<<I'd heard from different sources that it had been proven, eg:>>
I saw the video link of yours. Reading my reply will take you less than watching the video link.
And again, you are witness of how sensitive atomic clocks are.
They don't work by mechanical means alone but the main method is by the receiving of signals. The atom of Cesium vibrates in a regular frequency. The vibrations of this atom are perceived as signals by a receptor. The receptor has an adapted counting device, and when the receptor counts 9,192,631,770 vibrations, the receptor will make a "tic", this is to say, a second has been counted. And this is a continued counting of the vibration frequency of the atom of Cesium.
As you can notice, there is not any flowing of time (as the flowing of time suggested by the dude in the video you gave as a link) but a simple method very complicated to build, of using the regular motion originated by the vibration of the atom of Cesium, to be compared with the motion of other things.
I had in one of my vehicles, a TV receptor. I installed it myself. I bought it on eBay, one of those devices from China. The receptor worked very well, I was capable to watch digital TV in my car while it was in Parking. But, as soon as I started to move the car, the signals started to suffer of interference.
The method of connecting the wiring had nothing to do with this scenario, because DVD's can be watched with the vehicle in motion. In this case, motion caused interference to the sensitive TV receptor.
The same as well, the atomic clocks were never ever tested against acceleration, the only tests made on atomic clocks were temperature and pressure. So, we have the scenario where the sensitive receptor inside the atomic clock will suffer of interference and/or the atom itself will suffer of change when motion is in progress.
This is a normal and accepted consequence observed in everything exposed to motion. Your body itself feels different when the airplane starts flying, and later the modulated environment created artificially inside the airplane will make you recover some comfort, but remember, that comfort is created by the manipulated environment that the airplane builders have programmed for you.
So, having the atomic clock as a device like any other device called a clock, with the only difference that it goes to a tiniest level of counting to mark what is a second, we can see that the atomic clock is vulnerable to motion and that will malfunction with acceleration or is exposed to any other change of environment.
If time really slows, then you must, this is essential, you must show the current flowing of time without being affected by motion of objects.
This is to say, you must detect such a flowing of time before any changes in it. After you have detected its "regular flowing", then you expose the detector device to fast motion, and the sensor inside the detector device must show you that time indeed slows down.
But, clocks have no sensors, clocks are devices calibrated to make "tic tic tic"
How in the world, this dude from the video, and several nuts from the scientific world, want us to believe that clocks actually detect time and can confirm time dilatation?
The whole idea of time dilatation is absurd, a fantasy, a fake.
There is no way that a clock can detect time, and the real and evidential explanation of the discrepancy of data received by atomic clocks in outer space, or atomic clocks in airplanes or installed in high mountains, is the sensitive receptor suffering in front of environment changes, this is to say, malfunction of the atomic clock.
Any other clock will suffer the same malfunction in different rates, like a sand clock in outer space will -of course- give you a clear demonstration that clocks in general malfunction without exception.