Time, and our imperfect orbit

2007-01-22

in Geek stuff, Science

In keeping with the dictates of thesis writing, and the sage comments of those who suggest that blog entries are not the best use of time, I resolve the following: posts on this blog between now and the completion of a draft thesis shall be limited to no more than one substantive and one narrative post per day, the latter to generally include a photograph. Posts that pertain directly to the substantive content of the thesis, as designated by the M.Phil Thesis category, are exempt from these restrictions.

An article in Harper’s that I first took up because of its hyperbolic title – “Clash of the Time Lords: Who will own the measure of our days?” – is actually a really interesting demonstration of how human beings try to make the world fit within our understanding.

In particular, the article hinges on the fact that the second has two distinct definitions. The first is based on astronomical phenomena: 1/86,400th of a day, that being 1/365.25th of the time it takes for the Earth to orbit the sun. The second is based on the extremely precise oscillation of cesium atoms, the measuring stick used in atomic clocks. Specifically, it is 9,192,631,770 oscillations. The trouble arises from how those two are not the same; the Earth does not sweep through its orbit with perfect precision. Rather, it wobbles, hits things, and slows down. As such, astronomical time ‘slows down’ as compared with atomic time.

Right now, this is corrected for using occasional leap seconds. Every time the Earth has lagged behind atomic time by one second, one second is added to the reckoning of atomic clocks. Since our orbit continues to slow, leap seconds need to be inserted with ever greater frequency. This is good for astronomers, since it lets them continue to aim their telescopes in the same way as before. What is more controversial is whether this is a sensible system overall.

From a galactic or universal perspective, it doesn’t seem too reasonable. Ultimately, it is a throwback to the era when it was believed that the Earth occupies some metaphysically special place in the universe. When we concede that it is just one of uncountable numbers of things zipping about under the influence of gravity and other forces, the idea that time should be altered to correct for the peculiarities of its orbit becomes a difficult one to maintain, for any reasons aside from the practical ones of astronomers. Consider, for instance, the question of whether it would be appropriate to subtract a period of time if a comet or asteroid impact cause the orbit of the Earth to speed up.

That said, there are a good number of practical reasons to consider fiddling with time to match our orbit. The disjoint between calendar time and astronomical time is the reason for the piecemeal and difficult shift the world has made from the Julian to Gregorian calendars. Indeed, the point was to return key astronomical events, like the equinoxes, to the points in the calendar where they ‘should’ be. That shift famously required the negation of eleven days. For those who followed the decree of Pope Gregory XIII, they were October 5-14th, 1582. People in the UK and US didn’t switch systems until later, erasing September 3-13th, 1752. As such, the measure of time differed be eleven days across the English channel. When the US and UK did make the switch, the passage of calendar time was re-aligned with the experience of astronomical time.

Over thousands of years, allowing atomic time to rule, and diverge to an ever greater extent from astronomical time, would shift the seasons into ever different positions within the calendar. Very slowly, sunrise and sunset times would get out of sync with the times of day when they previously happened: likewise, the solstices and equinoxes. Already, the GPS satellites, which rely critically on super precise time, are 14 seconds ahead of UTC (Coordinated Universal Time). This is because they have not been counting leap seconds. Time in Unix computer systems also ignores leap seconds. As more leap seconds are added to UTC, that gap will grow.

Perhaps this is the most obvious solution: acknowledge the split and come up with two separate accountings of time: one that just counts the oscillations of those cesium atoms and thus the actual number of atomically defined seconds that pass, and another that corrects those figures for the peculiarities of our passage through space. Most people would probably only bother with the latter, but having the former as a kind of absolute record of how much time has passed since event X strikes me as more honest.

PS. Slightly related to the above is this excellent comic about dinosaurs planning to steal the prototype kilogram (the actual hunk of platinumiridium that defines the unit of mass).

