Blog Archive for the ‘Clock of the Long Now’ Category

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Emerald Observatory iPad app

Posted on Friday, December 3rd, 02010 by Paul Saffo
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This is my hands-down favorite clock for the iPad, and could well be the coolest astronomic/civil clock I’ve ever seen:

Emerald Observatory has everything a time geek could ever want, plus everything an astro geek would want, all in a stunningly elegant interface.

[decription below from Emerald]
Emerald Observatory displays a wealth of astronomical information all on one screen, in a unique but understandable format.

  • Times of rise and set for the Sun, the Moon, and the 5 classical planets
  • Times of the beginning and ending of twilight
  • Heliocentric orrery (display of the planets in orbit around the Sun)
  • Altitude and azimuth for the same bodies (one body at a time)
  • Current phase and apparent orientation and relative size of the moon
  • Current regions of day and night on a world map
  • The Equation of Time, solar time, UTC time, and sidereal time
  • Month, day, year, and leap-year indicator
  • Daily alarm
  • Displayed times are synchronized via NTP to “atomic clock” standard
  • Uses iPad location, or the latitude and longitude may be set manually

A setting is available to allow the display to stay on continuously.

Tap on the display to move forward by a month, day, year, or minute.

If you are having any trouble with the application whatsoever, please see our FAQ on the support page listed below and then contact us through that page if your problem is not resolved. We take pride in responding promptly to all support email requests.

10,000 Years of stellar motion

Posted on Tuesday, November 2nd, 02010 by Alexander Rose - Twitter: @zander
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10,000 Years of star motion Credit: NASA, ESA, and G. Bacon (STScI)

There is an interesting bit of astronomy published over at sent to me by way of Danny Hillis and Tom Shannon.  Apparently astronomers focused Hubble on a certain region of Globular Cluster Omega Cantauri several times over 4 years.  They were then able to calculate how each of those stars will move in the next 10,000 years.  You can see a video of this after the jump on their site here.  It reminds me of our recent blog piece on how the constellations will change over the next 50,000 years.  All of this is of interest to us on the Clock project as one of the main references we use is an image of the night sky for one of our slowest moving dials.  We have to choose stars that do not move very much over the next 10,000 years to use as a good reference in the 26,000 year precessional cycle.

Prague Astronomical Clock – 600th Anniversary Show

Posted on Wednesday, October 13th, 02010 by Alexander Rose - Twitter: @zander
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The 600 Years from the macula on Vimeo.

Member Trey Darley sent in this absolutely stunning video mapping show done for the 600th anniversary of one of the greatest clocks ON the planet:  The Astronomical Clock in Prague.  This was done a few days ago on October 9th. Worth watching all the way through.

Prague has a 600 year head start on The Clock of the Long Now, maybe they will be the first to reach 10,000…

BB reader Kerray says, “The people who worked on it are, and, and the projection itself was done by Four months of work, 5000×1200 resolution, 2x Christie 18K HD projectors.” .

From Wikipedia, this schematic explaining what the various interlocking dials on the Prague Orloj represent.

(A lot of people documented it if you want to see other vantage points)

Sound Tower Event with Misha Glouberman

Posted on Friday, September 10th, 02010 by Danielle Engelman
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Long Now has been invited by experimental artist Misha Glouberman to be a partner in a commissioned performance he’s created for Ann Hamilton’s Sound Tower – an 80-foot tall site-specific sculpture located on the Oliver Ranch in Geyserville.   This participatory event takes place on Saturday September 25, 02010 in Geyserville California.

Terrible Noises For Beautiful People is a performance where all the sounds are made by the audience, using their voices, in a series of structured improvisations and games led by Misha Glouberman. Glouberman predicts “some amount of yelling, a certain amount of running around, and also some really quiet parts,” and hopes to create an audible environment that will be exciting, alarming, and sometimes beautiful.

