The speed of light might have been basically infinite at the start of time before it suddenly slammed on the brakes.
March 23, 2026
Original Paper
A T-Duality-Protected Speed-of-Light Bounce in String Gas Cosmology
arXiv · 2603.19334
The Takeaway
Instead of being a fixed universal constant, this model suggests the speed of light "bounced" from a super-fast phase to a total standstill. This fluctuation could explain why distant parts of the universe look so similar today without needing to rely on the standard theory of 'cosmic inflation.'
From the abstract
We study a varying-speed-of-light (VSL) phase embedded in string gas cosmology (SGC), with the effective propagation speed controlled by the dilaton during the Hagedorn era. For the exponential ansatz $c(\phi)=c_0\,e^{-\alpha\phi}$, the analytic Hagedorn background generates a speed-of-light bounce: an early superluminal phase ($c\gg c_0$), crossover at $t/t_0\approx 0.285$ for the branch studied here, and a collapse of $c$ toward zero as the self-dual regime is approached. The self-dual point a