3 ms·
Since that was published, the earth has been slowing down gradually. I keep a casual eye on IERS Bulletin A, which has the latest earth rotation observations, p
by fanf2 5y ago
Since that was published, the earth has been slowing down gradually. I keep a casual eye on IERS Bulletin A, which has the latest earth rotation observations, predictions for the next year, and a simple formula for longer-term estimates. https://www.iers.org/IERS/EN/Publications/Bulletins/bulletins.html https://www.iers.org/IERS/EN/Publications/Bulletins/bulletin...
The line I look at is
UT1-UTC = -0.1204 + 0.00020 (MJD - 59593) - (UT2-UT1)
which gives the current value of UT1-UTC (if -0.1204 grows to more than about +0.5 then we need a negative leap second) and the estimated long-term difference between earth’s rotation and 24x60x60 seconds (0.20 ms fast was up to 0.26 ms fast a few months ago).
Actually, I have some code that looks at Bulletin A for me, https://github.com/fanf2/bulletin-a https://github.com/fanf2/bulletin-a which until recently was estimating that the next leap second would be a negative leap second in about 2028/9. But now its guess is receding into the future past 2030.
I have a few tweet threads on this topic, which you can find via https://twitter.com/fanf/status/1478767806187552776 https://twitter.com/fanf/status/1478767806187552776 with some clicky-clicky to dig the older ones out of twitter’s delightful user interface.
See also https://news.ycombinator.com/item?id=25145870 https://news.ycombinator.com/item?id=25145870 for some previous discussion here on this topic.
So nothing dramatic is likely to happen any time soon, though the current situation is quite weird.
- d0mine 5y agoThere is Python script https://github.com/zed/leap-second-client/ https://github.com/zed/leap-second-client/
- kelnos 5y agoI'm a little confused: if you look at the updated version of the same graph from the article (https://datacenter.iers.org/singlePlot.php?plotname=BulletinA_All-UT1-UTC&id=6 https://datacenter.iers.org/singlePlot.php?plotname=Bulletin...), it shows a continuation of the results of the speeding-up behavior, a positive slope on the UT1-UTC graph. Or am I misinterpreting things?
- fanf2 5y agoI was mostly talking about the slope of those charts: the line is still going upwards, but more slowly. The seasonal effects (the regular lumps) are large so it is hard to tell from the graphs what the long term trend is. My guesses are based on the IERS estimate for what happens after the detailed predictions in Bulletin A, and their charts don’t go that far into the future.
- kelnos 5y agoAhhh, I see. So rotation is still speeding up, but that speeding-up is itself slowing, and your belief is that, before too long, it'll go back to the normal slowing-down state?
- sla29970 5y agoHave a look at the rate of earth rotation over the past 250 years where it is unclear that there is long term acceleration or deceleration. https://www.ucolick.org/~sla/leapsecs/dutc.html https://www.ucolick.org/~sla/leapsecs/dutc.html
- mlyle 5y agoIf it was going the same amount "faster", the slope upwards would be the same. But it's lessened significantly, even if it is still currently heading towards a negative leap second being necessary.