What time is it? No not approximately, not about, but exactly. What is the exact time, and not in minutes and seconds, or even in hundredths or thousandths of seconds, but even more accurately? And by the way, who determines the time? Where is this clock, which is the authority to set the exact time for all other clocks in Israel wherever they are: in your phone, computer, or on your wrist; or at the stock market or bank; on a cruise missile or the Iron Dome? And how does all this work, this master clock? How can we trust it? And who gave it the authority to be the one, supreme clock?
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Welcome to the Coordinated Universal Time Laboratory at Hebrew University on Givat Ram in Jerusalem. Meet Dr. Nadya Goldovsky, the person legally in charge of time in Israel. From the door of her modest lab you can see the Knesset, Israel Museum and Bank of Israel; about as symbolic as you can get. Her lab holds a few computer servers, and the only thing that makes a real impression in the small lab is the clock itself: A large red screen, with the seconds ticking off authoritatively, as if it knows it is correct. This is Israel’s national clock.
Officially, Goldovsky is the head of the Laboratory of Frequency and Time of the National Physical Laboratory of Israel, which is under the auspices of the Economy Ministry.
So why does Israel need an official clock, and why is the Economy Ministry responsible for it? Goldovsky explains:
“I am employed by the Economy Ministry, which in the past was the Ministry of Industry, Trade and Employment. Industry needs us, since someone is supposed to hold the standards for all sorts of physical units, according to international standards. For units of length, meter; for units of mass, kilogram; and for units of time, second. My responsibility is the second standard.”
In other words, the ministry decided that if you want to know what exactly a kilogram weighs to test the scale for your greengrocer, or what exactly is the length of a meter to check the table you bought at Ikea, there will be an official authority in charge of these standards.
In 1992 the Knesset passed The Law Determining the Time, which replaced the Time Act from 1940 during the period of the British Mandate. The law states: “The accepted basis for time in the world, for legal purposes, for international coordination and other purposes, is based on the rate of change of atomic time, with adjustment for the movement of the Earth, and is set by the National Physical Laboratory in the Industry and Trade Ministry.”
The lab sets Coordinated Universal Time in Israel. This is abbreviated as UTC, based on the French term. UTC is the international standard, for all clocks around the world – and local time is adjusted by time zones. Once upon a time GMT, Greenwich Mean Time, was the standard, but UTC has replaced it.
Who controls time?
Israel’s official atomic clock looks like a not particularly modern computer case, but inside the box is quite a bit of sophisticated technology. Goldovsky explains how it works:
“In the past we would measure the time according to the rotation of the earth. You would take the day and divide it into 24 hours, then divide the hour into 60 minutes, and the minute into 60 seconds, and that is how you reached a single second. But since then it’s been discovered that the earth’s rotation is not stable and not very precise, but with a deviation of milliseconds. Therefore, we switched to another method: The atom has a nucleus that around it circles the electron, so it is sort of clock in itself. Scientists found a specific atom named cesium [Cs in the Periodic Table] in which the electrons spin around the nucleus at a stable speed and perfect precision. To measure a second you need to look inside the atom with a beam and count the [atomic transitions].” The most accurate clocks have their cesium atoms cooled by lasers down to almost absolute zero, minus 273.15 Celsius.
Every time the electron in the atom completes 9,192,631,770 revolutions, a second has passed. “The accuracy of a cesium clock is 10 to the power of minus 14. An atomic clock is off by one second once in a million years. The atomic clock has been here since 2010 and its working time is between seven to 10 years, and then we will have to replace it,” says Goldovsky.
If you think we have reached the highest extreme of precision, you are wrong: Goldovsky has two clocks, which average each other out all the time – but on the roof of the building are three antennas, which are used to synchronize the local Israeli clocks with dozens of other clocks around the globe in other government standards labs, as well as with dozens of satellites. Many of these atomic clocks don’t actually show the time, but are used to broadcast precise frequency signals, which are then used by other clocks.