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{ 17 comments… read them below or add one }

Brett January 22, 2007 at 11:03 am

I do admire how you manage to blog so consistently and indepth and still manage your busy school schedule…im thinking you dont sleep much or maybe youre just more efficient than me which wouldnt take much…

R.K. January 22, 2007 at 10:36 am

In keeping with the dictates of thesis writing, and the sage comments of those who suggest that blog entries are not the best use of time, I resolve the following: posts on this blog between now and the completion of a draft thesis shall be limited to no more than one substantive and one narrative post per day, the latter to generally include a photograph. Posts that pertain directly to the substantive content of the thesis, as designated by the M.Phil Thesis category, are exempt from these restrictions.

Sounds sensible, though maybe going for straight-up one post a day would be more sensible still.

Milan January 22, 2007 at 3:17 pm

Brett,

What’s about about the efficient use of time? One of the 128 blogs I read regularly is linking one of my favourite Monty Python clips.

tristan January 22, 2007 at 9:38 pm

I like your blog Milan, but your metaphysics are bad. Adjusting clocks and calenders to match the appearences isn’t a “throwback to an era when it was believed that the earth occupies some metaphysically special place in the universe” (although, I don’t see how you could hold the argument that it doesn’t still mantain a metaphysically special place in the universe – it is the only place we know of that has metaphysics, or physics for that matter, which are essentially the same discipline). We adjust calender and clock time to keep our time in tune with appearences, whether they be seasons or precise astronomical calculations. The unit of time is arbitrary and however we measure it, our measurement will be incomplete and it will need adjusting to match the appearences. Do you suggest that we begin a time system that is not connected to the heavens’ relation to earth? On the whole I find your point in this post confusing – what are you arguing that we ought to do instead of leap seconds?

Why would we only bother with a time measuring system that automatically adjusts for the wobbles in our orbit? And isn’t that the opposite of when you say ” Consider, for instance, the question of whether it would be appropriate to subtract a period of time if a comet or asteroid impact cause the orbit of the Earth to speed up.”

As physics has progressed we need to turn absolute measures (like the meter, defined by some relation to the circumference of earth) to arbitrary ones (the meter is now defined by the time it takes light to pass through it, and it doesnt’ take account of the fact that the earth might grown or shrink around the equator). However, since astronomy is the origin of our measurements of time, the absolute measures need to be adjusted to fit with the appearences, something unneccesary when it comes to meters of kilograms.

Why is it more “honest” to use a purely arbitrary system beginning from a purely arbitrary point?

I’m sorry this comment is confusing, but I am confused by this post and so it comes out this way.

Milan January 22, 2007 at 9:42 pm

whydoyourequireanemailwhen@Icanjustusethis.com

See the little “More than 1839 people have failed to spam this blog” notice at the bottom of the page? Part of the system for foiling spam robots depends on email addresses.

Milan January 22, 2007 at 9:46 pm

Tristan,

I wish I could send you the original article, but Harper’s doesn’t put their content online. If you can find the December version, you can read it there.

Sorry if the post is confusing. With regards to the comet impact idea, I am saying that if we correct for Earth’s slowing orbit by adding to atomic time, we would have to subtract time if the orbit was accelerated for some reason.

Time calibrated to Earth’s orbit has a certain validity and a lot of usefulness here, but not for any other place in the universe. Hence, if we do not hold the Earth to be particularly special, non-Earth-corrected time seems the most honest sort, no?

tristan January 23, 2007 at 5:37 am

You’re making a false equivocation between the a)time it is at some point in relation to earth’s movement around the sun and 2)the absolute measure of time. No one is claiming that it has been some perfect round number of minutes and seconds since the beginning of our current time system, nor does anyone claim it to have any corespondant relavence to things happening in other parts of the solar system or galaxy. Time as pure measurement, simple difference, is a magnitude, whereas earth-time is a vector (every time stamp has a place stamp to go along with it). Since no would think that our place stamps had any significance for other parts of the galaxy, it’s intuitively the case that we need to use magnitudinal time to measure them. Unless we’re relating what time some cosmic event occured with an equivalent time on earth, and in that case we do want to know what point in history it occured at, so we need to translate magnitudinal time into earth-time by taking into account all the leap seconds, leap years, shortened months etc… to give a date that lines up with a historical chronology (Which is all very imprecise anyway).

