Science & Technology

Scientists prove the existence of 'time reflections' for the first time

By T.K. Randall
December 27, 2025

Image: AI-generated (Midjourney) Standard mirrors are easy to explain and observe; shine light on a mirror, for example, and you will see it reflected back at you - but there is another form of reflection that is so exotic and strange that, until now, nobody has been able to confirm that it even exists at all.

Known as a time reflection, this peculiar phenomena occurs when the medium in which electromagnetic waves are traveling suddenly changes direction, causing a portion of the waves to reverse.

It's difficult to explain what this means in practice, but imagine if you looked at yourself in a mirror and instead of seeing your face you saw the back of your head...

Up until recently, scientists believed that it simply wasn't possible to actually reproduce time reflections experimentally due to the amount of energy required, but now a team of researchers at the CUNY Graduate Center's Advanced Science Research Center in New York City has managed to achieve the seemingly impossible by sending a broadband signal into a metal strip filled with electronic switches.By triggering the switches, the scientists were able to double the impedance and thus produce a time reflection.

"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," said study co-author Gengyu Xu.

"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."

It is hoped that the research will help to build improved wireless communications and computer systems.

"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," said co-author Andrea Alu.

Source: Popular Mechanics

Tags: Time