Hacker News Reader

Comment by phicoh | Hacker News Reader

In the context of the metric system, the problem is that the second and the 'day' don't line up. From a human time keeping point of view, days and fractions of days would be ideal.

However, actual days are nowhere close to a fixed amount of time. And for historical reasons we are stuck with a very precisely defined second that is based on 24 hours in a day.

So the obvious approach would be to define a new unit of time that is roughly equivalent to a milli- or microday.

But the chance of that happening is close to zero.

So we are stuck with the second as the fundamental unit of time. Having a 'centiday' as 864 seconds would be even more removed from the principles of the metric system than a 3600 second hour.

View on HN

Sci-fi writers, most notably Vernor Vinge, have played with Metric Time [1] of the modern sort of being entirely second-based.

It's interesting because it particularly exposes interesting flaws in using metric prefixes (that are sometimes also talked about in the world of grams where kilograms are the closer unit to most "human applicability" and that a more human scale would possibly have more prefixes near kilogram than gram). Particularly the magnitude jump from a kilosecond (16.7 minutes, about a quarter hour) to megasecond (11.6 days, nearly a fortnight).

I've heard fun proposals that if Metric Time based on seconds were to be more useful on human timescales to bring back the deceased Metric prefix myria- [2]. A myriasecond is 167 minutes or just less than three hours (2.78). Maybe a prefix for the next digit as well (10^5) which would be just more than a day, by about an eighth of a day (27.8 hours).

[1] https://en.wikipedia.org/wiki/Metric_time

[2] https://en.wikipedia.org/wiki/Myria-

It is mainly what we are used to. For power we have kilowatt, megawatt, gigawatt, no problem. For gram, meter and second, we have milli, micro, nano, etc. no problem.

But we don't have megagram, megameter because we not used to it.

Just like you can easily talk about 10 km, 20 km, etc. you could easily talk about 10 ks, 20 ks, etc. no need for a special name. We are just not used to it.

It's not just about what we are used to. The argument about where the "central" point in the scale matters (for seconds and for grams) because the prefixes are by their very nature logarithmic, with "easier" distinctions made close to the center point/0-point on the scale axis than further away in the scale.

milli-, centi-, deci-, deca-, hecto-, kilo- are all six very close surrounding the 0-point/origin. Everything else gets logarithmically further out.

Using second as the 0-point is great for computation, as milliseconds and even microseconds can matter to a computer, but it isn't great for the human perception of time where people are bad at even granulizing events that happen in deciseconds, leaving nearly all of the decimal prefixes almost useless in human timescales.

Which is why you see the French Decimal Time system mentioned in the article here and used by the poster above in this thread centered around the day as its 0-point. milliday, centiday, deciday, decaday, hectoday, and even kiloday are all relatively useful units in a human timescale.

While you are correct that we don't "need" that kind of vocabulary, the argument is that it would be useful in conversation and in day-to-day (fig. and lit.) math. Having additional prefixes serves as mental anchors/frames for the conversation. If I give a number of seconds to you as hundreds of milliseconds versus deciseconds, that gives you additional context about my methodology and/or focus in whatever that benchmark was. Sure, you can easily convert between the two prefixes, but that context can be useful.

Just as the difference between if I tell you something is happening in hundreds of minutes from now versus threes of hours from now. There's probably a useful contextual distinction there. That's why people play with solutions like Decimal Time changing the scale altogether away from seconds to something more like an Earth day, or in the other direction explore ideas with more prefixes to fill in some of the logarithmic "gaps" such as myria- and hebdo-.

I'd say that for time, the second is the only thing people can really relate to. With a bit of practice everybody can count seconds. We cannot related to minutes, hours, day, etc. without an external time keeping source.

The other thing worth point out is that, though we have centi-, deci-, deca-, and hecto- they get only limited use in practice.

Very few distances are specified in deca- or hectometers.

Very few things are decagrams. There is a metric ounce and pound. But hectogram is not used.

So for distance, we have meter, kilometer. For mass, gram, kilogram, metric tonne.

Within the same system, we could easily deal with kiloseconds and megaseconds.

As far as I know, nobdy uses deciseconds as something other than a weird way of saying 100 milliseconds.

In informal speech, the number of zeros is used as estimate of precision. Using prefixes to specify precision is way too confusing.

Within the metric system, 10 kilosecond would roughly be the same as 3 hours. With a single day, everybody could easily adapt to kiloseconds. The problem starts when you have to create a system of timekeeping based on metric second.

> I'd say that for time, the second is the only thing people can really relate to. With a bit of practice everybody can count seconds.

Not really. Games like "one Mississippi" are fun approximations, but they aren't terribly accurate. Also this gets very close to the argument that foot is a better unit for length than meter because you can more easily approximate it with the average adult male's shoe length. Easy to approximate has its uses, but also doesn't necessarily make it the best fit for every application.

Scheduling is a critical component to people needing time, and yes is just about impossible without clocks / calendars / sundials / other "external sources". But that's also where all the interesting stuff happens when people use time and if you can't account for the math of scheduling, people would never use that unit for time.

Part of the problem there is that we do keep trying to "square the circle" if we want to apply metric tendencies to our reference points on rotating spheroids. (Another fun experiment I've seen in sci-fi, and played with myself, is the idea of day time expressed in radians.)

Indeed, using the day as the fundamental unit may be a nice choice for humans on this planet as a personal system, it's equivalent to looking up and telling the time by the position of the sun in the sky, but it's not accurate nor regular due to celestial mechanics, so the second used by the metric system is much more universal and unlikely to change anytime soon.

Thanks to our computers that keep track of every seconds elapsed since Unix Epoch, I can use them when I want to convert from my personal system to any other system or vice versa:

  $ geodate 51.1789 -1.8262 $(date +%s --date "12:00 +0100") --format "%c:%b"
  45:33

hours:seconds => timestamp => centidays:dimidays

Reply on news.ycombinator.com