00:02I'm all around you, the universal constant.
00:07No one can contain me, yet I am everyone's most valuable resource.
00:12I am the beating heart of your civilization.
00:24The secondhand ticks beating the very rhythm of our daily lives.
00:28In our hyper-connected society, the role it plays is vital in how we type two, speak with, and even
00:35find each other.
00:38Over the millennia, mankind has sought to master time with increasingly complex machinery.
00:44It's no longer up to watchmakers' workshops to make the best clocks.
00:49Today, we look to our laboratories.
00:53In the Paris Observatory, engineers and researchers observe a timeless tradition.
00:58In their quest for precision.
01:01Mechanical masterpieces have been abandoned for today's high-tech instruments.
01:06And the gentle thrum of the pendulum has given way to steady atomic vibrations.
01:12Here, the masters of time are physicists.
01:15And their tools are clocks of a very special kind.
01:24What you can hear is a sound we call click-clacks.
01:28In a way, it's the measured frequency of the oscillator.
01:32This is the clock that calibrates the official time which we use on the entire French territory.
01:41There is no pendulum, spring, or gearworks within this atomic clock.
01:45All that guarantees the regularity of its rhythm is a tiny bit of metal, for this clock runs off cesium.
01:53It is held within a small glass bulb, which we break inside the vacuum chamber, releasing cesium vapor, that we
02:01then cool with lasers.
02:04Cesium atoms vibrate at an extremely constant rate.
02:07In an atomic clock, an electronic device called an oscillator maintains the seconds.
02:13To ensure that the oscillator keeps perfect time, it is constantly compared to the atomic vibration, which acts as the
02:20system's metronome.
02:22If the frequency of the oscillator falls out of sync, even just a little, a notable energy drop will be
02:28detected at the base of the clock.
02:29We can then force the oscillator back onto the atomic frequency.
02:34The best quartz watches lose about one second every hundred days.
02:39In order to see a cesium clock drift by a second, we would have to wait a hundred million years.
02:48This is why, in 1967, the international community decided to define one second as 9,192,631,770 vibrations of
03:02a cesium atom.
03:03Today, there are more than 400 atomic clocks keeping time around the world.
03:08All of their measurements are centralized here, in Sèvres, a suburb of Paris at the BIPM.
03:15The BIPM, the international organization responsible for units of measurement, then sets Coordinated Universal Time, or UTC, the official standard
03:25time of the modern world.
03:28This desire to synchronize time across international borders has existed for centuries, even back when scientists searched not in atoms,
03:36but in the sky.
03:38Over three centuries ago, astronomers at the Paris Observatory determined the hour using a projection of the sun moving across
03:46a physical line in the ground, the meridian.
03:48When sunlight crossed the meridian, it was noon, local time.
03:53Until a universal standard was adopted, this line was what legally defined time in France.
04:00Over the centuries, measurements became more precise as they were based on the position of the stars rather than the
04:07sun.
04:09In the past, observations were made locally, each observatory calculating time relative to their own meridian.
04:16It didn't take long to realize that a universal system was required, an international meridian to which everyone could adhere.
04:23In 1884, there was an international conference held in Washington, where the meridian in Greenwich was adopted as the international
04:31standard.
04:32This is where Greenwich Mean Time was established.
04:34It's the same standard that we use today.
04:40For centuries, a second was defined as a fraction of a day.
04:44Then, for greater precision, as a fraction of a year.
04:48Finally, on October 13, 1967, a second was defined as a set number of atomic vibrations.
04:56The second had officially shifted from an astronomical measurement to one based on quantum mechanics.
05:04The quest for greater precision is accelerating.
05:08In the basement laboratories of the Paris Observatory, researchers are developing the clocks of the future.
05:15While this clock is more precise than a cesium clock, the technology has to mature before it can serve as
05:22a permanent replacement.
05:24It needs to be able to function 24-7 and link to the clocks developed in other metrology labs.
05:33In the end, cesium could be replaced by strontium, which vibrates 10,000 times faster.
05:39And while it might take 100 million years for a cesium clock to drift by one second,
05:45a strontium clock would keep time accurately for 10 billion years.
05:52These clocks are so powerful, so incredibly precise, that the researchers hope to use them one day
05:58to test the very fundamental laws of physics.
06:04The basic theory of physics is known as the standard model,
06:08which is the theory describing fundamental particles and how they interact.
06:12However, there are astronomical observations that contradict the standard model,
06:17insinuating it may be flawed and should include new particles, dark matter and dark energy.
06:23Thanks to extremely precise clocks, we can observe minute deviations
06:27and try to confirm the theories that go beyond the scope of the standard model.
06:34One of these experiments is set to be carried out on board the International Space Station
06:40with a French atomic clock called FARO.
06:43As it orbits the Earth every 90 minutes,
06:46FARO will have the chance to serve as one of the world's reference clocks as well.
06:51In a way, perhaps this will reassure our astronomers,
06:54who once again will be able to fine-tune their clocks by looking to the skies.
07:24The first thing that I will disenfranchise,
07:25and may somewhat any cause need what stressesings
