Negative Time

Negative time is a peculiar quirk of quantum mechanics, like the possibility of an object being in two places at one time (think: Schrodinger’s cat) or two particles existing in the same state when far apart (aka quantum entanglement). Quantum mechanics is the world of atoms, electrons, and photons and at times, can appear to be at odds with what we see in the world around us. As for negative time, it refers to a period of time that is less than zero.

The concept was explored earlier this year by scientists at the University of Toronto. As IFLScience reported at the time, researchers released a study on the preprint server arXiv (meaning it is yet to be peer-reviewed) that demonstrates how objects can emit light in so-called negative time. The piece of research involved looking at how long it takes a pulse of light to travel through a cloud of atoms.

As light passes through the cloud, the atoms temporarily absorb the photons, triggering an “excited” state before releasing the photons. The team measured the amount of time atoms remained in this excited state. Curiously, there were instances where the time was negative, i.e. less than zero.     READ MORE...

Negative Time Found

Quantum physicists are familiar with wonky, seemingly nonsensical phenomena: atoms and molecules sometimes act as particles, sometimes as waves; particles can be connected to one another by a “spooky action at a distance,” even over great distances; and quantum objects can detach themselves from their properties like the Cheshire Cat from Alice’s Adventures in Wonderland detaches itself from its grin. 

Now researchers led by Daniela Angulo of the University of Toronto have revealed another oddball quantum outcome: photons, wave-particles of light, can spend a negative amount of time zipping through a cloud of chilled atoms. In other words, photons can seem to exit a material before entering it.

“It took a positive amount of time, but our experiment observing that photons can make atoms seem to spend a *negative* amount of time in the excited state is up!” wrote Aephraim Steinberg, a physicist at the University of Toronto, in a post on X (formerly Twitter) about the new study, which was uploaded to the preprint server arXiv.org on September 5 and has not yet been peer-reviewed.     READ MORE...