Misconceptions About the Universe

The universe’s expansion can make distant galaxies appear to be moving away faster than light without violating Einstein’s special relativity—because nothing is required to travel through space faster than light; instead, space itself stretches. During inflation, the early universe expanded extremely rapidly, which often gets framed as “faster-than-light motion.” That framing misses a key distinction: special relativity bans faster-than-light movement through space, not the recession speeds that arise when the metric of space expands.

Hubble’s late-1920s observations established that recession speed increases with distance: the farther a galaxy, the faster it recedes on average. From that relationship comes the idea of the Hubble sphere, a notional boundary around us where the average recession velocity equals the speed of light. Beyond the Hubble sphere, galaxies recede faster than light relative to us—so it seems like their light should never reach Earth. Yet light from extremely distant galaxies is observed, which is possible because the Hubble sphere is not fixed in size. As space continues to expand, the boundary where recession equals light speed can grow faster than light can “escape” outward, allowing photons emitted in a superluminal region to later find themselves in a subluminal region where they can travel toward us.

This mechanism helps explain why the observable universe is larger than the Hubble sphere. The limit on what can be seen is instead set by the particle horizon, determined by how long light has had to travel since the universe’s beginning. Using an age of about 13.8 billion years, estimates place the observable universe’s radius at over 46 billion light-years and its diameter around 93 billion light-years. Because expansion has accelerated, regions now far beyond 13.8 billion light-years away can still have emitted light that eventually reached us.

The discussion then turns to the Big Bang and the question of what “expanding from a point” means. If the universe were finite, the earliest state would resemble a tiny, dense singularity. But if the universe is infinite—as it may be—the Big Bang would effectively occur everywhere at once, not from a single location. In that case, the universe doesn’t need to expand into something external; it can expand “into itself,” since infinity doesn’t run out of space.

Overall, the central takeaway is that faster-than-light recession is a property of expanding space and the evolving Hubble sphere, not a sign that matter or light is breaking relativity’s speed limit. That distinction resolves a common misconception and clarifies why we can observe galaxies whose recession speeds exceed light speed today.