Recent discoveries in physics and astronomy have deepened the understanding of the causes of darkness in the universe around us more than expected (Pixaby)
As daylight fades at dusk, a dark starry canvas unfolds above our heads. But this familiar night shift from bright blue to velvet black skies arouses the curiosity of astronomers and philosophers; if the universe contains a sea of stars spanning an infinite number of light-years, why can't the night sky be as bright as the day?
The answer to this question may seem simple, but it has puzzled scientists. It's actually a famous cosmic problem that has preoccupied scientists for two centuries, and it took a long time to find the right answer, which is known today as the Uber paradox.
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The Olber paradox baffles scientists
If you walk through a small grove of trees and look away, you can see parts of the horizon among the logs around you. If you stand in the middle of a large forest, your view is completely obscured in all directions by the huge number of logs that surround you from all sides and at varying distances.
O'Per thought the universe was infinite, but it turned out not to be limited in its lifespan of about 13.8 billion years (Pixels).
Similarly, if the universe is large enough, your line of sight should be obscured in every direction by a thick wall of stars that make night as bright as day.
The story of the Olber paradox takes us back to the early nineteenth century, to a German astronomer named Heinrich Olber, who was the first to spread this paradox in the scientific community, although scientists such as Johannes Kepler and Edmund Halle had preceded him. O'Ilper's question revolved around the apparent contradiction of a night sky full of infinite stars and the darkness we observe: if the universe is endless and filled with an infinite number of stars, then every line of sight must eventually end at a star, making the night sky uniformly shining.
However, the night sky is not a bright tapestry of infinite stars, dominated by pitch darkness and punctuated only by light for distant stars and galaxies. To understand this, we need to dig deeper into the concepts of the age and expansion of the universe.
How did scientists solve the problem?
Olber thought the universe was infinite, but it turned out not to be, limited in its lifespan of about 13.8 billion years. So we only see objects as far away as the distance light was able to travel during this time, limiting the number of stars that can be seen, and therefore the amount of starlight reaching us.
The vastness of the universe makes much of the starlight shift from the visible spectrum into wavelengths that cannot be seen by the eye (Shutterstock)
Part of the solution to the Ober's paradox also lies in the expansion of the universe: In the early twentieth century, astronomers, including Edwin Hubble, made groundbreaking observations that showed that other galaxies were rapidly moving away from our own. This suggests that space-time itself is expanding. Because of this amplitude, light waves from distant stars expand as they travel through space, and the greater the light journey, the longer its wavelength, a physical phenomenon known as redshift. This redshift means that much of the extragalactic starlight is shifted from the visible spectrum into infrared wavelengths that cannot be seen by the human eye.
Other evidence of the cause of the darkness enveloping Earth at night has emerged in the cosmic microwave background radiation discovered in 1964 and represents the glow of heat remaining from the early stages of the universe's birth from the Big Bang. After the initial explosive expansion, the universe cooled as it continued to expand, eventually causing light to separate from matter, and photons were able to flow freely through space like the cosmic microwave background radiation we observe today. If we look at space in the microwave part of the spectrum, we can actually find it illuminated in all directions.
Darkness in the universe is not a vacuum
Another problem with the interpretation of the dark night sky involves distinguishing between the observable universe and the entire universe, as the visible universe represents only the small spherical region of space that enables light to reach us during the life of the universe.
Dark matter hides light sources in the universe (Pixaby)
Interestingly, recent discoveries in physics and astronomy have deepened the understanding of the causes of darkness in the universe around us more than expected. Observations of galaxies and supernovae have revealed the presence of dark matter and dark energy that make up more than 95% of the universe.
Scientists define dark matter as an invisible mass discovered only by gravity that binds galaxies together, while dark energy is mysterious energy that accelerates cosmic expansion, both of which hide light sources within the universe.
Although the blackness of the night sky seems empty, it actually tells in minute detail the history of the darkened universe from explosion to cooling and expansion. When we look at the night sky, we glimpse the paths of cosmic evolution stretching through the void in deep space.
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Sources:
Source : Al Jazeera + Agencies