Time can flow in the opposite direction, but only for photons

Is it possible to leave the room before entering it? It may seem like a crazy idea, but in negative time it might be possible, at least for photons.

In one Published study Recently, a group of researchers from the University of TorontoHe claims to have observed photons exiting a substance before entering it. It’s the first time scientists have found evidence of adverse weather.

“A negative time delay may seem paradoxical, but it means that if you were to build a ‘quantum’ clock to measure how long atoms spend in the excited state, the clock hand would, under certain conditions, move backwards instead of forwards.” Ha announced to American Scientific Josiah Sinclair, a postdoctoral researcher at MIT who previously collaborated with the study’s authors.

Define negative time delay

For the past seven years, the study’s authors have been studying atomic excitation, a phenomenon that occurs as a result of the interaction between light and matter.

During atomic excitation, an atom’s electrons absorb energy from light and move to a higher energy level. However, this increase in energy is not permanent and the electrons soon return to their previous levels and release photons.

This process causes a delay, making it take longer for light to pass through matter than it does when it is absorbed and re-emitted by atoms.

A graph showing negative time

The study authors conducted an experiment to examine this delay (also called group delay) in photons. They fired photons at extremely cold rubidium atoms and studied atomic excitation. The experiment led to a surprising observation.

The researchers noticed that some photons pass through atoms faster than the atomic excitation process can be completed. The result was a negative transit time, making it appear as if the photons exited the material before entering it.

“It sounds silly, I know. It took a positive amount of time, but our experiment observing that photons can make atoms appear to spend a *negative* amount of time in the excited state worked!Ephraim Steinberg, one of the study’s authors and a quantum physicist at the University of Toronto, said: written We are X.

Woo hoo!

It took positive time,
But our experiment that observed that photons can make atoms appear to spend *negative* time in the excited state is over!

I know it sounds crazy, but check it out!
Kudos to Daniela + the rest of the team!https://t.co/rHrAUJq5rX pic.twitter.com/Lz7Lazb1Gs

– Ephraim Steinberg (@QuantumAephraim) September 6, 2024

Adverse weather affects physics, but not us

This experiment was one of the achievements of experimental physics, the branch of physics that studies how to perform experiments that confirm a theory. For example, the device in which photons interact with ultracold rubidium atoms required three years of work.

The results of this experiment “suggest that negative values ​​assumed by times such as group delay have greater physical significance than is generally appreciated,” according to the researchers.

An important point to note is that the photons in the experiment did not carry any information about the nature of time. Therefore, the results of this experiment do not conflict with our understanding of time and photons in context RSpecial theory of relativity.

It will not affect our experience of time thus Concept of time It will continue to remain the same for us.

However, since there is a negative time delay in the case of photons, this will likely affect further research aimed at understanding the details of the quantum world. At this point, it is necessary to delve into whether there are other cases in which time takes negative values ​​and thus moves in the opposite direction.