Raio de Hubble
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
The Hubble radius is a theoretical measure estimating the size of the observable universe. It's calculated by dividing the speed of light (c) by the Hubble constant (H), using the formula rH = c/H. This metric helps understand the scale of the expanding universe and is widely used in cosmology to estimate distances between galaxies and the edge of our observational reach.
The calculator uses c ≈ 299,792 km/s and H ≈ 70 km/s/Mpc (megaparsec) to estimate the radius. However, it's important to note that the Hubble constant's value remains a topic of scientific debate, with different measurement methods yielding varying results. This directly impacts the final calculation accuracy.
This tool is useful for astronomy students, researchers, and enthusiasts wanting to grasp the universe's scale. Still, the Hubble radius doesn't represent a physical tangible limit but rather an approximation based on the cosmos' expansion rate. For practical applications, consider combining results with more comprehensive cosmological models.
Cautions: The Hubble constant may vary depending on data sources (supernovae, cosmic microwave background, etc.). Additionally, the real observable universe (over 90 billion light-years) is larger than the Hubble radius, as it includes light emitted at different cosmic eras.
Frequently asked questions
What is the Hubble radius?
It's the theoretical distance up to which light from celestial bodies can still reach Earth, calculated by dividing the speed of light by the Hubble constant.
How does the calculator work?
It takes light speed and Hubble constant values, applies the rH = c/H formula, and returns estimates in light-years or kilometers.
What is this measure used for?
It helps contextualize the scale of the observable universe and understand the relationship between cosmic expansion and observation limits.
Is the Hubble radius equal to the observable universe?
No. The real observable universe is larger, as it includes galaxies now beyond the Hubble radius whose past-emitted light has already reached Earth.
Why do results vary?
Because the Hubble constant isn't universally agreed upon, varying depending on measurement methods used by scientists.