The universe's expansion allows distant regions to move apart faster than light, creating a complex relationship between the age of the cosmos and the size of the observable universe.
Key facts
- •The universe is estimated to be 13.77 billion years old.
- •The observable universe extends to a radius of roughly 45 billion light-years.
- •The Hubble distance, where galaxies recede faster than light, is approximately 13.77 billion light-years away.
- •The cosmological event horizon is currently about 17 billion light-years away.
- •In about 100 billion years, galaxies outside the Local Group will fade from view.
While the universe is approximately 13.77 billion years old, the most distant observable regions are roughly 45 billion light-years away. This discrepancy exists because space itself expands, allowing galaxies to recede from one another faster than the speed of light. This phenomenon does not violate Einstein's laws of physics, as the speed of light limit applies to objects moving through space, rather than the expansion of space itself.
By the numbers
Measuring Distant Galaxies
Because space expands while light travels, images captured by telescopes show galaxies as they appeared when the light was emitted, not where they are today. Astronomers use the LCDM cosmological model to estimate current distances, accounting for the expansion of the universe over time. The speed at which a galaxy recedes is measured via redshift, where light is stretched toward redder wavelengths as the galaxy moves away.
Cosmological Horizons
The 'Hubble distance,' located about 13.77 billion light-years away, marks the point where galaxies begin receding faster than light. Beyond this, the 'cosmological event horizon'—currently about 17 billion light-years away—represents a boundary where light emitted today will never reach us due to the accelerating expansion driven by dark energy. This horizon is expected to reach a maximum distance of about 60 billion light-years.
The Future of Observation
In approximately 100 billion years, light from galaxies beyond the Local Group will be stretched to such extreme wavelengths that they will effectively disappear from view. Future observers will perceive a universe that appears significantly smaller and emptier than the one visible today.
Advertisement
This article was independently rewritten by ManyPress editorial AI from reporting originally published by ScienceDaily.
