Does cosmic friction explain dark energy better than Einstein's constant?

Physicists tested whether friction in the cosmic fluid could replace dark energy as the driver of the universe's accelerating expansion. Using measurements from supernovae, galaxy surveys, and the cosmic microwave background, they found that a viscous dark energy model fits observations better than the standard cosmological constant—especially when the fluid interacts with ordinary matter. This suggests dissipation, not just inert vacuum energy, might explain why galaxies are flying apart faster.