Time reflections are real

Scientists have recently confirmed the existence of time reflections.

For over 50 years, scientists theorised that an electromagnetic wave could be reflected temporally - not just spatially. Using engineered metamaterial scientists in New York City have successfully observed time reflections for the first time.

The explanation of spatial reflections, by light or by sound, are intuitive, they consist of electromagnetic radiation in the form of light or sound waves that could hit a ‘mirror or wall’, respectively, and change course. This allows our eyes/ears to see/hear a reflection or echo of the original input.

This has been really exciting to see, because of how long ago this counterintuitive phenomenon was predicted, and how different time-reflected waves behave compared to space-reflected ones.

But scientists also theorised another kind of reflection in quantum mechanics known as time reflection. Time reflections occur when the entire medium in which an electromagnetic wave travels suddenly changes course. This causes a portion of that wave to reverse and its frequency transforms into another one.

Because these time reflections require a uniform variation across an entire electromagnetic field, scientists assumed it would require too much energy to observe time reflections in action.

But scientists from the Advanced Science Research Center, City University New York, (CUNY ASRC), successfully observed time reflections by sending broadband signals into a strip of metal filled with electronic switches that were connected to reservoir capacitors. This allowed the researchers to trigger the switches at will, doubling impedance along the strip. This sudden change caused the signals to carry a successful time-reversed copy. The results were published in the journal Nature Physics.

“It is very difficult to change the properties of a medium quick enough, uniformly, and with enough contrast to time reflect electromagnetic signals because they oscillate very fast,” Gengyu Xu, a co-author and post-doc student at CUNY ASRC. “Our idea was to avoid changing the properties of the host material, and instead create a metamaterial in which additional elements can be abruptly added or subtracted through fast switches.”

This time reflection also behaves differently than spatial reflections. Because this time echo reflects the last part of the signal first, the researchers say that if you looked in a time mirror, you would see your back instead of your face. To translate the experience acoustically, it would be like listening to a tape on rewind, probably fast and high-pitched.

The shift in frequency, if perceived by our eyes/ears, would seem like colours of light suddenly changing to another colour, such as red to green. This strange counter-intuitive nature of time reflection is part of what has made studying the concept so difficult so far.

Corresponding author Andrea Alù, physics professor and director of CUNY ASRC’s Photonics Initiative, said, “This has been really exciting to see, because of how long ago this counterintuitive phenomenon was predicted, and how different time-reflected waves behave compared to space-reflected ones”.

A big question: Why have scientists worked creating theoretical time reflections in a laboratory? Well, more minute control of electromagnetic waves can significantly improve wireless communications and even lead to advancements in low energy, wave-based computers - a significant step forward in understanding how time lays down its temporal tracks.

Read more at:  bit.ly/3JVgDKh