The Sound Tower has a resonance for Long Now as both Ann Hamilton and the Clock Team used the Well of St. Patrick in Orvieto, Italy as a source of inspiration.   Ann Hamilton, for this site specific, 8 story high Sound Tower and Long Now, for the underground chamber that the Chime Generator and other Clock components will be placed in for the 10,000 Year Clock.  This is a chance to feel what it may be like to visit part of the Clock.

Limited tickets for the Saturday performance are available for Long Now Members and their guests, there are 2 additional nights of this performance which are open to the public through a partnership with the Arts Council of Sonoma. Please email events (at) longnow (dot) org for more information.

Pendulum, Escapement Prototypes Installed in Museum

Posted on Thursday, June 24th, 02010 by Austin Brown
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photos by Contessa Trujillo

After its initial public appearance at this year’s Maker Faire followed by an evening at the Exploratorium, the escapement, circular pendulum and Clock face were installed at our Long Now Museum and Store at Fort Mason Center and can be viewed seven days a week – just check our website first for our hours.

About the escapement, circular pendulum and Clock face:

 Escapement Maechanism for the 10,000 Year ClockThis pendulum and escapement represent a snapshot of our development process in timekeeping for the monument size clock. The dials in the center are non-functioning in this model and were used as a visual mock-up for a scaled up version. The function of the escapement is to both drive the pendulum and transfer the regular beat of the pendulum to the timekeeping elements of the Clock. This allows the Clock’s stored energy to ‘escape’ at a regular rate, thus advancing the drivetrain and displays in a manner that allows them to keep time.

This particular pendulum and escapement system is unique in several ways, one of which is likely obvious at a glance. The large ring around the face is actually a pendulum suspended on a specially designed flexure. With most pendulums, the weight is completely below the point of rotation and the distance between the two is what determines the period (the time between ticks). The ring configuration in this pendulum adds weight above the point of rotation, which causes it to swing more slowly than it would otherwise; the period is 10 seconds. By reducing the number of ticks the Clock will go through, the rate of wear can also be reduced.

The second unique element of this mechanism is in the small gear system above the pendulum; the escapement itself. Danny Hillis explains:

One problem with clock escapements is that there is normally some variability in the drive torque of the escape wheel, which can lead to variability in the energy applied to the pendulum. This can in turn lead to inaccuracies in the clock’s ability to keep steady time. One method of reducing this variability is delivering the impulse to the pendulum indirectly through an intermediate energy storage device that delivers a more constant impulse. For example, in a typical gravity escapement, the torque from the escape wheel is used to lift a weight to a fixed height, and the dropping of that weight delivers the impulse. This isolates the strength of the impulse from the torque applied to the escapement, but it does not solve the problem entirely, because the energy that must be removed from the pendulum to release the escape wheel may still depend on the torque applied to the escapement.

The two-phase detached escapement solves this problem by releasing the escapement wheel utilizing the residual energy of the falling gravity arm’s weight. This happens after the gravity arm has delivered its impulse to the pendulum. Because the interaction with the escape wheel only happens after the escapement has delivered its impulse, the escape wheel cannot affect intensity of the impulse. In the first phase, the pendulum releases the gravity arm, which is decoupled from the escapement and the falling gravity arm impulses the pendulum. In the second phase the gravity arm continues to fall until it becomes totally detached from the pendulum, and then the falling gravity arm releases the escape wheel, which restores the gravity arm to the initial position and the escape wheel continues rotating until it is no longer in contact with the gravity arm.

Clock Face for 10,000 Year ClockAt the center of the pendulum is a prototype for the Clock’s face. Rather than hours and minutes, the face displays information about the movement of the sun, stars and moon. The outer ring is shows the movement of the sun; it rotates once per day, passing horizon indicators that show sunset and sunrise. Those horizon indicators change along with the seasons to show the progressive lengthening and shortening of days. The next ring into the center reveals the current phase of the moon and it will rotate along with the lunar cycle; all 32 phases of the moon are shown by this ring.

