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this post was submitted on 24 Sep 2023
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The metre was originally defined in 1791 (...) as one ten-millionth of the distance from the equator to the North Pole along a great circle, so the Earth's circumference is approximately 40000 km.
https://en.m.wikipedia.org/wiki/Metre
The kilogram was originally defined in 1795 during the French Revolution as the mass of one litre (1/1000 m³) of water.
https://en.m.wikipedia.org/wiki/Kilogram
... and the last major SI unit is the second which of course you know is (originally was) 1/86400 day.
Please notice about the Celsius scale : the second reference point isn't a mixture of ice and salt but rather pure water freezing point.
Now how can we as naked humans develop technology to figure this out is something of historical proportion, that's a quite amazing story !
Your definition of the meter leaves out the most interesting part. Yes, it was 1,000, 000th the distance of the equator to the North Pole, but how far is that? That wasn't known accurately in the 18th Century. So, two Frenchmen, Delambre and Mechain conducted the longest meridian survey every attempted. They also did so while half of Europe was at war with one another. It was an amazingly dangerous endeavor. There is also significant evidence they totally flubbed and hand-waived their results. So, although their science ended up being questioned, the process and method was accepted and the Meter was defined.
Re Celsius 0 °: the reason I thought perhaps Fahrenheit's Weird Brine might be a more absolute thing to take de novo temperature from was because I don't actually know the answer to "how can you ensure water is exactly freezing temperature?" If it's solid ice it could be colder, if it's liquid it's probably warmer, and even if it's a bucket of cold distilled water with distilled water ice in it, isn't it still likely hotter than 0 ° C? I feel like there's probably something involving equilibrium between solid and liquid water that would be difficult to sus out
Not that Weird Brine is any better really 🤦♀️
if you have both liquid and solid water at equilibrium then you have zero degrees Celsius. Pressure has minimal effects ...at plus or minus 0.5 atmosphere. of course if you go to a hundred or a thousand atmosphere then there is an effect of pressure.
Small pieces of ice will equilibrate their temperature faster in water.
Surface tension has minimal effect on melting temperature unless you go to extremely small pieces of ice meaning less than one micron, ...which is not possible to achieve anyway because such small ice pellet with fuse rapidly to form larger ones.
Ah, so at sea level a bucket of ice water would make a decent approximation of 0 ° C, then, I suppose.
Didn't know really tiny ice particles spontaneously fused, this is neat to know
Yes a bucket of a mixture of small ice pellets, say a few millimeter size, plus water, (this bucket being enveloped with some insulation) would be a great zero degrees Celsius reference point.
if you want something more precise you can read this :
https://en.m.wikipedia.org/wiki/Celsius
isotopic distribution of heavy and light elements in water also has a very slight effect on melting point. So, rainwater and water distilled from ocean will not melt at the (exact) same temperature.
See : Vienna Standard Mean Ocean Water https://en.m.wikipedia.org/wiki/Vienna_Standard_Mean_Ocean_Water
Now, about small particle fusing together this is true not only of ice but of any material.
it's called sintering and it is caused by diffusion and a lowering of the surface energy.
This process is faster when the material is near it's melting temperature and faster yet if in contact with any miscible liquid phase.
Can we improve things a bit? Hoping we can get a calendar with no leap year, even number of days in each month, no daylight savings, etc
Edit: obviously no one got what i meant. We can base the day of the year on whatever the fuck you want, but for the love of god can we not split it into twelve randomly numbered chunks, i hate how our months are!!
There is a calendar that proposes to have 13 months, each with 28 days. That gives you 364 days. Day 365 is new years day and is not part of any month. There are still leap years because as stated, the Earth goes around the sun in 365.24... days. To not need leap years we'd need that to be a whole number.
I really like that one! Guess there's really no easy way around leap day, but i was thinking you could add an extra ~60.684 seconds to each day and pretend its the same thing? Even increasing the second to be slightly longer could make it possible i think, since we are restarting from scratch it would be easier to adjust it slightly
Assuming you can measure that precisely. We had to wait centuries to figure out the differebce between a solar and a sideral day.
Then change how years or days are defined or something. I demand a reasonable system ffs
Well pretty much everyone likes defining a day based on the position of the sun in the sky. While sun rise and sunset might change over the course of the year, nearly everyone agrees that noon is when the sun is the highest in the sky (ignoring day light savings and time zone effects). Turns out people don't like it when noon occurs in the middle of the night (which would happen if we changes it to any other length of time).
