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Show HN: I created Units Converter that contains 5000 units across 78 categories

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Re: Show HN: I created Units Converter that contains 5000 units across 78 categories

#91

Post by ars »

fsh wrote: post #55
alok99 wrote: post #48

Earlier quoted context omitted.

The editorial on Hz is particularly funny and insightful. // Beware the SI's broken definition // of Hz. You should treat the radian as being correct, as a fundamental // dimensionless property of the universe that falls out of pure math like // the Taylor series for sin[x], and you should treat the Hz as being a // fundamental property of incompetence by committee. ... // You are perfectly right. You are perfectly w…

I don't find this rambling insightful at all. Here is what the BIPM actually says about the topic: The SI unit of frequency is hertz, the SI unit of angular velocity and angular frequency is radian per second, and the SI unit of activity is becquerel, implying counts per second. Although it is formally correct to write all three of these units as the reciprocal second, the use of the different names emphasizes the di…

The Hubble Constant is also in HZ.

And its reciprocal looks like the age of the universe (apparently this is just a coincidence).

Re: Show HN: I created Units Converter that contains 5000 units across 78 categories

#92

Post by [deleted] »

bragr wrote: post #75
lostlogin wrote: post #69

Earlier quoted context omitted.

Are US teaspoons actually a different size to UK ones, or just the volume measurements?

1 US teaspoon is about 14.8 ml 1 UK teaspoon is about 17.8 ml. It goes on: 1 US gallon is about 0.83 imperial gallons

[deleted]

Re: Show HN: I created Units Converter that contains 5000 units across 78 categories

#93

Post by jonwiseman »

heisenzombie wrote: post #89
fsh wrote: post #55

Earlier quoted context omitted.

I don't find this rambling insightful at all. Here is what the BIPM actually says about the topic: The SI unit of frequency is hertz, the SI unit of angular velocity and angular frequency is radian per second, and the SI unit of activity is becquerel, implying counts per second. Although it is formally correct to write all three of these units as the reciprocal second, the use of the different names emphasizes the di…

Right, you can explain it but that doesn’t make it elegant. This is the equivalent of a function with a comment in it saying “Here be dragons!”. One very desirable property of a units system is that incompatible quantities have incompatible units. So if I try to add 1 Joule (== 1 kg⋅m^2⋅s^−2) to 1 meter, I’m obviously doing something wrong and I just can’t continue. But in SI I can take 1 Hertz (==1 s^-1) and add it…

That sum to me is both physical and not nonsense, and I think your interpretation is wrong. 1 radian/second != 1 s^-1, but instead ≈ 0.159155 Hz. This is from interpreting a radian as a ratio, in which "doing" one radian in one second is only going over 1/2pi of a whole in a second. So 1 Hz + 1 radian/second, physically and sensibly to me, means ≈ 1.159155 Hz.

Re: Show HN: I created Units Converter that contains 5000 units across 78 categories

#94

Post by whartung »

amenghra wrote: post #83
whartung wrote: post #57

Has anyone found a more elegant treatment of calculating with units than the HP calculators? I'd love to have an HP48 CLI to do unit calcs with. .5 * 10_m/s^2 * (15_s)^2 = 1125_m Admittedly, the HPs interim results are a bit of a mess: sqrt(6.673E-11_N*m^2/kg^2 * 5.98E24_kg / 6780_km) = 242603.08_N^.5*m/(kg^.5*km^.5) But, this converts cleanly to m/s: 7671.8m/s Everything else I've found have been just super fiddly.

Give https://numpad.io/ a try. It's not a CLI though.

This is very nice, thanks!

Re: Show HN: I created Units Converter that contains 5000 units across 78 categories

#96

Post by tobinfricke »

irrational wrote: post #10

TIL that there are Tablespoons [Metric]. Also, I thought "Library of Congress" was a standard unit of measurement? Not to mention the "standard reference pear".