The center of the face shows the stars of the night sky. The face is intersected by six arcs collectively known as the rete. The wide arcs represent the horizon, so that above them the stars that can be seen at a given time are visible. Stars below those arcs will not be currently visible as they’re blocked by the planet you’re standing on. The four arcs that terminate near the center point towards the celestial north pole, the point around which we observe the stars rotating. Polaris is currently the closest star to that point, which is why we call it the North Star, but as the earth’s axis precesses, Vega will move closer to that position and become our “North Star” in about 13,000 years. On the Clock’s face, the rete rotates along with the earth to show the daily movement of the stars. To account for the axial precession, the black surface with the stars on it will turn around in a 26,000 year-long rotation.

The woman that programmed the first computer

Posted on Thursday, June 17th, 02010 by Alexander Rose - Twitter: @zander
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“Long Shorts” – short films that exemplify long-term thinking.  Please submit yours in the comments section…

Information Pioneers: Ada Lovelace from Information Pioneers on Vimeo.

This is a nice intro to Ada Lovelace, the first computer programmer who wrote programs for Babbage’s mechanical computer. While this computer is similar to the binary mechanical computer used in the first 10,000 Year Clock prototype, Babbage’s computers are decimal based.

Climate Change and Accurate Timekeeping

Posted on Monday, May 24th, 02010 by Alexander Rose - Twitter: @zander
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One of the critical elements of the Clock of the Long Now to keep good time over ten millennia is the part of the clock that is synchronized to solar noon. We have several schemes that allow this mechanical synch from sunlight, but one of the questions that came up as we designed these systems, was how much we might expect solar noon to drift in 10,000 years.  We had already compensated for the earth’s ~26,000 year precessional cycle, and the average rotational dampening of about a second per century, but it was not until Danny Hillis requested this paper from Astrophysicist Michael Busch that we appreciated how much climate change will play a role.

Many people bring up the recent earthquake and tsunami events that have altered the earth’s rotation, or even the filling of the Three Gorges Dam.  While those events have a theoretical effect, it is so minute that they are generally not detectable empirically.  Polar ice however is the real game changer, it could effect when solar noon is over 10,000 years by weeks not minutes or seconds.  Below is the paper by Busch for your reading pleasure…

Climate Change and the Clock
Michael W. Busch
2010 April 9

Based on a request from Danny Hillis for a check of the Clock’s accuracy requirements

There is now a consensus that the Earth’s climate is changing and that it can be greatly influenced by human activity. While we can argue about predictions of the particular form climate change will take, any changes in the climate will have important effects on the Clock.

The most direct effect will be power: the Clock’s core oscillator is powered by focused sunlight. Climate changes leading to frequent clouds over the site in the American Southwest would interrupt that supply. This is not likely to be fatal, since the Clock can operate for fifteen years without sunlight and even the cloudiest places on Earth have sunny days more often than that. But climate change will also affect the Clock indirectly, by disrupting its timekeeping.

The Clock keeps the oscillator calibrated by resetting it at local solar noon – the time of day when the sun is directly south as seen from the mountaintop – at the solstice. On cloudy days, the oscillator keeps running without being reset, and begins to drift away from the true time. However, again, unless the weather becomes implausibly bad at some point in the next ten millennia, the errors in the oscillator will not grow to an entire day before it is reset, and the overall count of how many days have passed will be correct. The problem is connecting the number of days the Clock has counted to the true amount of time that has passed. For everyday life, we treat days as being all the same length (86400 seconds from one solar noon to the next), but they are not. In addition to slight changes in the time of noon on each rotation of the planet since the Earth’s orbit is not quite circular, the length of the day is determined by how fast the Earth spins, and that changes slightly all the time (Hide & Dickey 1991). From day to day, some amount of angular momentum is transferred between the solid body of the Earth and the atmosphere. Adding angular momentum to the Earth makes it spin faster and makes the days shorter, and taking angular momentum away makes the days longer. Each year, a large amount of water moves from the equator to the high latitudes as snow and back again as water and water vapor. Moving mass from the equator to the poles means that the same mass can spin faster with the same angular momentum, and the days get shorter. The standard analogy here is a figure skater pulling his arms in to spin faster.

