The Leap Second Explained | Space Time | PBS Digital Studios
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Every once in a while we add a second onto our days. Similar to the Leap Year, this is known as the Leap Second. But, if the Leap Year already helps us account for the offset from a calendar in days, what exactly does the Leap Second do? Check out this video for the answer!
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Hosted by Gabe Perez-Giz
Made by Kornhaber Brown (www.kornhaberbrown.com)
Who here from Usogui bro
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We're beating the leader of kakerou with this one.
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Usogui got me here
We taking over kakerou with this one
Holy crap! I didn't imagine it was so complicated to keep track of time for our daily usage thanks for enlightening me
"I told you, i'd make a comeback"
Baku Madarame is like:
Still feeling thrilled?
You're a liar arent you
MY ONLY QUESTION FOR YOU IS WHY IS YOUR THEME SONG SO CATCHY I COULD LISTEN TO IT ALL DAY
Mattia m I know, right?!? I break out into the theme song all the time now. It's infectious.
Baku:i command time myself
I remember seeing a graph on leap seconds with the mouseover text "a graph documenting the war between timekeepers and time."
Awesome, thanks for this! Makes perfect sense now.
Thanks for the informative video! I did not understand a word 😊
Thank you for explaining this CORRECTLY! Every other article on the matter says leap seconds are needed because the earth is slowing down. This is WRONG. Even if the earth stopped slowing down right now, we would still have to add leap seconds at the rate of 1 every 1.5 yrs, because the way the second was defined in 1967.
The best explanation I found.
I think the fact that we are able to measure the earth's rotation around the sun with such accuracy is amazing, how is that done?
Rotation means around the Earth's own axis. The Earth revolves, not rotates, around the sun.
@@HebaruSan The Earth revolves AND rotates, around the sun. In other words, two motions at the same time.
@@johnnicholson8811 That is true, but "around the sun" only makes sense for one of those motions.
@@HebaruSan en.wikipedia.org/wiki/Sidereal_time
Can you make a video or two about interstellar exploration?
I love this channel. It's free of political bullshit and is nothing but objective hypotheses, theories, and law.
eh... 'scuse me maam. Just one question before I go... Why doesn't the scientific community just re-calibrate the earth-second to match the current state of Earth's rotation and spin instead of inserting leap-seconds to accommodate a two-centuries out-of-date calculation? And therein save Google from having to invent the leap smear?
If I understood the video (I may very well have not), then it sounds like a lot of very smart people have done a lot of very hard work to accommodate a problem that only exists in an imagined disparity between semi-arbitrary definitions of something that is presently measurably different than the figures in use; and that we have no plausible reason to continue using. Am I missing something or are we applying duct tape solutions when we've got replacement parts in the truck?
Presuming I'm not just really confused, it raises a fun question: If we re-calibrate the earth-second to match the current spin and rotation of the Earth around the Sun, how many years would it be before we'd need our next leap-second, or better yet, a leap-second coupled with another re-calibration? I mean, if you're going to bother everyone with a leap-second, you might as well fix the broken timebase too.
Earthquakes and eruptions change the speed of the Earth marginally, which cannot be predicted to have a constant "time" reference.
So then we're at a 200 year out of date data set on earth's spin + earthquakes and eruptions. Why not recalculate the baseline for the state of spin as it exists now instead of using old values? And when, in a hundred years or two we need another leap second; take the opportunity to recalculate again so we won't need a leap second every other decade.
But, like I said, maybe I misunderstand entirely.
+roninpawn I could be wrong, but it might not be possible due to explosions, earthquakes and volcanic eruptions. Nuclear explosions also offset "time", along with impacts of any size, mass leaving the planet, etc. Again, I could be wrong.
I blame North Korea.
+roninpawn I'm guessing it's easier to add in leap seconds than it is to re-calibrate every equation ever, scientists don't want a floating definition of a fundamental unit.
This video made me wanna drop my handkerchief 1 second longer
Loving the series!
I just finished reading the illustrated Brief History of Time and am on to Universe in a Nutshell; i'm wondering if anyone here could recommend subsequent books I should check out that maintain an accessible-yet-not-too-diluted tone for explaining some hefty physics concepts to a layperson. Thanks!
For this video all you had to say was "Its a timey-wimey thing".
After watching this video several times I still don't understand the reason for such frequent leap seconds in the past 40 years.
