The phenomenon of 'time reversal', which has long been predicted to exist only in theory within the scientific community, has been observed for the first time through experiments conducted in New York. Researchers demonstrated that, thanks to a specially designed metamaterial, electromagnetic waves can move backward in time and undergo frequency changes.
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For the first time, scientists have experimentally demonstrated that electromagnetic waves can reflect not only in space but also in time.
In a study published in Nature Physics, the observation of time reflection was made possible in a laboratory setting using a specially designed metamaterial. This phenomenon, previously known in theory, could not be tested in practice due to the challenging energy requirements and conditions.
In this experiment, the medium through which the electromagnetic wave travels is altered abruptly and synchronously, causing a portion of the wave to reverse its course in time and change its frequency.
The research involved sending broadband signals across metal strips equipped with electronic switches and capacitors. By triggering the switches synchronously, the impedance of the medium was altered, resulting in a time-reversed copy of the signal. Gengyu Xu, one of the authors of the study, stated, 'Electromagnetic waves move at a rapid pace; altering the properties of a medium synchronously and swiftly is challenging. We managed to accomplish this with the switches added to the metamaterial.'
According to researchers, if you were able to gaze into a 'time mirror', you would see not your face, but your back. The reason for this is that the last part of the signal returns first. To explain this effect with an acoustic analogy, it's like rewinding and listening to a sound recording; the sound becomes higher-pitched and speeds up. In the case of light, there are frequency shifts; a red light could suddenly turn green.
Andrea Alù, Director of the Photonics Initiative at the CUNY Advanced Science Research Center, commented, 'The experimental observation of this phenomenon has brought a half-century-old theory into reality. Time reflections behave completely differently from spatial reflections.'
Scientists emphasize that time reflections are not merely a theoretical achievement. This kind of precise control could enhance wireless communication technologies and pave the way for a new generation of wave-based, energy-efficient computers.