For the Clock, these daily and yearly changes in the length-of-day average out and do not matter too much. But there are longer term and much larger changes in length-of-day. Mountain ranges get raised up and oceanic crust gets subducted, moving mass around. Earthquakes and the emptying and filling of lakes move around much smaller masses, which can also be estimated. The tides from the Moon and the Sun are slowly subtracting angular momentum and spinning the Earth down. These trends can be measured and estimated over millennia by comparing records of solar eclipses. Over the last 3500 years, the length of the day has increased by 84 milliseconds, give or take a few (Stephenson & Morrison 1995).

Having the length of day off by about tenth of a second may not seem like much, but over ten thousand years it adds up to a difference of several hundred thousand seconds (a few current days) between an estimate of the time based on how many days there have been and the true amount of time that has passed. The tide-produced natural change in the length-of-day can be predicted and corrected for in the design of the Clock. The Earth has been spinning down at a roughly constant rate for more than three thousand years. But climate change may change that.

One of the most dramatic climate change predictions is the possibility of large changes in the mass of the ice sheets in Greenland and Antarctica. Doubling the mass of the ice sheets or completely melting them takes many hundreds of years, if the most extreme instances during the last ice age are a guide (Clark & Mix 2000), but that is far less than the lifespan of the Clock. Just as seasonal motions of water change the length-of-day, so does either melting the ice sheets into the ocean or freezing more ice into them (Trupin 1993, Wahr et al. 1993, Nakada & Okuno 2003). The ice sheets are near the poles. Melting the current ice sheets completely would move about 0.001% of the Earth’s mass from near the pole to much nearer to the equator (since the ice goes into the oceans), and increase the length of the day by roughly 1 second. Freezing out ice sheets comparable to the last glacial maximum would put four times that much mass near the poles, making the day about 4 seconds shorter.

The current Clock design calibrates the oscillator at the solstice. The time of the solstice is determined by the direction of the Earth’s rotation axis relative to its orbit around the Sun, and not by the length of the day. If the conversion from the day count to true time is off by more than about 20 days, the Clock won’t be able to connect the oscillator to the Sun, and the accuracy will rapidly decay. This is only of concern if there is a large change in the length-of-day that lasts for most of the Clock’s lifespan.

Since climate change is a chaotic process, and human decisions and actions in the next several centuries are very likely to have a significant effect on it, it is impossible to predict the length of the day to better than a second or so over the next ten thousand years. The inherent uncertainty in the future climate places a limit on the accuracy of the Clock. It can measure time to about ten parts per million, or a few weeks over ten thousand years.


  • Clark, P.U., Mix, A.C., 2001, Ice sheets and sea level of the Last Glacial Maximum, Quat. Sci. Rev. 21, 1-7.
  • Hide, R., Dickey, J.O., 1991, Earth’s variable rotation, Science 253, 629-637.
  • Nakada & Okuno, 2003, Perturbations of the Earth’s rotation and their implications for the present-day mass balance of both polar ice caps, Geophysical Journal International 152, 124-138.
  • Stephenson, F.R., Morrison, L.V., 1995, Long-term fluctuations in the Earth’s rotation: 700 BC to AD 1990, Phil. Trans. Phys. Sci. & Eng. 351, 165-202.
  • Trupin, A.S., 1993, Effects of polar ice on the Earth’s rotation and gravitational potential. Geophys. J. Int. 113, 273-283.
  • Wahr, J., Dazhong, H., Trupin, A., Lindqvist, V., 1993, Secular changes in rotation and gravity: Evidence of post-glacial rebound or of changes in polar ice? Adv. Space Res. 13, 257- 269.

Scientists vs. Pulsars

Posted on Wednesday, April 14th, 02010 by Austin Brown
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Technology Review has an article up in which some physicists defend their clock-making chops.  It seems they feel pulsars are getting more credit than they deserve in the public perception of accurate time-keeping:

So accurate are pulsar signals that when they were discovered, astronomers gave serious credence to the idea that they were evidence of intelligent life elsewhere in the Universe because they were unmatched by anything physicists could make on Earth. This has lead to the widespread belief that pulsars are the most accurate clocks in the Universe.