It seems to me you already have your way – we already have 2 ways of measuring time. Atomic clock atime and earth time. Earth time is the time-of-day (time stamp + place stamp) whereas atomic time is the pure magnitudinal difference you’re asking for.

And of course we ought to subtract or add seconds if a comet messes with our orbit. Why woudn’t they do this? Unless the margin less so much less than a leap second as we didn’t need to.

I think you’re fundamentally misunderstanding what it means for time to be “calibrated” to the earth’s orbit. First of all, this is a special place in the universe, it’s the one we live in. Your notion of a non earth corrected time doesn’t make sense for humans on earth – it’s a derivitive understanding. The originary experience of time is things like seasons, day and night. Midnight at the middle of hte night and midday at the middle of the day. Clock time is a derivitive of that, which we only institutionalized very shortly ago into standard time so railways could have proper schedules. Standard time, however, needs to sometimes be adjusted to get back closer to the medium of pre-standard time – just like pre-standard time sometimes had to add days or weeks to make up for the shift in the seasons. “The Second” use to be calibrated as to a function of a day, but now it has an arbitrary designation. Since it’s different from what it’s used for (measuring days), it needs to be adjusted to keep up with its more original purpose. Time is still being calibrated arbitrarily (and absolutely, or near enough). Earth time, however, needs to match up to the position of the sun in relation to the earth because that’s what time is for.

The notion that non earth corrected time, and that we should just let our clocks run off the relation of earth to sun and stars, I think, is a bit scientistic and rootless. Part of this psychopathic fear of the past (oh my god do you know you’d probably have – oh no – a toothache right now!).

Jenn January 24, 2007 at 7:57 am

“In keeping with the dictates of thesis writing, and the sage comments of those who suggest that blog entries are not the best use of time…”

Any act in which one puts their thoughts into words, whether written in a personal journal or a blog, is a stress reliever and helps the writer formulate cohesive thoughts in regards to the particular subject instead of letting is sit all jumbled up in the noggin. It’s a therapeutic act, so don’t stop or restrain yourself from blogging, it will only add to your anxiety. And I’ll have nothing to read. Haha.

Anonymous January 24, 2007 at 10:01 am

Since our orbit continues to slow, leap seconds need to be inserted with ever greater frequency.

If our orbit is slowing down, that means we’re getting ever closer to the sun.

How long before CO2 becomes the lesser cause of global warming?

Milan January 24, 2007 at 5:04 pm

How long before CO2 becomes the lesser cause of global warming?

Given that we need to deal with a second’s worth of slowing every few years, I don’t think this is an immediate concern.

It’s a therapeutic act, so don’t stop or restrain yourself from blogging, it will only add to your anxiety.

This is true, but it can also be a distraction: especially when I feel the need to investigate something unrelated to any of my academic work.

Milan January 24, 2007 at 5:17 pm

Tristan,

The notion that non earth corrected time, and that we should just let our clocks run off the relation of earth to sun and stars, I think, is a bit scientistic and rootless. Part of this psychopathic fear of the past (oh my god do you know you’d probably have – oh no – a toothache right now!).

It’s not about fear of the past: rather, it’s about a growing recognition of the particularities of our situation. The fact that we’re all now a few seconds older than we really are – to keep the days and seasons of calendar time matching up with our orbital dynamics – seems, to me, rather odd.

As for “psychopathic fear of the past,” you can say all you like to trivialize the bad conditions that people previously lived in, but the fact is that they were pretty abysmal. Lives were short, characterized by illness, excessive infant and maternal mortality, and malnutrition. Progress, both in terms of scientific understanding and the conditions in which people can live, is a real phenomenon.

