The observable universe spans approximately 93 billion light-years across. Despite the universe being roughly 13.8 billion years old (some estimates place it at 13.77 billion years), the vast distances involved are governed by the expansion of space itself.
Space continued expanding as light from the oldest sources traveled toward us. Currently, the most distant regions we can observe are located roughly 45 billion light-years away from Earth.
The total width of the observable universe.
The Mechanics of Cosmic Expansion
The boundary defining the limits of what we can see is known as the particle horizon. Scientific principles state that while the speed of light limits how fast objects can move through space locally, cosmic expansion can exceed that speed because it involves the expansion of space itself rather than motion through it.
Astronomers determine the recession speeds of galaxies by measuring redshift. Edwin Hubble utilized these measurements to uncover evidence that the universe is expanding.
Edwin Hubble used redshift to uncover evidence that the universe is expanding.
The specific point at which galaxies begin receding faster than light is identified as the Edwin Hubble distance. This threshold is currently located about 13.77 billion light-years away.
The Edwin Hubble distance where galaxies begin receding faster than light.
We can still observe galaxies beyond the Edwin Hubble distance because their light was emitted when they were significantly closer to our location.
The Limits of Observation
There is a definitive limit known as the cosmological event horizon, currently estimated at approximately 17 billion light-years. Light emitted from beyond this boundary today will never reach us.
The current cosmological event horizon.
Projections suggest the cosmological event horizon will eventually reach a maximum distance of about 60 billion light-years.
In approximately 100 billion years, every galaxy beyond the Local Group will fade from human sight forever. This acceleration is driven by dark energy, which makes the separation caused by expansion increasingly extreme.