What calendar has 365 days in every year?
Andy_L’s post that I was replying to claimed that the length of a “year” is 31,536,000 seconds, which equals exactly 365 days of 86,400 seconds per day. Of course the Gregorian calendar periodically adds leap days to keep the calendar year roughly in sync with the tropical year, so one can say that there is no single “length” of a calendar year. My point was that since the calendar year is defined as a number of days, not a number of seconds, the length of a calendar year changes when the length of any of its constituent days changes. At least that’s how we’re currently handling it.
Certainly not 1752.
But it doesn’t. The calendar is carefully crafted with the appropriate formula for leap days to keep the year equal to a trip around the sun. That’s why we lost 11 days in 1752 - things were getting out of sync. If the length of the year gets off line for whatever reason, we’ll adjust the formula for leap days to keep the year in alignment. We’ve done so several times in the past.
No problem
I did say “about 31,536,000 seconds.” I should have said “About 31 million seconds” (though all the definitions of a year length are within less than one percent of 31536000)
Back when I was in high school and university and memorized constants for fun when a lecture was repeating material I already knew, I memorized the length of a year in seconds. 31 556 925.9747 seconds. At least that’s what you got if you entered the value 1 year in a HP 48SX calculator and converted that value to seconds. I have not found a standard that corresponds to that peculiarly precise value.
Is that why I felt dizzy getting up this morning?
But if the earth spins faster, clocks will relativistically slow down.
Argh my brain!
Except, if it spins faster, it will fling off more stuff, losing more mass than it is now, and that will reduce gravity, causing clocks to run faster.
Did you also memorize Avogadro’s Number, down to the units digit?
No. I didn’t like chemistry. There are 9 billion 192 million 547? thousand 631 cycles of radiation from Cs 133 in a second though. Yeah, that one has slipped away at some point in the last 20 years, it’s 9,192,631,770.
There is no mystical force moving water towards the poles. Water seeks it’s own level.
The most logical reason could be some event that moves substantial mass closer to the earth’s axis. This could be a humongous landslide or a mega dam breach.
If the water formerly in the Amazon basin, which lies at the equator, has distributed itself over the rest of the world in the oceans a big part of it will be closer to the poles and all of it will be at a lower level than the Amazon, I don’t understand that you don’t visualize that. The amount of water on Earth is given, a dry Amazon means a wetter place somewhere else. That is not a mystical force, it is just spreading around the globe.
When you said water moved from the equator closer to the poles, I assumed you meant the water in the oceans at the equator had mysteriously migrated towards the poles.
I googled “water level amazon basin”. The first article was from this June with the headline, “In Brazil’s Amazon, rivers rise to record levels” which means that there is more water than normal at the equator in South America. So that’s not why the earth is revolving a tad faster than it was in 1900 (the base year).
No problem. I just went with the OP, who stated in his opening statement that
and was answering this assertion:
Of course, if the Amazon basin is not getting drier (which I did not check, my bad) my explanation becomes pointless.
And, just as an afterthought, if the poles are melting that water will distribute over the whole Earth too, so partly to the equator, which should slow the rotation down. Only that is not what the data show. Which just goes to show that the subject is not evident or easy and that the OP made a good point: Stuff for thought here! Nice, thank you naita!
The entire hydrosphere of the Earth is an extremely thin layer that, including water within the planet, amounts to about 0.023% of the total mass of the planet. It seems profoundly unlikely that any amount of that could have even a ns-scale effect on the planet’s spin.
My hypothesis:
Over the long haul, the Earth is slowing down - which means that the shape of the Earth last century is a little “wrong” for the current rotation of the planet. Over time, at discontinuous moments, the physical shape of the Earth alters to match the new slower speed of the Earth, by shifting mass towards the poles (a slower earth is less oblate). But shifting matter to the poles speeds up the Earth – so superimposed on the long-term slowing of the Earth, there are occasional periods of short term speeding up, as the core, mantle and crust try to keep up with the perfect hydrostatic shape, but are restrained from instant response by friction and their own resistance to deformation.
The Egyptian civil calendar used by many ancient astronomers such as Claudius Ptolemy for its computational convenience. You’re welcome!
Well, a day has 86,400 seconds, and the change is 1.4602mS, so the difference in rotation rate is 0.000044%. It’s not obvious to me that removing 10^15 kg of water from the atmosphere, as a La Niña can apparently do, wouldn’t be able to do that.
I was going to do the math, but searching for some of the variables turned up this:
They claim that El Niño slows the earth becauss of differential pressure on mountain ranges creating a torque that slows rotation. Sounds goofy to me.
Here’s a better cite which agrees that El Niño and La Niña speed up/slow down the Earth by easily the amount we’re talking about, but they don’t give a hard reason. One hypothesis they mention is potentially a change in ocean currents opposing the rotation of the Earth, and I guess by converting angular momentum to heat? Other scientists disagree with the exact mechanism, but admit the change is real.
https://www.science.org/content/article/longer-days-brought-you-el-ni-o
And yet a third cite with a different cause:
They hypothesize that it’s a change in tropospheric winds that changes the angular momentum of the Earth. I find that one hard to buy as well, but I’m not sure.
I still like my water vapor theory, Adding or removing 10^15 kg of water to the atmosphere will definitely change Earth’s rotation rate, and I find that more plausible than high pressure on one side of the Himalayas ‘torquing’ the Earth. The question is whether the mass change is large enough.