Hier00 essentially, the official international definition of a second is wrong in respect to the rotation of the Earth. Forget for a moment about how the Earth's rotation slows down in geological scales, that is irrelevant for this matter. Instead, think about how we have leap days on February every 4 years. Why do we have those? It is because our calendars are "wrong" in respect to the actual time it takes the Earth to orbit the Sun, and thus, in order to correct that discrepancy, we add an extra day now and then. The exact same thing happens with seconds, only we add them after many more years as the difference is smaller.
Arturo Gutierrez That doesn't answer the question though. Gabe in the video said the math doesn't add up (and it doesn't), and then goes on to talk about how our second measurement has been consistent for the past 200 years. Still confused.
Hier00 our second measurement has been consistent, but to the same error. The mistake has been inherited from technology to technology and the current international definition of a second is off from the actual duration of a day, just like the days on a calendar.
Basically, people screwed up in the past, and because of that, leap seconds must be added to correct it. What Gabe was talking about when he spoke of the math not adding up was for those who tried to reason that leap seconds were due to the Earth's rotation slowing down, which is not the case.
Arturo Gutierrez Well, your explanation made no sense whatsoever (technology? people screwed up?), but you did put me on the right track. Of course it's due to the Earth's rotation slowing down; it's the cumulative discrepancy between the anchored SI second and the 1000 year old fraction. Thanks for the responses!
Hier00 In 1967, the modern SI definition was established (it's defined as some number of transitions of an electron in a cesium atom from one state to another, but that's beside the point right now). Suppose that, in 1967, the SI definition had been calibrated to be exactly 1/86,400 of a day in 1967 (it wasn't, but pretend it had been). In this alternate reality, when would the reading 12:00pm on our clocks first have gone 1 full second out of sync with the Sun being overhead (on an average day at a particular spot on Earth, I mean)? Answer: around the year 51,967. Why? Because a full solar day gets about .002 seconds longer every 100 years. That's 1 second every 50,000 yrs, approximately. So after 50 thousand years, the slowing of Earth's rotation would have necessitated injecting a leap second to let the Sun "catch up".
But the second in 1967 *wasn't* calibrated to be 1/86,400 of a day in 1967. It was calibrated to the ephemeris second, and it turns out that the day was 86,400 ephemeris seconds long back in 1820 or so. So in 1967, the SI second was set to 1/86,400.0025 of a day. Yikes. That means 12pm on our clocks will end up 1 second out of sync with the overhead Sun about 30,000 times sooner than the slowing of Earth's rotation would suggest, or just b/c we set our clock unit in a weird way. In other words, the current leap second is not happening as often as it does b/c Earth is slowing down its spin at some obnoxious rate. It's b/c 24 hrs on our clocks isn't quite 1 full solar day.
For an analogy, imagine you're measuring the distance from Earth to the Moon, which grows by about 3cm a year. You want to make imperial measurements in yards, but all you have is a meterstick, which is close to a yard but about 8.5cm longer. Start laying the meterstick, end over end. After the 100th iteration, you think you've counted out 100 yds, but you've really counted out a little over 109 yds. So you stay in place while you keep counting 101, 102, 103,...., 109 to let the true measurement "catch up" to your flawed measurement, and then at 110 you again start laying the meter stick end over end. Every 100 iterations, you stay in place and add 9 to your count. That's basically what a leap second is -- staying in place b/c we're measuring yards with a meterstick.
I assume the sun would burn Earth before It slowed down enough to matter or else it would have been addressed in the Earth destruction thing? Idk
Good information 👍🏼
Please slow down a bit when you’re talking
You can show down videos on CZcams.
First off, Gabe - you are absolutely brilliant. Now to ask my potentially stupid question:
Has there ever been serious consideration of a base 10 system instead? Perhaps adjust the duration of a second (make it a little shorter) so we have 100 seconds each minute, 100 minutes each hour and 10 hours each day. Computer could assign the exact duration to accurately match orbital rotation periods and do away with all of these adjustments. Odds are I am missing something on why that would be a bad idea.
