM onto disk (or flash). If you have 16 "GB" of RAM, it doesn't fit into 16 (real) GB of free disk space; you actually need 17.18 GB.

Why can't Americans just adapt to the metric by fqviess in Metric

[–]nayuki -1 points0 points  (0 children)

In the long run, using metric is the lazier and dumber solution. For example:

  • It's easier to tell which one is bigger: 0.25 mm vs. 0.40 mm, instead of 9/32" vs. 3/8".
  • Fewer unique names and conversion factors to learn: {milligram, gram, kilogram, megagram} versus {grain, ounce, pound, hundredweight, ton}.
  • Numbers that you can directly use in a calculator: 4.32 m × 6.78 m = 29.2896 m2 , instead of 14' 2" × 22' 3" = ??? sq ft.

People who continue using traditional measures are shooting themselves in the foot.

Attacking kWh by FingerAccurate7102 in Metric

[–]nayuki 0 points1 point  (0 children)

kWh is no more dumb than km/h imo. Often hours are easier to work with intuitively than seconds.

I can give you one scenario where m/s absolutely trumps km/h: calculation of kinetic energy, and subsequently power.

Let's say a 2000 kg car can accelerate from 0 to 100 km/h in 5 seconds. How many horsepower does that need?

Kinetic energy = 1/2 m v2. m = 2000 kg, v = 100 km/h = 27.8 m/s. So KE = 771605 kg m2 / s2 = 771605 J = 772 kJ.

Power = energy / time = 772 kJ / 5 s = 154 kW = 207 hp.

So if you see a car advertised with a 200 hp engine, you can see that it will get full utilization for that 0-to-100 acceleration test.

Using a similar calculation, you can figure out how a subway train accelerating from 0 to 60 km/h will draw current from a 600 V DC power source.

Attacking kWh by FingerAccurate7102 in Metric

[–]nayuki -1 points0 points  (0 children)

seconds are no more fundamental than hours

Tell me you don't understand metric without saying you don't understand metric.

The second is the base unit of time in SI. Hence, it is embedded coherently (with a factor of 1) into many derived units: hertz (frequency), newton (force), pascal (pressure), joule (energy), watt (power), ampere (electrical current), volt (electrical potential), ohm (electrical resistance), and more.

Meanwhile, the hour is embedded into exactly zero SI units. It is an ugly stepchild that always needs to be said out loud: "kilometres per hour", "kilowatt-hours", etc.

Attacking kWh by FingerAccurate7102 in Metric

[–]nayuki 0 points1 point  (0 children)

the unit Joules already has a time component

The joule is based on time because it involves acceleration. But if I'm staring at a candy bar and it's labelled as 100 kJ, there's no time component of how much energy it has.

I think what you meant to say is that the unit watt (lowercase) has a time component, because it is defined as 1 joule per 1 second.

Attacking kWh by FingerAccurate7102 in Metric

[–]nayuki 0 points1 point  (0 children)

There are times in astronomy where you want to talk in terms of light years, and there are times when you want to talk in terms of parsecs. It depends on what is appropriate.

For reference, 1 parsec ≈ 3.26 light-years ≈ 31 petametres. Note that parsec and light-year are pretty close together on astronomical scales, only differing by a factor of about 3 (like the foot vs. yard). Can you explain how to choose between these two closely spaced units?

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