13 ms·

Earth sets new record for shortest day

71 points by swamp40 4y ago

h2odragon 4y ago
From the added momentum from various historical figures whirling in their graves. See now if we'd paid a bit more attention to orienting them properly (not too late now!) we could use that angular momentum to straighten the earth's axis and thereby eliminate the scourge of winter! Or at least banish it to the benighted polar lands where it belongs.
- smm11 4y ago
  Or at least orient things so southern areas are lighter, later at night, than northern areas, during the summertime. You know, since the sun is in the southern sky then ...
- dexwiz 4y ago
  http://dresdencodak.com/2010/06/03/dark-science-01/ http://dresdencodak.com/2010/06/03/dark-science-01/
- alchemist1e9 4y ago
  Speak for yourself. I can’t stand the summer. It’s the worst.
  - cyberpunk 4y ago
    wasps, mosquitos, too hot to cycle and no snowboarding? I'll pass too ;)
    - NeoTar 4y ago
      Or move to somewhere in the new world where it is perpetual winter and enjoying those things all year round?
zeeb 4y ago
Well done, everyone!
corentin88 4y ago
> A negative leap second would mean that our clocks skip one second, which could potentially create problems for IT systems. At least biggest cloud providers have already envisioned this [1]. > A negative leap second, if one were ever to occur, would be smeared by speeding up clocks over the 86,399 SI seconds from noon to noon. [1] https://developers.google.com/time/smear?hl=en https://developers.google.com/time/smear?hl=en
- LeoPanthera 4y ago
  Why is a leap smear necessary for skipping forwards? Unlike a typical leap second, which goes backwards, a forward jump doesn't repeat timestamps. The clock could literally just jump forwards a second and it would be fine.
  - bpodgursky 4y ago
    This breaks down when you think of all the code that assumes 60 seconds in a minute: ONE_HOUR_AGO = 60*60 Apply that to the wrong hour and... oops.
    - LeoPanthera 4y ago
      Ah, so this is another "Falsehoods programmers believe about time" situation. https://gist.github.com/timvisee/fcda9bbdff88d45cc9061606b4b923ca https://gist.github.com/timvisee/fcda9bbdff88d45cc9061606b4b...
      - Dylan16807 4y ago
        I wouldn't go as far as "falsehood". Leap seconds aren't inherent to timekeeping. It's easier to do without them, and a system like that isn't wrong.
        LeoPanthera 4y ago
        > Leap seconds aren't inherent to timekeeping. Leap seconds are inherent to timekeeping based on the sun, which all civil time is. Without them, "midday" and "midnight" become undefined.
NDizzle 4y ago
xwdv 4y ago
Could speeding the earth by some significant amount improve cooling performance? Sun rays spend less time hitting one area?
- srcreigh 4y ago
  This reminds me of a video which answers the question "Is it Better to Walk or Run in the Rain?" https://www.youtube.com/watch?v=3MqYE2UuN24 https://www.youtube.com/watch?v=3MqYE2UuN24
  - nomel 4y ago
    But much easier to model, if you assume a first order newton cooling curve.
- thehappypm 4y ago
  This is an interesting question. The emission of radiation is proportional to the absolute temperature to the fourth power. So, the hotter something gets the faster it radiates energy out. Its nonlinear so theres definitely some winning strategy. Energy in is constant, but energy out could vary. I think the way to maximize the energy leaving the planet is to not rotate at all. The energy input would be concentrated and you would have one side very hot — and the hot side would dump the most energy back into space.
- nomel 4y ago
  I think shading the earth is infinitely more achievable.
twawaaay 4y ago
Lack of understanding of the relation between 24 hours and rotational period of Earth. Earth does not take anywhere close to 24 hours to complete a rotation, regardless of how you measure it. Earth rotates in 23h 56m 4s with relation to distant stars. Earth rotates in 24h +- 30s with relation to Sun. The length of day depends on how far Earth is from the Sun, the speed at which Earth rotates the Sun changes throughout the orbit. And so every day the Sun makes a different distance around Earth (as seen from Earth), making the day a little bit longer or shorter.
- kingkawn 4y ago
  23h56m4s doesn’t come in at “anywhere close?”
  - twawaaay 4y ago
    They are talking about 1ms diff from 24h as being a lot. 4 minutes is hundreds of thousands larger difference.
  - dariusj18 4y ago
    No, that's super far off astronomically speaking.
    - kingkawn 4y ago
      - deleted 4y ago
        [deleted]
      - twawaaay 4y ago
        Science is based on measurements and metrology is essentially pedantry, so... a compliment? (And I am aware this is bad logic.)
        4y ago
quench 4y ago
Surprised by this error from time and date .com the earth does not rotate once every 24H of course, that's the time it takes for the sun to be back in the same position (mean solar day) the earth rotates once every sidereal day 23h 56m 4s (minus the 1.55ns)
- sebzim4500 4y ago
  It's not even the time until the sun returns to the same position in the sky, since the earth's orbit is not a circle.
- NotYourLawyer 4y ago
  Yep, this is because the earth spins the same direction as its rotation around the sun. So each year, there’s a discrepancy of one day. And 24 hours / 365 = about 3.9 minutes of discrepancy per day.
- gmiller123456 4y ago
  I picked up on that too. I generally expect that type of simplification in non-technical articles geared toward the general public. But this one was specific enough that I think it deserved a mention.
fanf2 4y ago
The short-term length-of-day chart is very noisy, and has some seasonal components as well. The IERS Bulletin A has a table of DUT1 values for the next year, plus a formula for longer-term projections. (LoD is the rate of change of DUT1.) If you ignore the seasonal components, it is a simple linear formula, multiplying the Julian day number by a LoD factor. Last time I looked this longer-term LoD factor was 320μs short of 24 hours, which suggests the next leap second will be in about 5 years time (2027) and will be a negative leap second. There was a short period towards the start of this year when it looked like the LoD was increasing, but that was only temporary. The decrease in LoD has been fairly consistent (apart from the occasional pause like earlier this year) for a few years, starting when the LoD was more like 1ms slower than 24h, so it was a while before the wider time-keeping community realised something weird is happening. I am collecting various links and notes and bits of code on this and related topics at https://dotat.at/writing/time.html https://dotat.at/writing/time.html
mkl 4y ago
Geologically and astronomically speaking, this is actually one of Earth's longest ever days. Earth's rotation has been slowing down for billions of years as it loses angular momentum to the moon. See e.g. https://www.scientificamerican.com/article/earth-rotation-summer-solstice/ https://www.scientificamerican.com/article/earth-rotation-su..., http://www.iea.usp.br/en/news/when-a-day-lasted-only-four-hours http://www.iea.usp.br/en/news/when-a-day-lasted-only-four-ho....
deleted 4y ago
[deleted]

