9 ms·
The Earth has been spinning faster lately
- ProAm 6y agoA negative leap-second will be crazy interesting given how the first few leap seconds in computing caused a little havoc.
- BitwiseFool 6y agoWoudln't it be easier to just "let it ride" and the next time a leap second is due, just not add it?
- throwaway894345 6y agoIt's interesting to think about the ramifications of decoupling our measurement of time from the earth's position in the solar system. For example, when we read that something happened around 11 AM, we know that it's probably daylight time, but if we allow for drift, then we can't make that assumption anymore for certain timescales. If the error is small, we can probably deal with it the same way most people understand that dollars in 1950 don't have the same value as dollars today.
- Archelaos 6y agoGPS time is like this. See: https://en.wikipedia.org/wiki/Global_Positioning_System#Timekeeping https://en.wikipedia.org/wiki/Global_Positioning_System#Time...
- wcoenen 6y agoNote that we don't sync to the Earth's position in the solar system (sidereal year), but to the seasons (tropical year).
- myself248 6y agoUnless you're within a few feet of the longitude of the center of the timezone, this is already the case. That ship sailed, back in the railroad era when we decided to standardize time away from mean solar time. If we assume that the Gregorian calendar remains in use for as long as it's already been in use, the total accumulated error would likely be on the order of minutes. We could use a monotonic time scale like TAI for literally centuries and nobody would notice except astronomers, and arguably it would simplify astronomical corrections too because the underlying scale would be monotonic, which it isn't presently.
- klodolph 6y ago> That ship sailed, back in the railroad era when we decided to standardize time away from mean solar time. I’ll make the case here that we still use mean solar time, we just quantize it and push it around for political reasons. In any case, using time zones just means that your clock is off by maybe a half hour or 45 minutes in the lower US, and given the natural variation for sunrise and sunset, that doesn’t seem like an outrageous amount of error for temperate latitudes. Granted, there are a few places in the world with larger differences, like Spain or western China, or Argentina for some reason. Changes in the period of the Earth’s rotation have been estimated based on records of eclipses from as far back as the 8th century, which show that the Earth’s rotational speed is slowing down. Trying to extrapolate from fifty years of atomic time is going to give you the “on the order of minutes” estimate which is likely wrong. If you are trying to work out the error over five centuries, you should probably be using the best available data, which is records of eclipses and ephemerides.
- kevin_thibedeau 6y agoIt's more than 45 minutes on the western extremes in the EST, CST, and MST zones.
- klodolph 6y agoI chose the wording “maybe a half hour or 45 minutes” to make it crystal-clear that the exact number was not relevant to the argument, in a vain effort to avoid responses like this one. Perhaps I should be more explicitly vague in the future. HN is tiring.
- danaliv 6y agoNo, you’re absolutely right. As someone who uses UTC professionally in aerospace ops, trust me when I say your clock is still definitely tied to solar time even if it’s “off” by whatever. Try using UTC exclusively—I don’t just mean on your servers, I mean in every single aspect of your life—and you’ll see what I mean.
- deleted 6y ago
- zokier 6y agoYou are assuming that timezones wouldn't change if the difference would be great enough to notice, something that I don't see any reason to assume.
- anigbrowl 6y agoSuppose for argument's sake that this year produces shorter days, and the trend continues.
- tantalor 6y agoA negative leap second would suppress second 23:59:59 of the last day of a chosen month so that second 23:59:58 of that date would be followed immediately by second 00:00:00 of the following date. Since the introduction of leap seconds, the mean solar day has outpaced atomic time only for very brief periods and has not triggered a negative leap second. https://en.wikipedia.org/wiki/Leap_second#Process https://en.wikipedia.org/wiki/Leap_second#Process
- layer8 6y agoJust a quick reminder that this is in UTC. The missing second will be at varying times of day depending on time zone.
- Avamander 6y agoSounds worth it to me honestly, sets a precedent that it's possible and it's harder to ignore the possibility in future software.
- Ericson2314 6y agoI don't think positive or negative makes much difference. Whether we speed up or slow down we can still "make it monotonic".
- toast0 6y agoA removed leap-second is gobs easier to handle. I can't say if it will or won't be handled properly, because I never tested it, but roughly you have three options: a) software ignores it, and your clock is a second behind as of the discontinuity, and adjusts eventually b) software handles it properly and jumps ahead c) software handles it by explicitly dithering the difference over a day d) c, but it also jumps ahead at the discontinuity e) your network has a mix of b, c, and d, resulting in wonky clocks throughout the day, but generally still +/- 1 second of real time. This could be problematic for forensics, or for distributed software that uses time as measured on nodes to determine order of operations, but using time as measured on nodes requires constant vigilence to ensure clocks are in sync enough. An added leap second is a lot trickier because at least Linux and FreeBSD simply repeat the last second of the minute at the discontinuity if you don't take special action to dither it. That brings two new problems: a) real time is no longer monotonic b) a logic error can result in repeating that second forever
- omgwtfbyobbq 6y agoThe GHG/snow angle is really smart. I initially thought that petroleum extraction/carbon emissions would slow the planet ever so slightly because we're taking stuff from underground and moving it into the atmosphere. But water/ice are much heavier, and reducing the range of elevations where snow is trapped would do the opposite (less water at higher elevations and more at lower), plus there's way more snow/water than petroleum.