Milan January 25, 2007 at 1:08 am

On the possibility of blogging being a distraction:

Fact: between June 18th, 2003 and the present day, I have written 742,060 words in blog posts. Those are spread across 1988 different posts, the longest of which was 3523 words.

R.K. January 27, 2007 at 1:29 pm

Robert Louis Stevenson

“Perpetual devotion to what a man calls his business, is only to be sustained by perpetual neglect of many other things.”

Milan June 15, 2007 at 8:14 pm

Perfect silicon sphere to redefine the kilogram

SECURELY tucked away inside a French vault is a lump of metal known as the International Prototype. A mixture of platinum and iridium, it was made in the 1880s to define the mass of a kilogram.

But work by a team of Australians could help pave the way for the retirement of this century- old prototype, as weight and measurement experts across the globe work towards a more scientific definition of the kilogram.

The project requires the development of perfect silicon spheres, and optical engineers at CSIRO’s Australian Centre for Precision Optics — considered world leaders in the craft — are doing their part.

Scientists will use the spheres to determine how many silicon atoms make up a kilogram, and this will be used as the new definition — bringing the kilogram into line with other base units such as the metre and the second, which are all defined by physical constants.

. November 20, 2007 at 9:37 am

Vote To Eliminate Leap Seconds

By kdawson on making-y2k-look-like-a-walk-in-the-park

Mortimer.CA writes “As discussed on Slashdot previously, there is a proposal to remove leap seconds from UTC (nee ‘Greenwich’ time). It will be put to a vote to ITU member states during 2008, and if 70% agree, the leap second will be eliminated by 2013. There is some debate as to whether this change is a good or bad idea. The proposal calls for a ‘leap-hour’ in about 600 years, which nobody seems to believe is a good idea. One philosophical point opponents make is that the ‘official’ time on Earth should match the time of the sun and heavens.”

. June 30, 2008 at 11:19 am

Summer solstice 2008
Friday, June 20th, 2008

Happy Vernal Equinox
Thursday, March 20th, 2008

Precise winter solstice
Saturday, December 22nd, 2007

After the vernal equinox
Monday, March 26th, 2007

Time, and our imperfect orbit
Monday, January 22nd, 2007

Happy Winter Solstice, from Tallinn
Wednesday, December 21st, 2005

. January 18, 2012 at 3:34 pm

Their time has come
Are leap seconds about to be abolished?

Jan 14th 2012 | from the print edition

THE phrase “clockwork universe” is more than a pithy tribute to the exactitude of physics. For thousands of years, the movement of the heavens (or rather, as was eventually realised, the movement of the Earth within the heavens) served as exactly that—a clock. It still does. Even the hyper-accurate atomic clocks now used to record the passage of Coordinated Universal Time (UTC), the globe’s official standard, regularly defer to the addition of so-called leap seconds. These are introduced every so often by the time lords of the International Earth Rotation and Reference Systems Service. Their purpose is to match the relentless stream of regular 86,400-second days that pour out of atomic clocks with the slight irregularities that the Earth experiences in its rotation around its axis.

But possibly no longer. Next week, the International Telecommunication Union (ITU) is meeting in Geneva, and one of the items on its agenda is the abolition of the leap second. If the assembled delegates vote in favour, then the next leap second (which will be added one second before midnight on June 30th, causing clocks set to UTC to display 23:59:59 for two seconds instead of one) will be one of the last—and the answer to the question “what time is it?” will have ceased to have anything to do with the revolutions of the heavens.

Worrying about a few stray seconds may remind some readers of medieval debates about the precise number of angels that could be crammed onto the head of a pin. But, say the abolitionists, time—even small amounts of it—does matter. America’s Global Positioning System satellites, for instance, do not add leap seconds to their internal clocks, and are therefore out of step with UTC. Receivers on the ground can correct for that discrepancy. But the satellite-navigation systems being launched by China, Europe and Russia use still other definitions of time, so exceptions to UTC are proliferating. That has led to worries that mismatched time signals could cause navigation problems, since even small errors in a time signal would mean positions being off by tens of metres.

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