Size of the observable universe
Pro Research Analysisby 
Searched over 200M research papers
Observable Universe Size: Radius and Diameter
The observable universe is defined by the maximum distance from which light has had time to reach us since the beginning of the cosmos, due to the finite age of the universe and the ongoing expansion of space. This creates a horizon beyond which we cannot see, marking the limits of the observable universe 1810.
Recent calculations, using updated cosmological parameters from the Planck satellite, estimate the radius of the observable universe to be about 46.27 billion light-years. This value is slightly smaller (by about 0.7%) than previous estimates based on earlier cosmic microwave background (CMB) data 12. The diameter, therefore, is approximately 93 billion light-years .
Methods for Calculating the Observable Universe's Size
The size of the observable universe is determined by tracing how far light could have traveled since the Big Bang, factoring in the expansion of space. The Hubble constant, which measures the universe's expansion rate, is a key parameter in these calculations. Improved measurements of the Hubble constant and other cosmological parameters have led to more accurate estimates of the universe's age and size 1210.
Some models treat the observable universe as the surface of a 3-sphere, leading to a simple formula for its radius. This approach also finds a radius of about 46.27 billion light-years, matching accepted figures .
Volume and Scale of the Observable Universe
The volume of the observable universe is much larger than the Hubble volume, by a factor of about 12π, according to geometric models . The number of atoms within the observable universe is estimated to be around 10^80, highlighting the immense scale involved . The difference in scale between elementary particles and the observable universe is about 10^40 .
The Universe Beyond the Observable
It is important to note that the observable universe is only a portion of the entire universe. The universe itself may be much larger, possibly infinite, but we can only observe the region from which light has had time to reach us 568. The actual shape and total size of the universe remain unknown.
Observability and Theoretical Considerations
In principle, the size of the universe could be observable if the universe has certain topological properties, such as being multiply connected, which could affect the spectrum of signals detected by certain experiments . Theoretical models also link the size and age of the universe to fundamental physical constants, with some predictions matching observed values within a reasonable margin .
Conclusion
The observable universe has a radius of about 46.27 billion light-years and a diameter of roughly 93 billion light-years, based on the latest cosmological data. This vast region contains an estimated 10^80 atoms and is only a fraction of the potentially much larger, or even infinite, entire universe. The size of the observable universe is determined by the age of the universe, the speed of light, and the expansion of space, with ongoing research refining these measurements as our understanding of cosmology improves 12610.
Sources and full results
Most relevant research papers on this topic