Hydrogen wall darkens the sky at night

A 200-year-old hypothesis that the reason the night sky is dark is because hydrogen clouds block out the light from countless stars has been proven correct.

The reason the sky turns dark at night may be because hydrogen clouds block out light. Photo: Olli Henze.

A new study using images from the Hubble Space Telescope proves that a theory that scientists have ignored for 200 years about why the night sky is dark is actually correct, Independent reported today.

Heinrich Olbers (1758 - 1840), a German astronomer, is the one who proposed the famous "dark sky paradox". Accordingly, he questioned why if there are countless stars in the universe, every point in the sky has a star, then it turns dark at night. Olbers speculated that it is because hydrogen clouds block the light.

Astronomers at the time estimated that there were 100-200 billion galaxies in the observable universe, not enough to fill the sky. Therefore, they believed that this hypothesis was not accurate in explaining the reason why the sky turned dark.

However, recently, using the Hubble telescope, astronomers concluded that there are about 2,000 billion galaxies in the universe.

"That 10 times or more number of galaxies could fill the sky with stars, but most or all of the light from distant galaxies would be absorbed by the layer of hydrogen gas between Earth and the galaxy. That was the idea proposed by Olbers, but scientists had previously dismissed it. Now, we're reintroducing this hypothesis as an explanation for the phenomenon of dark skies at night," explained Christopher Conselice, professor of astrophysics at the University of Nottingham, UK.

Professor Conselice said other astronomers had proven the existence of hydrogen clouds by studying the spectrum of light. However, they did not know that there were galaxies behind the hydrogen wall. In addition, some galaxies are so far away in the universe that their light cannot reach Earth.

"There may still be more universes, more objects beyond the horizon, the limit of what we can see," said Professor Conselice.

According to VNE