00:03Sous-titrage Société Radio-Canada
00:30We say that our mirrors are the most perfect mirrors, in part because the glass we use is the purest,
00:35which leaves an absolute minimum of interior defects.
00:39And on the other hand, these mirrors reflect the quasi-totality of incoming light, thanks to a unique combination of
00:46manufacturing techniques that this lab has perfected.
00:53The coating on the surface is 0.007 millimeters thick, or 7 microns.
01:00And the reflectivity goes from 4% to 99.9999%.
01:06The coating process takes around 40 hours.
01:15This ultra-reflective property is hard to show on camera, especially when talking about infrared light, which is invisible to
01:22humans.
01:25But infrared light and the ultra-reflective mirrors are key elements in massive gravitational wave detectors, like LIGO in the
01:34United States, or Virgo in Italy.
01:39These disproportionately large machines, with arms that stretch for 3 to 4 kilometers, measure the trembling of our universe.
01:47Waves within space-time itself, produced by cataclysmic events, like the collision of two black holes.
01:55But the signals that make it to Earth are incredibly weak.
01:58To measure these disturbances in space-time, detectors LIGO and Virgo use a technique called interferometry.
02:05A laser is divided by a special mirror.
02:08The beams then travel along the two arms before being reflected back and recombined, where, as they are in opposing
02:15phases, they cancel each other out.
02:18If the lengths of the arms change as a gravitational wave passes through, an anomaly is produced in the interference
02:25of the laser.
02:25This renders the wave detectable.
02:28For it to work, the laser must be extremely stable, and the mirrors as perfect as possible.
02:35The scientists are therefore reliant on the most advanced technologies in the world.
02:40The mass of the mirror, a block of exceptionally pure glass, sees daylight for the first time after months spent
02:46under production in Germany.
02:48The glass then leaves for California, where it undergoes the finest polishing.
02:54Once polished, it again crosses the Atlantic and makes its final manufacturing stop in Lyon, here, in the Advanced Materials
03:01Lab, for a surface treatment that will make the mirror reflective.
03:10This surface treatment must be done within the largest machine of its kind, which was also developed here in the
03:16lab.
03:20So this machine is an ion beam pulverizer, which we use to make these extremely high-performing optics.
03:26All of the gravitational wave detectors in the world, whether they're used in the United States, Japan, or the one
03:31in Italy,
03:32all of their principal or critical mirrors are created in the heart of this machine.
03:37In total, each mirror requires two years of work before it can be integrated into a gravitational wave detector.
03:44And the conditions in which every step is completed must be heavily controlled, like temperature, hygrometry, and cleanliness.
03:52But how can we know the process worked, that there were no errors?
03:56For something as finely tuned as these optics, each alteration, every change to the mirror must be rigorously controlled before
04:04passing on to the next step.
04:08So this system enables us to measure how flat the finished product is.
04:13Our goal is to create deposits with depths of only a few angstroms.
04:16In other words, just a few atoms thick, which is very, very thin.
04:24So the scale skews things a little, accentuating the effect.
04:28What we see on the screen, between the blue in the middle and the red on the periphery, is a
04:33difference of only two nanometers.
04:35And one nanometer is about ten atoms thick.
04:40So, as you can see, we're awfully close to perfection.
04:47Flirting with perfection, these efforts were rewarded in 2016 after the first and long-awaited detection of gravitational waves initially
04:55predicted by Einstein a hundred years ago.
04:59After 20 years of work, we saw the final result of the immense effort we put in.
05:04For the younger members of our team, closer to ten years.
05:08So there's a real sense of personal pride for everyone on this adventure.
05:12And that motivates us to continue pushing forward.
05:15Because now we know that these waves exist.
05:18The discovery was a beautiful thing to witness.
05:20And there are plenty more beautiful things to work on here in this lab.
05:25Once the work is finished here, the precious mirror is delicately packed up.
05:31Chances are, it will be sent to one of the great detectors observing the universe.
05:35Where it will participate in new gravitational adventures.
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05:42Where it will be sent to one of the dangers of investigatrices.
05:46The immersive pathways cars are readily packed up.
05:51And there are only two dark pictures.
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06:00The reality opens on Speed of managing our approach…
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