The observed darkness of the night sky confirms that the universe is not infinite and eternal, according to a France Inter podcast.
This astronomical realization resolves a long-standing contradiction known as Olbers’ paradox. If the universe were eternal and static, every line of sight from Earth would eventually hit a star, making the entire sky as bright as the sun.
Heinrich Olbers, a 19th-century astronomer, first formulated the paradox to question why the night remains dark. The solution lies in the fact that the universe has a finite age and is continuously expanding. Because of this expansion, light from the most distant stars has not yet had enough time to reach Earth.
Presenting the concept on the podcast "C'est prouvé," Fabrizio Bucella said that the current age of the universe is approximately 13.8 billion years [1]. This time limit means there is a cosmic horizon beyond which light cannot reach observers on Earth, creating the gaps of darkness seen between stars.
Furthermore, the expansion of space stretches the wavelength of light traveling from distant galaxies. This process shifts visible light into the infrared spectrum, rendering it invisible to the human eye. The combination of a finite starting point and the stretching of space prevents the sky from becoming a solid wall of light.
These factors prove that the universe is not a steady-state system but one with a specific beginning. The darkness of the night is not an absence of stars, but a marker of the distance and time that separate Earth from the furthest reaches of the cosmos.
“The night sky is dark because the universe has a finite age.”
The resolution of Olbers' paradox provides critical empirical support for the Big Bang theory. By demonstrating that the universe has a beginning and is expanding, astronomers can move away from the 'steady-state' model, which incorrectly assumed a universe without a start or end date.