- anigbrowl 6y agoIf it is validated perhaps advocates for change will be able to make the argument that we are literally running out of time and it will prove sufficiently engaging that 'skeptics' lose traction in trying and failing to refute it. I use scare quotes because many self-styled climate skeptics are not sincere inquirers after truth but rather shills for established economic interests.
- abeppu 6y agoOr perhaps the established economic interests will astroturf some fear about pumped-water hydro systems.
- zarq 6y agoPetroleum and gasses should be lighter than the rock surrounding them right, so if you move those up, the rock above those layers will be moved closer to the earth's center. So I would expect that that will cause the earth to spin faster, not slower.
- omgwtfbyobbq 6y agoThat's a good point, so it could be both. I'm not sure how high the average distribution of CO2 would have to be to offset that. The petroleum/gas could also be compressed under pressure, which might offset that effect to some degree.
- adamjb 6y agoBack of the envelope calculation: a 1 ms/day slowing would require ~10^20 kg of mass at the equator to be moved a km inward. For scale, wiki helpfully points out that the world's oceans weighs 10^21 kg. https://www.wolframalpha.com/input/?i=rotational+angular+momentum+of+earth+*+1ms%2Fday+*+1%2F1km+*++1%2F%28465.10+m%2Fs%29 https://www.wolframalpha.com/input/?i=rotational+angular+mom... https://en.wikipedia.org/wiki/Orders_of_magnitude_(mass)#1018_to_1023_kg https://en.wikipedia.org/wiki/Orders_of_magnitude_(mass)#101...
- anigbrowl 6y agoI love the idea of switching to atomic time. Using a different paradigm to conceptualize it could lead all sorts of whimsical new approaches to representing it, and where whimsy wanders new insights and discoveries often ensue.
- layer8 6y agoOn the one hand I agree. On the other hand the discrepancy to solar time is growing quadratically due to tidal friction of the earth with the moon, which is prone to create interesting issues some centuries down the line.
- swebs 6y agoBy then, hopefully civilization won't be bound to just the Earth.
- rohan1024 6y agoAnd adopted the decimal calendar[0] which hopefully has fixed all the issues with current calendar. [0] https://medium.com/@duspom/proposal-for-a-base-10-calendar-b385071a219d https://medium.com/@duspom/proposal-for-a-base-10-calendar-b...
- ljm 6y ago> I believe this would be more than outweighed by the increased productivity of fewer weekends and longer periods of contiguous work between them. I don't think that's how productivity works
- Gibbon1 6y agoAs a peon I measure my productivity by the ratio of my free time to the actual work I do.
- zokier 6y agoThe projections I've seen estimate that the drift would reach about 1 hour in a millenia (i.e. around year 3000), ± few centuries. And I don't even know if 1 hour difference really would be that significant, these days already some regions have their local time differ from solar time by over an hour (e.g. Argentina, Spain, large parts of China) because of timezone shenanigans.
- jedberg 6y agoI don't think a negative leap second would cause much of an issue at all. The reason a positive leap second was such a problem was because it add an "invalid entry", ie. 23:59:60. But a negative leap second would just be skipping a valid entry, which happens all the time if you're using NTP to set your clock. Sure, date math libraries would need to updated, but they already got updated for the positive leap second to have tables they can look up to find out which seconds to add, so adding an entry for a skip isn't much different. Most of the havoc of the positive leap second was in time series data having that invalid entry. That won't happen with a negative leap second. There just won't be a value there.
- segfaultbuserr 6y ago> I don't think a negative leap second would cause much of an issue at all. But nobody has tested it in the wild. It's entirely possible to trigger an existing bug in the code base. I expect some disruption from the first negative leap second event. After that everything would probably be gradually stabilized.
- jedberg 6y agoIt's constantly tested in the wild. Every time your computer does an NTP update and has to jump ahead one second or more, you've just tested it.
- segfaultbuserr 6y ago> Every time your computer does an NTP update and has to jump ahead one second PCs don't run anything crucial, usually you can set your clock to 2001 without visible problems, the same is not true for a server. A server uses ntpd, not a bruce-force ntpdate. Under ordinary conditions, ntpd adjusts the clock in small steps so that the timescale is effectively continuous and without discontinuities. But I think a negative leap second is quite violent.
- jedberg 6y ago
- bioinformatics 6y agoI think it's global warming. It has to be.
- samatman 6y agoIt could be but it absolutely doesn't have to be. Heavier material in the mantle subsiding towards the core could do it just as easily, and there is a lot more mass beneath the crust than above it.