Likewise, nearly everyone has agreed for millenia that a year is defined by earth's position within its orbit. We know that based on where the stars are at night. Again, people didn't like having snow during July (which actually happened because the calendar was so far off).
These are not definitions that we can change or have any control over. Additionally, the length of a year (to get earth back to the same spot in its orbit) divided by the length of a day (the time between the sun reaching its apex one day and the next) is not an integer and there's nothing that says it has to be.
We can't change it, so if thats important to you, you'll have to find another planet to live on.
I know what "we like". I am saying we should change it in a hypothetical post-apocalyptic scenario where humanity joins hands together and demand a yearly calendar that makes more sense. Don't know why this is getting downvoted, guess you're all taking me wayy too seriously lol
I'm personally not voting on your comments, but you are probably being down voted because you are either being purposefully ignorant or you are continuing to insist on a "better system" that is physically impossible.
How is a better system impossible? Lets say you are on a star ship, heading away from earth, no reference points besides distant stars. How do you determine time? How do you determine anything? Even if we knew and simulated exactly how fast the earth is spinning and how much it is rotating around the sun, it means nothing out there. We have decided that time works the way it does, all I am asking is to take the extra .24 days in a year and make them disappear. There are several inconvenient ways to do this but it is possible to break it down further so we do not need the extra day. We could round it off to the nearest day every few years, shrug our shoulders and move on with our lives without tacking on another 29th day in some random month? Maybe there is some other way we haven't thought of? I guess I just thought more people would respond positively to "impossible future scenario where a calendar that makes sense is used" :/
Sure, in that scenario, such a system would be possible. Hopefully, there is still an earth to communicate with however. So we'd have to keep using earth days and years to enable effective communication. Also, the entire ship would have been built using earth based units, so it might be easier to use the system we've already got.
We're not on a space ship though. We're on Earth, so what happens on this planet matters. You may care more about not having leap years, but the majority of us care about knowing approximately what the weather will look like at a given point in time and how much sunlight to expect, since those things actually affect our daily lives, whereas an extra day in a given month does not.
What about when in the future if we needed to, say, sync time between here and mars, it would make it easier if we had some "frame of reference" outside of the sun maybe. There would basically just need to be a slight redefinition of what a day is, to account for the extra quarter of a day each year, its only a minute each day, ~86,460 seconds in a day instead of 86,400. Not exactly gonna throw the weather/sun off, no?
You can come up with new timekeeping systems when you need them. It's not like we can't convert between them.
Then two years later, the sun will be at its peak at midnight.
I guess thats true, but in the Stone age they can just deal with that lol
oh i know the answer. Since a mars day is about 15 minutes longer and out rover there are solar powered it was important that the human operators of them knew what time it was on mars. Nasa's answer, make a watch that runs about 2% slower. that git the mars watch an extra 15 minutes and so it syncs to the martian sun.
Figured there would be an answer like this, thanks!
you just have the ship day be the same length as an earth day and start count from day 0. So the ship launches and it clock starts ticking. Now you do need to ask is this going fast enough that time dilation is a thing? That will change how well it can ever sync up to earth.
A ritual calendar would work. How long is a year, say the length of a human pregnancy. How long is a month, one tenth of a year.
Boom no more leap years or leap months and no more tracking solstices.
This would need the Earth to make one complete rotation around the Sun in an exact whole number of times it rotates around itself. ...which is not the case right now and extremely difficult (meaning near impossible) to change.
Okay but now we have a greater problem : we have to change (twice, a year) the time when business, school , stores etc... open and close, for it to be convenient with outside natural light. So, in my opinion, this is not an improvement.
Nah fuck it, change something, its all made up anyways!! The whole idea of our "years" doesn't make any sense on other planets, so we potentially could define some arbitrary system to it.
Not sure if you're joking or just having a slow day, but neither the length of a day nor the length of a year are arbitrary. One is the length of a revolution of the earth around its own axis, the other is the time the earth takes to complete a full run around the sun. Those two aren't fully in sync, and to line them up would require a major feat of astroengineering. Given sufficient advances in science, we might get there in a few millennia, if we're still around by then, but until then leap years are here to stay.
Look, i know what it is based on now, I am saying we should change it. Obviously I am not being super serious, but it would be nice to have even numbers instead of how it is now