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Comment by Timothycquinn | Hacker News Reader

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Timothycquinn

Please have one minute of silence to remember this wonderful machine that gave us all so much...

Kudos to all those who contributed to make this such an overwhelming success.

Science FTW.

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Earth minute or Martian minute?

Excellent question. I assumed that one mars minute differs from an earth minute but I just learned that they don't. Seconds, minutes and hours are universal. Hours in a day is what varies by planets, moons etc. Funny that I never thought of that before :)

Surely this is effected by relativity?

Edit: Or rather should I say it’s relative... (lol?)

It just depends on what your definition of a Martian minute is. If you define it as 1/(24*60) of a Martian day, it is different from an Earth minute.

You're likely joking, but just in case: on earth the second is not defined as a fraction of the day, it's a SI unit defined as a constant count of energy level variations of an caesium-133 atom.

What came first, the definition/concept/time span of a second,

or the discovery of the Caesium-133 atom?

Good question.

Counting minutes obviously came first as devices likes hourglass and water clocks are old (2000 BCE).

Regarding their precision, I got interested and per this paper [1] and the wikipedia page about traditional Chinese timekeeping [2], water clocks from two millennia ago might have around 15min precision.

For second level precision, it seems modern mechanical clocks were required, and they only precede the discovery of caesium by a few centuries.

[1] https://www.cambridge.org/core/services/aop-cambridge-core/c... [2] https://en.m.wikipedia.org/wiki/Traditional_Chinese_timekeep...

They said minute, not second. Even on Earth a minute isn't always 60 seconds.

How is this? According to the International System of Units, a minute is 60 seconds.

Leap seconds.

A minute is still 60 seconds. The only difference is that some clocks will occasiomally go an entire minute without incrementing their minute counter. This is a property of the map, not the territory.

You're choosing to define it that way when the entire point made here was that other people can and do define it other ways.

They change the duration of the day, not the minute.

The clock goes from 59:59 to 59:60...

Yeah. Or they smear it over a longer time period, but that still (slightly) extends the duration of each minute.

Thanks for that clarification. After this, I was able to find the International System of Units Wikipedia page which clearly defines a second as per your summary. It's a relief to see that it's a constant formula like that of the Kilogram.

I was suprised to learn (from the wiki page) that the kelvin, mole, and ampere do not have exact numerical definitions yet, though I guess that's expected to change in May of this year.

And then there's the candela, still basically defined by how luminous whale blubber is when it is burning:

> Current (1979): The luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 5.4×1014 hertz and that has a radiant intensity in that direction of 1 / 683 watt per steradian.

> Note: both old and new definitions are approximately the luminous intensity of a whale blubber candle burning modestly bright, in the late 19th century called a "candlepower" or a "candle".

What happens in May?

World Metrology Day, where acceptance of these standards will be voted on.

https://www.nist.gov/news-events/news/2018/11/historic-vote-...

Not if we take gravitational time dilation into account. But for most practical purposes between Earth and Mars, a minute will be the same.

>Not if we take gravitational time dilation into account.

I think most of us will be observing the minute of silence from Earth, either way ;)

Lol. Come on let us ... rip.

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