“We conduct comparisons all the time with atomic clocks in 60 countries,” she says. “In addition, we conduct comparisons with atomic clocks on the American GPS system of satellites, the European satellite system Egnos [European Geostationary Navigation Overlay Service], and the Russian satellite system Glonass. Every second we collect data from all of these,” she said.
The control of time is to a great extent also a matter of global politics. The Russian Glonass system, which competes with the American GPS system, was rather neglected until Russian President Vladimir Putin decided to revive it. The Europeans, who do not want to remain dependent on either the Russians or the United States, are building their own system named Galileo. The institution at the center of all this time coordination sits in Paris, and is named BIPM. By going to their bipm.org website you can see the almost perfect UTC time, since it also adjusts itself for the time delay you see over the Internet. But BIPM is still dependent on the Americans, who control the movement of the satellites, from Colorado.
Clock for Iron Dome
You can find atomic clocks outside labs too. “There are 10 such clocks in Israel,” said Ehud Sharar, owner and CEO of Focus Telecom, which sells and implements atomic clock systems in Israel. “Atomic clocks are behind the scenes in almost every system we use. In communications systems there are atomic clocks since they need to be synchronized, and sometimes inaccurate clocks lead to dropped calls. Banks and other financial institutions also use such clocks since every financial transaction comes with a time stamp, as does all stock market trading. The government’s websites are also synchronized with Focus Telecom’s clocks, as well as the Bank of Israel, Israel Electric Corporation control rooms, Tel Aviv Stock Exchange and the IDF’s communications networks.
Take for example a military system such as Iron Dome: It has a radar system that identifies the attacking missile, it transfers the information to a computer that estimates where the missile will fall, and then it needs to give an order to the launcher so the missile will hit the attacker. All this must be synchronized and the atomic clock is the conductor of the orchestra. There are atomic clocks in cruise missiles, in shells and i other weapons systems,” said Sharar.
The use of atomic clocks is growing too, he says. One of the major uses in recent years is in the area of geology and offshore gas and oil exploration. Geologists use acoustic waves to search below the sea bottom and, based on the time it takes for these waves to return, they can calculate the density of the earth – and whether there is gas or oil and at what depths. To analyze the data requires extremely exacting time readings, and they use atomic clocks, says Sharar.
As for the cost of such a clock, he says it varies. The one in the national laboratory costs about $70,000. The smallest one ever developed was made for the U.S. military, and can fit in a soldiers’ equipment pouch, and is used in helping neutralize explosive devices. Such models can cost only $1,500 to $3,000, says Sharar. There are cheaper models, costing only a few hundred dollars apiece, but instead of cesium they use rubidium atoms, and are a bit less accurate. Accubeat, a subsidiary of Rafael Advanced Defense Systems, sells such clocks. And if you really want one, you can buy a wristwatch atomic clock from Bathys Hawaii for only $12,000.
The daily routine in the Israeli national time lab includes a long list of tests for all the clocks, the satellite receivers and continual checks with the BIPM in Paris, as well as repairs and calibrations. Much of the time is used for providing services: Many well known technology companies and defense contractors make pilgrimages to the lab and give Goldovsky their atomic clocks for calibration, which can take up to 10 days in some cases.
Once every few years there is a dramatic moment in the time-keeping world, or rather a dramatic second. It is necessary to change the clocks and add a leap second, explains Goldovsky. Because the earth day is not exactly 24 hours and the rotation speed of the earth changes, it is sometimes necessary to add a second to adjust UTC to the actual physical time of the rotation of the earth. In such a case it is announced six months in advance. Twenty-five leap seconds have been added since 1972, the last one coming on June 30, 2012. Otherwise the small difference would add up and “in a couple of hundred years we would be eating lunch in the middle of the night,” said one of the experts.
Just before we leave the time lab, I stop for a second in front of the big clock and adjust my watch. After all, there are very few such opportunities in life.