Why the universe looks black

Look at the night sky or find pictures of the universe on the Internet, and you will see the same thing: the inky, infinite blackness of the universe, interspersed with bright stars, planets or spacecraft. Why isn’t the universe as vivid as the blue daytime sky on Earth?

“You’d think that since there are billions of stars, billions of galaxies in the universe and other objects in our galaxy, like planets that reflect light – that when we look at the sky at night it should be extremely bright. But instead, it’s really dark.” states Tenley Hutchinson-Smith, a graduate student in astronomy and astrophysics at the University of California.

Hutchinson-Smith explained that this contradiction, known in physical and astronomical circles as the Olbers paradox, can be explained by the theory of space-time expansion – the idea that “as our universe expands faster than the speed of light, light from distant galaxies may stretch.” and converts into infrared waves, microwaves and radio waves, which our human eye cannot detect. ” And because they can’t be seen with the naked eye, they look dark.

Another reason why interstellar and interplanetary space seem dark is that the universe is an almost perfect vacuum. Let us remind ourselves that the Earth’s sky is blue, because the molecules that make up the atmosphere, including nitrogen and oxygen, scatter many wavelengths of the visible component of light blue and purple waves from the Sun in all directions, including the direction to our eyes. Since the universe is an almost perfect vacuum – which means that there are extremely few particles – there is practically nothing in the space between the stars and the planets that would scatter light to our eyes. And when the light does not reach the eyes, we see black.

Nevertheless, a 2021 study in the journal Astrophysical Journal suggests that the universe may not be as black as scientists originally thought. Through NASA’s New Horizons mission to Pluto and the Kuiper Belt, researchers were able to see the universe without interfering with light from Earth or the Sun. The team cleaned up the images taken by the spacecraft and took away all the light from the famous stars, the Milky Way and possible galaxies, as well as all the light that could have leaked from the miracles of the camera.

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