71 points by swamp40 4y ago

From the added momentum from various historical figures whirling in their graves. See now if we'd paid a bit more attention to orienting them properly (not too late now!) we could use that angular momentum to straighten the earth's axis and thereby eliminate the scourge of winter! Or at least banish it to the benighted polar lands where it belongs.

smm11 4y ago
Or at least orient things so southern areas are lighter, later at night, than northern areas, during the summertime. You know, since the sun is in the southern sky then ...
dexwiz 4y ago
http://dresdencodak.com/2010/06/03/dark-science-01/ http://dresdencodak.com/2010/06/03/dark-science-01/
alchemist1e9 4y ago
Speak for yourself. I can’t stand the summer. It’s the worst.
- cyberpunk 4y ago
  wasps, mosquitos, too hot to cycle and no snowboarding? I'll pass too ;)
  - NeoTar 4y ago
    Or move to somewhere in the new world where it is perpetual winter and enjoying those things all year round?

zeeb 4y ago

Well done, everyone!

corentin88 4y ago

> A negative leap second would mean that our clocks skip one second, which could potentially create problems for IT systems. At least biggest cloud providers have already envisioned this [1]. > A negative leap second, if one were ever to occur, would be smeared by speeding up clocks over the 86,399 SI seconds from noon to noon. [1] https://developers.google.com/time/smear?hl=en https://developers.google.com/time/smear?hl=en

LeoPanthera 4y ago
Why is a leap smear necessary for skipping forwards? Unlike a typical leap second, which goes backwards, a forward jump doesn't repeat timestamps. The clock could literally just jump forwards a second and it would be fine.
- bpodgursky 4y ago
  This breaks down when you think of all the code that assumes 60 seconds in a minute: ONE_HOUR_AGO = 60*60 Apply that to the wrong hour and... oops.
  - LeoPanthera 4y ago
    Ah, so this is another "Falsehoods programmers believe about time" situation. https://gist.github.com/timvisee/fcda9bbdff88d45cc9061606b4b923ca https://gist.github.com/timvisee/fcda9bbdff88d45cc9061606b4b...
    - Dylan16807 4y ago
      I wouldn't go as far as "falsehood". Leap seconds aren't inherent to timekeeping. It's easier to do without them, and a system like that isn't wrong.
      - LeoPanthera 4y ago
        > Leap seconds aren't inherent to timekeeping. Leap seconds are inherent to timekeeping based on the sun, which all civil time is. Without them, "midday" and "midnight" become undefined.

