Time dilation is not an illusion but a well-established phenomenon supported by experimental evidence and consistent with the principles of special relativity. It is not the matter itself that slows down during high speeds, but rather the passage of time as observed by different observers in relative motion.
In the context of high-speed motion, such as in the famous atomic clocks experiment, the behavior of clocks and atomic processes is indeed affected by time dilation. Time dilation arises from the fundamental properties of spacetime and the constancy of the speed of light.
The experiment you mentioned involves comparing two highly precise atomic clocks—one on Earth and the other on a high-speed jet or satellite. When the high-speed clock is brought back and compared to the clock that remained on Earth, a time difference is observed.
From the perspective of the clock on the high-speed object, it experiences less time passing compared to the clock on Earth. This is because, relative to the clock on Earth, the high-speed clock is moving at a high velocity. The effects of time dilation, caused by the relative motion between the clocks, result in a measurable time difference.
It's important to note that the behavior of atomic processes and clocks, including the oscillations and transitions of atoms, are influenced by the fundamental principles of special relativity. The relativistic effects of time dilation affect the measurement of time intervals and the ticking rate of clocks.
In summary, time dilation is not an illusion but a real physical phenomenon. It is not the atoms themselves that slow down, but rather the passage of time as experienced by observers in relative motion. The behavior of clocks and atomic processes, including the atomic clocks used in experiments, are influenced by the effects of time dilation.