The Universe can outrun light without breaking Einstein’s rules

Date: July 25, 2026 Source: Universe Today Summary: Cosmic expansion allows distant galaxies to move away faster than light, while still letting us see ancient light they emitted when they were much closer. Eventually, accelerating expansion will push nearly every galaxy beyond our Local Group out of sight, making the Universe appear almost empty. Share: Facebook Twitter Pinterest LinkedIN Email FULL STORY The expanding universe is slowly carrying nearly every distant galaxy beyond the reach of light and, eventually, beyond our view forever. Credit: NASA's Goddard Space Flight Center An expanding universe makes measuring distance more complicated because space does not remain fixed while light travels through it. Galaxies continue to emit light, but that light may spend billions of years crossing the cosmos before reaching us. During that journey, the universe keeps expanding, increasing the average separation between galaxies (yes, I know that sometimes galaxies can collide, but we're talking on average, at big scales here). This means that when a telescope captures the light from a distant galaxy, the image does not reveal where that galaxy is today. It shows the galaxy as it appeared when the light began its journey. To estimate its present distance, astronomers must use a cosmological model that accounts for how the universe has expanded over time. The leading model used today is called LCDM. It includes dark matter (different episode) and dark energy (different episode). The strengths and limitations of LCDM are worth discussing separately (different episode), but alternative models do not significantly change the overall picture described here. The Edge of the Observable Universe The universe is about 13.77 billion years old, but the most distant regions we can observe are now roughly 45 billion light-years away. Space expanded during the entire time that their light was traveling toward us. This boundary is known as the particle horizon, the cosmological horizon, or the comoving horizon, depending on how stylish you feel in the moment. It defines the outer edge of our observable bubble and marks the greatest distance we can see today. At first, the numbers seem contradictory. How can the observable universe extend 45 billion light years when the universe is only 13.77 billion years old? The answer is that the universe can expand faster than light. Why Faster Than Light Expansion Is Allowed This does not violate the laws of physics. The speed of light limits how quickly objects can move through space in a local region.