John Hartnett and Andre Luiten at the University of Western Australia want you know that’s no longer the case.

Today, the best optical lattice neutral atom clocks and trapped ion clocks have a frequency stability approaching one part in 10^17.By contrast, as more pulsars have been discovered, their timing stability has improved by less than an order of magnitude in the last 20 years. The best millisecond pulsars have a stability of only one part in 10^15 at best.

That means that terrestrial clocks can rightly be crowned the best clocks in the Universe, say Hartnett and Luiten.

Duly noted.  It seems worth pointing out that the measure of accuracy in the article is expressed as a ratio without units – often you hear that an atomic clock will lose a second of accuracy only every 10 billion years or so.  The author of this article avoids that, and maybe for good reason.  Sometimes people told Long Now is building a 10,000 Year Clock react by asking, “Oh, like an atomic clock?”   It seems that an occasional side-effect of using these long time units to illustrate the accuracy of atomic clocks is the implication that they will be around for eons.

The thing is, atomic clocks rely on vacuum-sealed chambers full of cesium atoms kept near absolute zero or similarly complicated mechanisms to make their extremely precise measurements.  That kind of hardware requires a significant technological, economic and bureaucratic infrastructure to maintain.  If you can imagine finding an atomic clock after the electricity failed that kept it running, you would have to recreate a lot of knowledge to understand what in fact it was.

The article goes on to discuss the difficulty of building a timepiece durable enough that its lifespan requires scientific notation to describe, and mentions Long Now’s attempt through the Clock of the Long Now. It’s in this endurance category, however, that pulsars maintain their dominance, as they’re likely to last quite a bit longer than anything humans have been able to build, even Long Now – we’ve been able to observe some that are thought to be around 200 million years old.

(Where Is the Best Clock in the Universe? – Technology Review)

Prototype I, Book of Drawings

Posted on Monday, April 12th, 02010 by Austin Brown
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Long Now has compiled a record of all of the drawings made to create the first 10,000 Year Clock Prototype into a new book. Geared towards the mechanically inclined, this book has the technical drawing of every part used in the first prototype. It also includes several math notebooks and spreadsheets that Danny Hillis used to make the underlying calculations for parts of the Clock.

Long Now hopes that the widespread distribution of these plans will ensure that the knowledge and work that went into building our first Clock prototype is not lost and that this will help the survival of the Clock itself and the long-term thinking it represents.

The paperback book is available through Amazon (we do get a % of sales) and is $19.95. The drawings are also available to download for free on our site.

Resetting the Zero Point of Civilization

Posted on Friday, March 5th, 02010 by Alexander Rose - Twitter: @zander
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A pillar at the Gobekli Tepe temple near Sanliurfa, Turkey.  (photo:  Berthold Steinhilber/Laif-Redux)

A pillar at the Gobekli Tepe temple near Sanliurfa, Turkey. (photo: Berthold Steinhilber/Laif-Redux)

The good folks at Atlas Obscura pointed me to this fantastic story on an archaeological find near the Syrian Border in Turkey that pushes back the date of great stonework, and in effect the beginning of known civilization, by many millennia. (snippet below)

Standing on the hill at dawn, overseeing a team of 40 Kurdish diggers, the German-born archeologist waves a hand over his discovery here, a revolution in the story of human origins. Schmidt has uncovered a vast and beautiful temple complex, a structure so ancient that it may be the very first thing human beings ever built. The site isn’t just old, it redefines old: the temple was built 11,500 years ago—a staggering 7,000 years before the Great Pyramid, and more than 6,000 years before Stonehenge first took shape. The ruins are so early that they predate villages, pottery, domesticated animals, and even agriculture—the first embers of civilization. In fact, Schmidt thinks the temple itself, built after the end of the last Ice Age by hunter-gatherers, became that ember—the spark that launched mankind toward farming, urban life, and all that followed.