Look at the night sky with your own eyes, or marvel at the images of the universe on the Internet, and you will see the same thing: deep dark space dotted with bright stars, planets or spaceships. But why is it black? Why is space not colored, just like the blue sky in the daytime on Earth?
Surprisingly, the answer has nothing to do with insufficient light.
“Some people would think that since there are billions of stars in our Milky Way, billions of galaxies in the universe, and other objects, such as planets, all reflect light. When we look up at the sky at night, it will be very brilliant. .,” Tenley Hutchinson Smith, a graduate student in astronomy and astrophysics at the University of California, Santa Cruz (UCSC), told Live Science in an email. “But instead, it’s actually very dark.
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HutchinsonSmith said that this contradiction, known as the Olbers paradox in the circles of physics and astronomy, can be explained by the theory of the expansion of space-time, this idea “because our universe is expanding faster than the speed of light … light from distant galaxies can be stretched out into infrared, microwave, and radio waves, which are invisible to our human eyes, and because they cannot be detected, they appear dark (black) to the naked eye.
Miranda Apfel is also a graduate student in astronomy and astrophysics at UCSC, and agrees with HutchinsonSmith. “Stars emit light in various colors, even colors that are invisible to the human eye, such as ultraviolet or infrared,” he said. to Live Science “If we can see microwaves, all space will emit light.” Apfel said this is because the cosmic microwave background (the light energy of the Big Bang scattered by protons and electrons). thrones in the early universe) still fills all space.
Another reason why interstellar and interplanetary space appear dark is that space is almost a perfect vacuum. Remember that the earth’s sky is blue because the molecules that make up the atmosphere, including nitrogen and oxygen, scatter large amounts of blue and purple wavelengths of visible light from the sun in all directions (including our eyes). However, in the absence of matter, light travels in a straight line from the light source to the receiver. Since space is a nearly perfect vacuum, which means it has very few particles, there is hardly anything in the space between stars and planets that can scatter light into our eyes. No light reaches the eyes, what they see is black.
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Having said that, a 2021 study in the Astrophysical Journal showed that space may not be as dark as scientists initially thought. Through NASA’s New Horizons missions to Pluto and the Kuiper Belt, researchers have been able to see space without interference from the Earth or the sun. The team examined the images taken by the spacecraft and subtracted all light from known stars, the Milky Way, and possible galaxies, as well as any light that might have been leaked by the camera’s quirks. They found that the backlight of the universe is still twice as predicted. The reason for the added brightness of
is not yet clear and will be the focus of future research. Until then, one thing seems likely: the space is likely more “charcoal” than black.

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