Johnmichael Monteith The French tried that in 1793. No one liked it so they abandoned the effort in 1805
Dave Olsen So they did. Cool. Thanks! Well, at least the French got their metric system, I suppose. mentalfloss.com/article/32127/decimal-time-how-french-made-10-hour-day
Johnmichael Monteith Some additional info: Back in that day, fractions of degrees angle were also divided into minutes, seconds, thirds... (and often still are). So logarithmic tables for calculation of sines, cosines and so on were, of course, in 360 degrees times 60 minutes times 60 seconds (normally in 1" or 10" steps).
The French introduced the 400 grades, 100 minutes, 100 seconds system, so they did a huge recalculation of logarithmic tables in these units. They were never published, though.
locomat.loria.fr/cadastre/cadastre.html
en.wikipedia.org/wiki/Gaspard_de_Prony
So why not redefine the second again? I'm a little bewildered why they defined the second off an 1820 standard in the first place instead of a 1967 solar day. If my math is right, re-defining a second to be 9,192,632,046 periods of a cesium atom should put an end to needing to insert leap seconds for quite some time.
Dave Olsen I don't know, but I think the answer is that this would require recalibrating almost everything on Earth that has already been calibrated to seconds and, by extension, we'd have to recalibrate everything that's defined in meters, since the meter is defined in terms of the second and the speed of light. Leap seconds seem like the easier solution.
PBS Space Time You're right, the legacy problem is pretty daunting. Since we can't easily fix the mistakes of our predecessors, I'm now of the opinion that we just let it drift for a few decades and then put in a leap minute. Yeah, it'll throw the computer programmers in a tizzy, but it'll only be once every century or so instead of every few years.
It would be easier for software developers that way. Having to deal with those pesky leap seconds every few years is quite annoying.
But I believe that it's important for astronomers to have a good sync between time and star movements. Not adding leap seconds for that much time would result in a significant unsync between time of day and sunrise/sunset and moon phases.
Why is it slowing down?
ooooooh!
good to know :)
Please consider referring to "noon" or "12 noon," and "midnight" or "12 midnight," instead of 12am or 12pm. www.nist.gov/pml/div688/times.cfm . Just for reference, there doesn't seem to be an easy way to find out, as I've done much (Google) searching and reading, but the day would seem to begin (and not end) with midnight.
Earth is slowing down currently, but the standards also allow for removing a leap second. If somehow Earth were to speed up its rotation, and DUT1 therefore grow in the opposite direction to presently, the correction would be removal. But at this point, it would seem unlikely.
Another misconception I have heard in popular media is that a leap second occurs multiple times, like daylight saving time to standard time (or vice-versa) transitions, as in, one per timezone. That's simply not the case; it is inserted (or deleted) once globally, at midnight UTC on either 30-Jun or 31-Dec (so 8pm EDT or 7pm EST for example).
Hopefully we won't have to do leap seconds regularly more than once a year at some point in the future, because that would REALLY suck, particularly for programmers.
I never understood how annoying time could be until I started doing orbit calculations. :l
Anon Smith Word
I split my sides laughing at that comment. Thank you. :)
So we are not effectively going by atomic time. Rather we are messing up or shifting our atomic time to agree with the less accurate solar time?!
so back in the dinosaurs days the day was shorter? cool
Yup, 70 million years ago a day was about 30 minutes shorter.
There are other videos which explain this much more clearly.
gospizana There are also many (in fact, most) videos that explain this *incorrectly*.
Isn't the second defined as the time it takes light to travel 299 792 458 metres in a vacuum?
Rohan Bunsee No. The second is defined as the duration of some large number of a particular electron transition in cesium (see electrocat1's comment above). The meter is then defined as 1/299,792,458 of however far light travels in vacuum in 1 second.
why cant we just find the most steady, stable day of the year and leap second every year?
Each day of the year is about the same length. This has to do with the observed solar day getting slightly longer from century to century.
So why don't we correct that?
I thought the second was defined as every 9192631770 periods of oscillations between the ground state and the most excited state in a cesium 133 atom.
electrocat1 That would be "In 1967 we redefined the second again based on atomic clocks." @ 0:41
somewony ah okay. Thank you.
+jury trial neato
Baku when he realized that he could have just watch this video for 2 minutes and 21 second instead of planning for years.
The Earth slowing down 1 second per year seems a bit much....and doesn’t make sense when taking into account the age of the planet. Can someone explain more on this?
I need a second to think about this .
Your math is alittle off , on purpose or accident? In the last 38 years , it averages out to 3/4 sec per year
i am afraid you are mistaken look for fymen explanation of space time
Feynman's Explanation
So now we have a method to determine a curved geometry.