- jandrese 6y agoI would expect global warming to have the opposite effect. Slightly expanding the atmosphere causing the mass to be further from the center, slowing down the rotation. The problem is that the atmosphere is so light compared to the rest of the earth that even at the nanosecond level I have doubts you would see this effect. To affect the rotation of the Earth by whole seconds/year you need to be talking about yottatons of rock shifting.
- _trampeltier 6y agoI have a different idea, it could be the global warming. A lot of snow and ice melt and flow down from the mountains in to the ocean. So a lot of mass does come a bit closer to the center and would it make it more fast. And wasn't lately not also something with the magnetic field?
- epistasis 6y agoArticle speculated differently: > They also have begun wondering if global warming might push the Earth to spin faster as the snow caps and high-altitude snows begin disappearing.
- temptemptemp111 6y agoAmazing what supposedly smart people will believe.
- lkxijlewlf 6y agoMaybe it brought its arms in closer.
- jedberg 6y agoBasically yes. They're saying snow melting is a big cause, because it brings that heavy water weight down closer, along with erosion and the mountains bringing dirt down closer to the center.
- beezle 6y agoThe environment of and around the earth is pretty chaotic. Think it is way to soon to postulate what caused such a tiny variation. How to account for it, different subject. Odd that I read this first a few days ago via a link to a Martha Steward website lol
- epicureanideal 6y agoElon Musk is cackling in his lair. "Mwahahahaha! It works, it works!" His assistant types onto their tablet... Test of MegaRaptor Engine successful.
- quijoteuniv 6y agoMust be because the earth is flat now
- feralimal 6y agoWhy would the earth speed up? Are we going downhill?
- spuz 6y agoIf the average mass of the earth moves from high to low elevation then the rotation of the earth will increase in order to preserve angular momentum. It's the same physics as an ice skater who spins faster when they move their arms close to their body.
- amelius 6y agoThat's one reason. Another reason could be that the Earth is not symmetric and the Moon is pulling it in some strange way. Or perhaps some people have installed lots of flywheel energy storage units [1] somewhere, all spinning in one direction. [1] https://en.wikipedia.org/wiki/Flywheel_energy_storage https://en.wikipedia.org/wiki/Flywheel_energy_storage
- fuzzfactor 6y agoIf everybody puts on their running shoes and heads west fast enough that might be able to do it. I've commented about going downhill in unrelated messages where the vast majority is not trying to move anything but up.
- deleted 6y ago[deleted]
- burlesona 6y agoI love this quote: > Scientists also noted that this past summer, on July 19, the shortest day ever was recorded—it was 1.4602 milliseconds shorter than the standard. It’s so interesting to think about (a) how incredibly stable the rotation of the earth in in human terms, and also (b) how far we’ve come to be able to measure something so vast (the rotation of our planet) against a scale so tiny (milliseconds - shorter than an blink). The world is amazing :)
- simonh 6y agoAtomoc clocks are nuts accurate nowadays. They’re so good you can measure the relativistic gravitational time dilation effect of a height difference of a few inches. It takes a while, like about a year I think, but you can do it.
- Technically 6y agoPeople talk about rockets and computers, but to me atomic clocks are the pinnacle of human achievement. So many other technologies are built off of accurate time measurement, and it's a very clever mechanism (at least the one in Boulder is that I'm aware of). The semiconductor is pretty good, too, but not nearly as clever.
- dralley 6y agoA significant amount of the "cleverness" is in how semiconductors get made rather than the transistors themselves.
- Technically 6y agoYes, I meant this more about my appreciation of the clock rather than my ignorance of semiconductors and rockets, which I can assure you is massive.
- dredmorbius 6y agoPrecision is a phenomenal enabling technology of itself. In time, space, energy, matter (purity, dimensions), etc.
- Tommah 6y agoIt's trying to throw us off it.
- tengbretson 6y agoThis is concerning news.
- anonu 6y agoI'm not sure why computer scientists really care. Call me a naysayer if you like: but why can't we just ignore this problem? Time as we think of it in computers is an overlay over time in the physical world. If they're off by a millisecond will anyone notice? I was a high frequency trader for a long time. The only thing that matters in time world is that computers agree on the same time. Not that computer time is aligned with real world time.
- amelius 6y agoYes. The only ones who will notice the difference are the astronomers, who created the problem in the first place (unless the time-difference becomes so big that it starts affecting perceived daylight times). On the other hand, it would be great if some authority could release a package with time conversion routines that everybody could include in their software projects and be done with it. However, every language needs its own implementation, which is a problem created/not fixed by IT people.
- shultays 6y agoI wonder how we define a "day" and when do decide it is next day now. Earth rotates/wiggles all the time and it is far from a perfect sphere or any shape. And it changes its shape as well How can we decide on such small time scales it is no longer the same day when there are so many variables.
- malwarebytess 6y agoObligatory Earth did us a solid and ended 2020 early in unprecedented fashion. Can anyone speak to the problems regarding "true time?"