The Earth is (contrary to expectations) spinning faster

Miscellaneous and Personal Stuff I Must Share
1

Long term the rotation of the Earth is getting slower, with energy being lost due to friction in the Earth-Moon system. We can measure the length of a day so accurately now that leap seconds are added or removed from time to time to keep the heavens in perfect synch with our daily activities (like we’d notice), but for decades the rate of change for the rotation has been slowing down, and last year it flipped.

This is probably due to changes in the distribution of mass globally. Basically the Earth is doing the equivalent to someone pulling their arms in to speed up a pirouette. Several different factors may be in play, such as glaciers at height melting and the Amazon basin getting drier.

It boggles the mind!

2

If this continues I have a better chance of making it to 100 years old!

3

But the year is staying the same length, it’s just that it may have slightly more days.

4

If the year is taking less time then unless my biological clock speeds up with it, I will live for more of those years.

5

The year is taking the same amount of time - there are just (fractionally) more days per year

6

Wow, I thought maybe there was an easy reference to a … galactic background year or something, but if there is one among the many, many definitions I couldn’t find one. The whole orbit thing has a lot more wobbliness, but it’s much slower than what’s happening to the rotation … or maybe it isn’t, it’s just a smaller fraction of the total … my head hurts now.

7

If the Earth’s spin is accelerating up then the year’s length will have to be reduced to match it. Ergo the year is shorter.

Am I missing something here? (It’s entirely possible)

8

We measure years in days, not the Earth’s position in orbit around the sun.

9

The earth goes around the Sun in about 31,536,000 seconds. For the current length of day that’s 365 days; if the earth’s spin accelerated to twice as fast, there would be 730 days in a year - but the year (which doesn’t depend on the spin of the earth at all) would remain 31,536,000 seconds (or so)

10

Glaciers might have a tiny effect. But the Amazon basin? The mass of that water isn’t gone, it’s just somewhere else. Unless that somewhere is lower than the basin, it would have no effect or the opposite effect.

In a warmer world there is more water vapor in the atmosphere, and the atmosphere itself is taller. Both should have either negligible effect or add to the slowing of the Eatth.

This seems to be a short-term phenomenon (the article mentions that the Earth sped up this year, not over a century or a millenium. So unless you can point to a recent massive change like a glacier breaking off and melting, I don’t think climate change is it.

My guess, based in nothing other than the article: The Earth is an oblate spheroid, not a sphere. And it precesses around its rotational axis, meaning that its angular momentum is going to change as the equatorial bulge moves.

My second guess if that’s wrong os that there has been some land subsidence somewhere, or a shift in mass in the mantle, which is not homogenous but has concentrations of mass. If, say, a lava upwelling subsided under some hotspot it could change the Earth’s angular momentum.

My third guess is that a plausible mechanism for ahort-term changes in angular momentum is a change in the amount of water vapor in the air. So I went looking for info, and found this:

From the paper:

This is a La Niña year, so we should expect slightly drier air, I guess. If the effect was as large as the El Niño effect listed above, that’s 10^15 kg of material taken out of the atmosphere and deposited on the ground. That’s roughly the weight of about a million average icebergs.

So I’ll make that my best guess. It’s a dry year, the atmosphere weighs less and is the thing that sticks out from Earth the most, so it has a lot of angular momentum. It’s lighter this year, so the Earth spins a bit faster.

Again, just a guess.

11

Rotational velocity on its own axis (length of a day) vs orbital velocity about the earth-sun barycenter (length of a year).

It’s not the orbital speed that’s speeding up

12

No, we don’t. That’s why we have leap years and occasionally leap seconds.

13

If the water has moved from the equator closer to the poles it would have the effect of spinning the Earth faster. The radius closer to the poles is smaller, like the proverbial ice-skater tucking her arms inwards. Picture the skater round, like really fat. Now move the arms from the protruding belly to the neck. Spins faster.

14

There are several types of year, some of which are affected by a change in the Earth’s rotation and some not, so this discussion is going to be confused unless everyone clarifies which “year” they are referring to. You are, I think, referring to the calendar year, defined as 365 days. It seems odd to think that the calendar year would remain 31,536,000 seconds if the length of the day changes since the definition is based on days. We currently add leap seconds occasionally and the year changes to adapt to them (that is, a year containing one leap second is one second longer than a year without leap seconds). A calendar year is always 365 days, so changes duration as the day changes and the number of days in the year doesn’t change.

There is also the sidereal year, the time that the Earth takes to complete one orbit with respect to the stars, which is about 31,558,150 seconds. This doesn’t change if the day changes, so the number of days in a sidereal year (currently about 365.2564) changes if the length of the day changes.

There is the anomalistic year, the time it takes for the Earth to move from one perihelion to the next. This is about 31,558,433 seconds and would not be changed by a change in the Earth’s rotation, so again the number of days in the anomalistic year would change.

There is the tropical year, the time it takes for the Sun to move from one vernal equinox to the next. This is the year based on the Earth’s seasons, and is about 31,556,925 seconds, 20 minutes shorter than the sidereal year because of the 26,000 year cycle of the precession of the Earth’s axis. This wouldn’t change if the day changes, so the number of days per tropical year would change.

There is the Julian year, used by astronmers, defined as 31,557,600 seconds (365.25 days). Presumably that definition wouldn’t change if the day changes since it’s already disassociated from the length of day.

There are even more year definitions but these are the most common ones.

15

The presumption is that it’s in the ocean, which is indeed lower than the Amazon basin. And I have no idea why you went for “I don’t think climate change is it” based on my post. Especially since that’s why glaciers are melting.

If you want to disparage speculation by actual researchers in the field and substitute your own, be my guest. I’m not going to try to second guess tentative hypotheses on a topic where the verdict is definitely not in.

It is, by the way a long term downwards trend. The article I first read was in Norwegian, so I picked a non-paywalled one that showed most of the same stuff. I’m currently only finding graphs that end earlier, but the overall trendline in later data also points down.

16

Precession takes well over twenty thousand years to complete a full cycle, which amounts to about 50arc-secs a year, so that is probably not it.

17

I actually meant that I do 't think it’s climate change because of the time scale, which the article sounded like something had changed on the scale of years, not decades or centuries. Climate change just seemed too slow to account for it. And also,

And I didn’t see any real speculation in the linked paper, but it’s gated and I could only read the abstract. In any event, a warmer world has less ice at the poles, more water in the oceans and more water in the atmosphere. The atmosphere also gets taller. I would think all those trends would slow the Earth, not speed it up.

Your other points are well taken.

Yeah. I was totally thinking of magnetic variation when I was thinking of time scales, even though I know better. And even magnetic variation is likely too slow, even if it could have an effect. Like I said, I was just guessing.

As for my water vapor theory, it would be interesting to do the calculation for the difference in angular momentum between the Earth with a drier atmosphere and one with 10^15 kg of extra water vapor in it. I suppose I could do it to see if it’s even feasibly in the ballpark, but an accurate number would involve integrating over the height of the atmosphere, making assumptions anout where the mass of water vapor is in the atmosphere, where the water came from, yada yada. But a simple calc would at least tell me if it was possible at all. Maybe I’ll do it later.

18

You gotta accept that we have come some way since Eppur si muove (be the attribution apocryhal or not) got you hauled before the Inquisition.

19

At noon tomorrow, let’s all face East and fart at the same time. Then we can all knock off work a few nanoseconds early.

20

Apologies everyone, my big brain fart conflated days with years somehow. Okay I’m back with it now.

thanks for showing patience with my inferior deductive reasoning.