The problem I find students having with the above example is the misconception that for a flat space to be curved, it then has to be curved into a higher dimension, like our 2D chalkboard curving into a 3D space. Or worse "our 3D space is curved into the 4th dimension which is time" which is wrong on so many levels. Time is curved too, and in fact our Newtonian gravity is basically due to curved time. [1]
So Richard Feynman demonstrates this beautifully by imagining a bug world and measure distances with a metal ruler, as shown:
source: Curved space
Now, imagine a hot spot in this bug world and what might happen if the bugs were to measure out distances as normal. They metal rulers would expand in hotter regions compared to cooler regions and consequently they would find that Euclidean geometry is not valid and they live in a somehow curved space.
Baker Das It's not that I'm mistaken -- it's that we haven't gotten to the "punch line" of curved spacetime and its connection to gravity yet. I will be saying pretty much what you said in this comment in Part 3 of the GR series. The video has been filmed -- it's just in post-production. Only instead of a bug with metal rulers hat are hitting hotspots, our analogy will be an ant using a tape-measure on a sphere. Check it out -- I'll think you'll agree I end up giving a pretty solid explanation of what exactly we mean when we say "curved spacetime = gravity" (including the part about the 'time' part of the metric being responsible for 99.99% of what we call Newtonian gravity). Trust me, you and I are *totally* on the same page :)
How Time would be syncrinasied if it was a flat Disk I think the sun would go under that disk for casting its shadow on the moon and be eclipse shape shadow...
Epic Haxer What? Earths not a flat disk. But muh (insert retarded holy book here) says its so.
I was assuming What If it was a Flat Disk How would the Relativistic time be measured in respect to What is already
He's known as usogui (the lie eater)
there is also a picture which depict the concept more clearly but i couldnt upload
here is the website for any one
www.quora.com/Relativity-physics/How-can-space-time-curvature-be-explained-in-laymans-terms
so the earth spinning is slowing down could we asume it is due to increased total mass of earth is increasing? i mean few centuries ago all the energy that we released from fossile fuels wasnt in the atmosphere
That wouldn't increase the mass of the planet though. The fuel will weigh the same whether or not it's a solid or gas.
yes i agree i phrased that really awkwardly what i ment was a reference from mass=energy/c^2 and thinking that the energy from coal, fossil fuels was since few centuries ago underground, that energy/mass was moved from underground to the atmosphere's temperature increase, altho it is true the total mass/energy of earth shouldn't increase nor decrease the mass/energy was moved radialy and similarly as if a rotating ice skater slows down while moving arms outward earth should slow down
The Earth's rotation is slowing down due to tidal forces exerted by the Moon.
In the very distant future, the Earth will end up in a tidal lock with the Moon, just like the Moon is in a tidal lock with the Earth right now (same face of the Moon always pointing to the Earth).
+ttadgs1 The total mass of the earth is actually DECREASING - there's more gas escaping the atmosphere than dust and debris being swept up as Earth orbits the Sun. SciShow has a video on this: watch?v=5TmNiZNCd-w
ttadgs1 No. completely negligible
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one more time, i didn't quite get you
Through Einstein's work, we discovered that Newton wasn't correct after all.
Now that we have discovered that the speed of light is not constant, should we not question our current understanding of the universe?
+AntiMessiah
Of course! And you can bet scientists are CONSTANTLY questioning any current understanding of anything =P
That's how science works, right?
Haven't you heard about the various models that try to describe the universe? Like the Super Chords Theory and others I don't remember now...
Super Chords Theory? No, will look that up.
Through Einsteins work, we discovered the limitations of Newton's work. Newton's laws are still very much usable for certain tasks in certain problem domains.
What if an intelligent alien species can actually see earth from afar, but the only thing they are seeing is a time before humans and thus, that is why they haven't visited us yet? Mind blown
Hi
Baku watched this video to make his plan
Back when space time was educational
I am more confused
Today -0.5 Mili second
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DelightfulDonut You're cool aint ya
TomNil 337 im the best
the more i think about it the less i get it.
making a relative second seems... dum. i.e. dum stuff happens.
Could you speak mor faster pls, coz all was like whzsjsfhlzsg.
So we are all going to die because of this? Thanks Obama.
No science bro, no watch
agreed. the worst