In Germany I encountered the "metric pound" - you can order a Pfund (500g) of beef at the butcher for example.

Re: Show HN: I created Units Converter that contains 5000 units across 78 categories

#97

Post by tobinfricke »

saalweachter wrote: post #85
lostlogin wrote: post #69

Earlier quoted context omitted.

Are US teaspoons actually a different size to UK ones, or just the volume measurements?

Teaspoons aren't particularly common in the US. If you do need to stir a beverage or add sugar, you typically use a tablespoon.

Yeah, this isn't true. A teaspoon is a standard unit of measurement in US cooking.

Re: Show HN: I created Units Converter that contains 5000 units across 78 categories

#98

Post by HWR_14 »

mojomark wrote: post #47
askiiart wrote: post #6

Good to see the completely realistic terabytes/nanosecond is included! I'm sure messing around with that will never get old.

I'm not sure I understand the sarcasm (i.e. why TB/ns is an unrealistic A.) ...one gram of DNA can store up to 215 Petabytes or [215,000 Terabytes], knowing that the human being has about 600 grams of DNA [129,000,000 TB]. (1) B.) Now assume a human is traveling at the speed of sound in air on earth (~343m/s): 343 m/s * 129,000,000 TB * 1/1,000,000,000 s/ns, The result is that for every kilometer the human travels at…

Most of the DNA is redundant copies. We need the amount of DNA in a single cell.

Re: Show HN: I created Units Converter that contains 5000 units across 78 categories

#99

Post by mojomark »

lostlogin wrote: post #76
mojomark wrote: post #47

Earlier quoted context omitted.

I'm not sure I understand the sarcasm (i.e. why TB/ns is an unrealistic A.) ...one gram of DNA can store up to 215 Petabytes or [215,000 Terabytes], knowing that the human being has about 600 grams of DNA [129,000,000 TB]. (1) B.) Now assume a human is traveling at the speed of sound in air on earth (~343m/s): 343 m/s * 129,000,000 TB * 1/1,000,000,000 s/ns, The result is that for every kilometer the human travels at…

The only problem is getting useful data into and out of the human.

Meh, it was just an example. The point is that extremely dense data storage is now concievable, though perhaps not yet practical (e.g. using a "DNA drive") so this magnitude of units has it's place in the real world.

Re: Show HN: I created Units Converter that contains 5000 units across 78 categories

#100

Post by whatshisface »

jonwiseman wrote: post #93
heisenzombie wrote: post #89

Earlier quoted context omitted.

Right, you can explain it but that doesn’t make it elegant. This is the equivalent of a function with a comment in it saying “Here be dragons!”. One very desirable property of a units system is that incompatible quantities have incompatible units. So if I try to add 1 Joule (== 1 kg⋅m^2⋅s^−2) to 1 meter, I’m obviously doing something wrong and I just can’t continue. But in SI I can take 1 Hertz (==1 s^-1) and add it…

That sum to me is both physical and not nonsense, and I think your interpretation is wrong. 1 radian/second != 1 s^-1, but instead ≈ 0.159155 Hz. This is from interpreting a radian as a ratio, in which "doing" one radian in one second is only going over 1/2pi of a whole in a second. So 1 Hz + 1 radian/second, physically and sensibly to me, means ≈ 1.159155 Hz.

I am afraid you may have misunderstood them. It's not that you can't add a centimeter to an inch, it's that you have to convert units first. The unit symbols are intended to help indicate when a unit conversion would be necessary. What many find confusing is the fact that Hz and rad/s are both (in terms of basic physical units) advertised as s^-1.

To resolve the issue, you could define 1Hz as 2pi/s on the grounds that the Taylor series for sin(t) is in "units" of rad/s. You could also define one rad/s as 1/(2pi s), arguing that since the becquerel is 1/s and means "the number of times something happens per second," it would be inconsistent for frequencies to be denominated other ways, and that Hz is applicable to functions other than sin(t), including square and triangle waves, which have no relationship to angles.

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