Why is space dark when the sun shines on the earth?

When the sun is at its zenith during midday, we are bathed in dazzlingly bright light. The more hours that pass, the weaker the light conditions become before night finally arrives with its pitch-black darkness.

But why does space appear to us as such a gloomy entity during the night hours? Because of the thousands and thousands of cosmic light sources that adorn the firmament, the question quickly arises whether the night sky should not be radiantly bright.

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The Olbers paradox

Because of this natural feature, it appears to us on Earth that the sun moves across the sky during the day, and once the sun has disappeared over the horizon, we are deprived of our natural source of light. If the universe is infinitely large and has a uniform distribution of stars, wouldn't the night sky have to shine as brightly as our sun?

After all, there are estimated to be up to 400 billion of these in our home galaxy alone, the Milky Way. astronomer Johann Kepler became suspicious about this very topic in the early 17th century.

The scientists saw in the nocturnal darkness clear evidence that the universe could not be infinite. The great cosmic enigma was to keep the scientific community spellbound in the decades that followed.

The explanations Heinrich Wilhelm Olbers brought into the field concerning this topic became known afterward as the Albers paradox. It refers to world models that follow a perfect cosmological principle.

In simple terms, this means that the universe always appears the same to the observer-independent of his point of view and direction of observation. In the galactic context, this means that an infinitely extended universe must have a uniform distribution of stars, no matter from which direction.

The light of every star, no matter from which direction, would have to hit the earth sooner or later. Consequently, the night sky would have to be as bright as the surface of a star A nightly view of the firmament proves to us, however, that this is not the case.

Why is Space dark?

In his research, Olbers eventually concluded that the gases between stars absorb the emitted light, allowing the light paradox in space to be reconciled with the theory of an infinitely large universe. However, as we now know, if starlight shone on the gas, it would heat up and eventually begin to shine brightly. to the original assumption, the distribution of stars within space is not uniform.

Specifically, the sparkling celestial bodies accumulate in galaxies which in turn form large clusters of galaxies. The basic cosmological principle remains that as soon as our view wanders to the firmament, we are always seeing the surface of some star in an infinite cosmos.

However, we should keep in mind that the average distance between our blue home planet and the glistening bright celestial bodies is simply gigantic This galactic average value is quantified with 10 to the 23rd power or 100 trillion light-years.

Remember, a light-year describes the distance that light covers in a vacuum during one year. While light beams cover 180 000 miles in a single second, they bridge a fantastic distance of nearly 6 trillion miles in one year. This leads to the opposite conclusion that the light of an average star requires 10 to the 23rd power years to cover this enormous distance.

Invisible light particles

Does this mean, then, that terrestrial night will be accompanied by a dazzling brightness sometime in the distant future? No, for by the time we reach that galactic point in time at which we can survey a sufficiently large part of the cosmos, all the stars in the universe would have gone out long ago, for just as in the case of all the other celestial bodies that grace space, stars are finite entities.

The nuclear reaction of the sparkling objects lasts only a relatively short time. At least not in all spectral ranges, the night sky is not as dark as it appears to our earthly gaze.

In reality, the earth is hit from all directions by weak radiation an inch or one millimeter, so they fall into the microwave range. This background radiation represents a remnant of the big bang, a phenomenon that can be proven today and which is significant to current research.

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About 380 million years after the birth of the universe, the temperature in the universe sank to about 5400 degrees Fahrenheit.

In other words, the cosmos became permeable to electromagnetic radiation at that time. Those light particles that were released at that time still present themselves to us today in the form of cosmic microwave background radiation.

As a result of the continuing expansion of the universe, this primeval radiation has lost a large part of its original power. The cosmic background radiation has only one billionth of its former intensity.

Originally, the universe was brightly illuminated by the influence of this background radiation. However, since the wavelength of this galactic relic has shifted from the visible spectrum to the microwave range throughout millions of years, we can no longer detect cosmic background radiation with our human eyes today.

A limited view

We, humans, are only capable of perceiving a fraction of the existing light spectrum. If we were allowed to perceive the infrared in the microwave range, the universe would appear to us in a completely different shape.

Experts are convinced that the baryonic matter visible to us is only a very small percentage of the total matter in the universe. In essence, this proportion is estimated to be only 4.9 percent in the most recent models.

Although the existence of dark energy and dark matter has yet to be experimentally proven, researchers are certain that they play a dominant role within galactic constellations and processes.

Thus, hypothetical dark energy can explain the unexpectedly accelerated expansion of the universe, and the movements of visible matter can be classified with the help of dark matter. This expansion process has persisted to the present day.

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