00:00This little amulet, the sole survivor of a distant past, is at the heart of a scientific mystery.
00:09It was discovered in 1985 on an archeological dig at Mergarh in present-day Pakistan, its age over 6,000
00:20years old.
00:23Scientists have long been unable to discern the process that created this amulet, now heavily
00:29deteriorated with the passing of time.
00:31The stakes are high, as this amulet has immeasurable historical value.
00:38This amulet is extraordinary because it's the first known clue of wax casting, an important
00:45metallurgical technique.
00:47The idea is to mold the wax into a model we can use, so we'll take the wax, which has
00:53similar properties to sculpting clay, and with it, make a wheel.
01:01The model is then coated in clay, which will become the mold.
01:05We'll heat the mold to melt and drain the wax through a small hole.
01:12Once the mold is empty, we'll bake it, and then pour metal inside.
01:17Then, to get the metal wheel out, all we need to do is break the mold.
01:23This technique isn't so much the mystery.
01:26That stems from the type of metal used by its makers.
01:30Chemical analysis indicates that the object only has copper compounds, as if artisans of
01:36the day only used pure copper.
01:39However, under the microscope, we can see branching structures that formed, called dendrites, with
01:45the kinds of crystals one would expect to find in alloys.
01:49This contradiction has pushed researchers to test new analytical techniques.
01:55In order to better probe this small metal ring, another, larger ring has entered the fray.
02:01The Soleil synchrotron in the southwest of Paris has made it possible to study the photoluminescence
02:08of the amulet.
02:09The technique involves bombarding the ring with light rays and analyzing the light re-emitted
02:15by its different compounds.
02:18The rays we pick up from the synchrotron will primarily be ultraviolet, or even far ultraviolet,
02:24which we'll detect through this microscope.
02:26We'll focus the beam on the sample, which will become excited.
02:30We will then be able to collect the photoluminescence along the same optical path and record it on
02:35the camera here.
02:38This method reveals details otherwise invisible to other imaging techniques.
02:44Minuscule rods become readily apparent and are instantly recognizable by specialists as
02:50copper oxides.
02:51And here lies the key to the mystery.
02:53The strange element, alloyed with the copper, was oxygen.
02:58Ancient artisans chose very pure copper, and, during the fusion of the metal, oxygen was
03:04incorporated by accident.
03:06This was what created the internal branching structures.
03:09The rest of the amulet was then oxidized over millennia.
03:13Only photoluminescence could differentiate between the two types of oxidation.
03:19I think that materials like this have only just begun pushing us to develop new techniques.
03:25The opportunities here are enormous for us to learn more about ancient societies, and,
03:30in this case, to create standards for putting these new methods to use.
03:34With new technologies like these, scientists can revisit other ancient relics whose traditions
03:41and methods of creation have long been lost, and continue to pierce the mysteries surrounding
03:47these vestiges of the past.
04:06WHATE sociedad always pill head the eruICE of science of fire.
04:09The language像 showed us perfectly through zehn weeksия from the next three times according
04:09C'est parti !
