A photon with an estimated energy of around 300 trillion electron volts (TeV) was detected by the Carpet detector at the Baksan Observatory in the Russian Caucasus. This photon is linked to a gamma-ray burst called GRB 221009A, nicknamed BOAT, which means "Brightest Of All Time." This event was observed on October 9, 2022, by space-based instruments Swift and Fermi-GBM. The burst originated from a galaxy located about two billion light-years away, as determined by its redshift, a measure of how much the universe has expanded since the light was emitted. Gamma-ray bursts are among the most energetic explosions in the universe, and high-energy photons like the one detected should, according to current models, interact with the cosmic microwave background (CMB) — the afterglow of the Big Bang — and be absorbed. This interaction typically produces an electron-positron pair, which would prevent the photon from reaching Earth. The probability of this absorption depends on the photon's energy and the distance it has traveled. However, this newly detected photon appears to have bypassed this expected absorption, raising questions about our current understanding of how high-energy photons travel through space. To explain how such a high-energy photon could reach Earth, researchers are considering new theoretical models. Giorgio Galanti, a lead researcher at the Italian National Institute of Astrophysics (INAF), noted that the findings from the Carpet experiment suggest that existing explanations are no longer sufficient. Galanti and his team are investigating the possibility of ultralight particles known as axion-like particles (ALPs), which could allow photons to transform into these particles and back again, altering their propagation. Another possibility is a violation of Lorentz invariance, a fundamental principle in Einstein's theory of special relativity that states the laws of physics are the same for all observers regardless of their motion. Some models of quantum gravity propose that Lorentz invariance might not hold at extreme energies or distances. If true, this could change the way photons interact with the CMB, making the universe more transparent to high-energy radiation. This would allow photons with energies like the one detected to travel farther without being absorbed. Researchers are also analyzing a one-hour delay between the high-energy photons detected by Carpet and those observed by the LHAASO experiment in China. This delay aligns with some scenarios of Lorentz invariance violation, though it is not definitive proof. The findings, detailed in a preprint on the arXiv platform, highlight the need for further study to understand the nature of this extraordinary photon and its implications for physics.