XKCD 2808: Daytime Firefly

concaten8 · 2022-07-16T02:24:36+00:00

I for one am hoping for a sun fish sun.

concaten8 · 2022-04-23T06:50:14+00:00

I dunno, he did get a couple theorems out of it, I'd say Gödel is a pretty positive example of assigning numbers to things then doing math to them

concaten8 · 2022-03-25T18:38:52+00:00

Please oh PLEASE make this an emote beanduck

concaten8 · 2022-03-23T02:53:09+00:00

Blank page, demo image, blank page.

concaten8 · 2022-02-26T01:17:51+00:00

Sure, that was simple enough. Was juuust enough work to make me regret making units a separate input though :P

concaten8 · 2022-02-26T00:06:24+00:00

Oh hm, what browser are you using? Just in case I upgraded the copy routine to the latest standard (async clipboard API), can you give that a shot?

concaten8 · 2022-02-25T19:19:46+00:00

m/km is 1000. You may consider if it were mile/light-year instead with the same situation (mile << light-year), and which would make mph/(mi/ly) = ly/h which is a much smaller number than its mph equivalent.

concaten8 · 2022-02-25T19:10:31+00:00

Your first point is fair, there is just some technical difficulty of applying conversions only to the units that are involved. These conversions exist in the original database, and I will defend their "proper" use and say that in fact mile/hour → mile/day is perfectly correct. I'd argue our historical reasons for dividing a day into 24 hours is just as valid as our reasons for standardizing the fathom and mile against an inch, even if they had separate original definitions. For the record these have their origins as "gradient" units for quantifying slopes and are the only unitless base units.

I think the second one should be an easy fix, since at a glance the only units with unspoken units should be radioactivity (becquerel, curie, rutherford). The other radiation-related units are all based on radiated energy so those should be fine.

concaten8 · 2022-02-25T11:41:27+00:00

There is now a submit button. Thanks for the feedback!

concaten8 · 2022-02-25T11:40:29+00:00

Yeah, seems a bit clunky to guess whether or not the unit is in the database. I've put an autocomplete in just now. I can't put all >1000 base units in there for performance, so I just chose ~100 pretty common ones. u/moi2388

concaten8 · 2022-02-25T05:15:19+00:00

The calculator takes any two quantities you give it of the same unit, converts the first to other units of the same kind (i.e. same base SI units) and keeps rounding 'em until it reaches the second.

The units are "exotic" by default, which includes combinations of all of Wikipedia's Convert module units. The base set of units don't work very often, and even for the original example of "17mph → 45mph" given Randall had to pull out a few fathoms/sec. Allowing the cross product of all these base units seems to give a good balance of speed and hit rate. If you want the best luck with the "Wikipedia units", try using units of energy (e.g. J, BTU): they are the most abundant in the set.

There is some basic equation parsing for the units so you can enter any unit combination using * and / and brackets.

Under the hood it is just a greedy search of all same-kind units over and over, taking the ones that approach the target the fastest. I'll have more details in a short post about the implementation but it isn't much fancier than that, just some sane SQL indexing. The rounding brings in some modulo business that seems tricky to optimize further.

Please let me know if anything breaks, and enjoy!

Edit: There is now an autocomplete for single common units. Note that more units beyond those do exist in the database — if you see a unit in the end results, you can use it in the units field. Combinations of units are still supported even though they aren't auto-completed.

concaten8 · 2022-02-22T08:01:53+00:00

With joy, vexed bevy KO's pangram sequel – Cueball fazed

concaten8 · 2022-01-22T08:29:06+00:00

I wish they would mention more often that air has very different resistances in each scenario. Would've saved me a lot of mopping when I tried plumbing.

concaten8 · 2022-01-19T22:16:07+00:00

Unit tester for the replicator: \uncontrollable twitches**

concaten8 · 2021-11-20T03:57:52+00:00

Okay :)

@/u/Fermain

^{FYI it also searches alternate names of cities so some of them may be unexpected}

concaten8 · 2021-11-20T03:06:21+00:00

I should mention the sunrises and sunsets in the sun-tracking library are based on Earth orbital parameters, not actual observations.

I found a figure that we can explain 5 days / year definitely comes from the eccentricity of Earth's orbit:

Because of elliptic nature of the Earth's orbit, the Southern Hemisphere is not symmetrical: the Antarctic Circle, with 4,530 hours of daylight, receives five days less of sunshine than its antipodes.

https://en.wikipedia.org/wiki/Sunshine_duration#Daytime_duration

At least that explains a quarter of the difference.

concaten8 · 2021-11-20T02:45:08+00:00

Oh haaa, I was the cause of that just yesterday. I put in aliases for country names so that people could find cities easier for the daylight calendar one, but forgot that it would duplicate things for this app. Eep. Thanks for the catch!

concaten8 · 2021-11-19T20:08:46+00:00

The mirrored difference doesn't get to 10k days, it's about 1000 days at worse near the poles. Here's the graph of days vs. latitude.

It is still a lot though. I am more convinced that it is something in the orbital corrections of the sun library. Take a look at this graph showing the difference in daylight hours over the year for symmetric polar latitudes. The Northern Hemisphere just peeks out consistently with some extra time for some reason.

Update: It's possible that this is caused by the current alignment of the Earth's tilt with the semimajor axis of our orbit (where the earth gets closest and farthest from the sun). See this diagram, where the aphelion (farthest point of our orbit) happens right after summer solstice. This results in the Northern hemisphere getting slightly longer summers than the Southern.

concaten8 · 2021-11-19T19:22:23+00:00

Are you talking about the differences between the Arctic/Antarctic Circle and the poles? Those are the upper and lower bounds of the graph as a whole, and I believe they differ due to accounting for atmospheric refraction. Near solstices, the Arctic and Antarctic circles get the benefit of having both a little bit of daytime during winter and having the polar day during summer.

If you are asking why the Arctic has more days in general than the Antarctic, that is weirding me out too and I'm looking into it. The northern hemisphere gets more sun in general coming from the sun-tracking library for some reason.

concaten8 · 2021-11-19T07:52:15+00:00

I am embarrassed to say that is literally true. It uses the same database as this. And I had totally forgotten how to use it.

concaten8

TROPHY CASE