Quantum physics often challenges our understanding of reality, and a new study led by Daniela Angulo from the University of Toronto adds another mind-bending discovery to the mix: photons, the wave-particles of light, can seem to pass through a cloud of atoms in “negative” time, effectively appearing to exit a material before they even enter it.

Aephraim Steinberg, a physicist from the same university, shared this surprising result on X (formerly Twitter), after the team’s findings were uploaded to arXiv.org in early September. While not yet peer-reviewed, the study reveals that photons interacting with a cloud of ultracold rubidium atoms can appear to spend a negative amount of time in the excited state—a phenomenon that defies conventional expectations.

For nearly a century, dark matter—a mysterious substance believed to account for most of the universe’s mass—has baffled scientists. First hypothesized by Dutch astronomer Jan Oort in 1932 to explain the unseen mass necessary for galaxies to remain intact, dark matter has remained elusive, with no direct detection despite decades of research. However, a recent study by Dr. Richard Lieu of The University of Alabama in Huntsville (UAH) proposes a groundbreaking alternative that could shift our understanding of cosmic forces.

In his paper, published in the Monthly Notices of the Royal Astronomical Society, Dr. Lieu introduces a revolutionary theory suggesting that gravity might exist without the presence of mass. If correct, this theory could explain certain gravitational phenomena without the need for dark matter.