NDizzle 4y ago

xwdv 4y ago

Could speeding the earth by some significant amount improve cooling performance? Sun rays spend less time hitting one area?

srcreigh 4y ago
This reminds me of a video which answers the question "Is it Better to Walk or Run in the Rain?" https://www.youtube.com/watch?v=3MqYE2UuN24 https://www.youtube.com/watch?v=3MqYE2UuN24
- nomel 4y ago
  But much easier to model, if you assume a first order newton cooling curve.
thehappypm 4y ago
This is an interesting question. The emission of radiation is proportional to the absolute temperature to the fourth power. So, the hotter something gets the faster it radiates energy out. Its nonlinear so theres definitely some winning strategy. Energy in is constant, but energy out could vary. I think the way to maximize the energy leaving the planet is to not rotate at all. The energy input would be concentrated and you would have one side very hot — and the hot side would dump the most energy back into space.
nomel 4y ago
I think shading the earth is infinitely more achievable.

twawaaay 4y ago

Lack of understanding of the relation between 24 hours and rotational period of Earth. Earth does not take anywhere close to 24 hours to complete a rotation, regardless of how you measure it. Earth rotates in 23h 56m 4s with relation to distant stars. Earth rotates in 24h +- 30s with relation to Sun. The length of day depends on how far Earth is from the Sun, the speed at which Earth rotates the Sun changes throughout the orbit. And so every day the Sun makes a different distance around Earth (as seen from Earth), making the day a little bit longer or shorter.

kingkawn 4y ago
23h56m4s doesn’t come in at “anywhere close?”
- twawaaay 4y ago
  They are talking about 1ms diff from 24h as being a lot. 4 minutes is hundreds of thousands larger difference.
- dariusj18 4y ago
  No, that's super far off astronomically speaking.
  - kingkawn 4y ago
    - deleted 4y ago
      [deleted]
    - twawaaay 4y ago
      Science is based on measurements and metrology is essentially pedantry, so... a compliment? (And I am aware this is bad logic.)
      - 4y ago

quench 4y ago

Surprised by this error from time and date .com the earth does not rotate once every 24H of course, that's the time it takes for the sun to be back in the same position (mean solar day) the earth rotates once every sidereal day 23h 56m 4s (minus the 1.55ns)

sebzim4500 4y ago
It's not even the time until the sun returns to the same position in the sky, since the earth's orbit is not a circle.
NotYourLawyer 4y ago
Yep, this is because the earth spins the same direction as its rotation around the sun. So each year, there’s a discrepancy of one day. And 24 hours / 365 = about 3.9 minutes of discrepancy per day.
gmiller123456 4y ago
I picked up on that too. I generally expect that type of simplification in non-technical articles geared toward the general public. But this one was specific enough that I think it deserved a mention.

fanf2 4y ago

The short-term length-of-day chart is very noisy, and has some seasonal components as well. The IERS Bulletin A has a table of DUT1 values for the next year, plus a formula for longer-term projections. (LoD is the rate of change of DUT1.) If you ignore the seasonal components, it is a simple linear formula, multiplying the Julian day number by a LoD factor. Last time I looked this longer-term LoD factor was 320μs short of 24 hours, which suggests the next leap second will be in about 5 years time (2027) and will be a negative leap second. There was a short period towards the start of this year when it looked like the LoD was increasing, but that was only temporary. The decrease in LoD has been fairly consistent (apart from the occasional pause like earlier this year) for a few years, starting when the LoD was more like 1ms slower than 24h, so it was a while before the wider time-keeping community realised something weird is happening. I am collecting various links and notes and bits of code on this and related topics at https://dotat.at/writing/time.html https://dotat.at/writing/time.html

mkl 4y ago

Geologically and astronomically speaking, this is actually one of Earth's longest ever days. Earth's rotation has been slowing down for billions of years as it loses angular momentum to the moon. See e.g. https://www.scientificamerican.com/article/earth-rotation-summer-solstice/ https://www.scientificamerican.com/article/earth-rotation-su..., http://www.iea.usp.br/en/news/when-a-day-lasted-only-four-hours http://www.iea.usp.br/en/news/when-a-day-lasted-only-four-ho....

deleted 4y ago

[deleted]