At the end of the 18th century, German astronomer Heinrich Olbers made an assumption on the paradox, which later became known as “Olbers’ paradox“:
• The age of the Universe is infinite;
• The extent of the Universe is infinite;
• Stars are evenly distributed throughout the Universe.
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That is, looking at the night sky, one could observe billions of stars. This is endless starlight, a brightly lit sky in all directions.
The assumptions of Olbers seemed very worthy during that time. But today, science has made much progress.
Firstly, the universe is not infinitely old. It is only 13.8 billion years old. Secondly, the universe is not infinite. Its diameter is 93 billion light-years. It extends to the visual limit. A person simply can’t observe anything beyond the available horizon, so the number of stars that can be seen is limited.
If you add the total number of objects tending to infinity, then, in the end, you can get the final result.
For example, consider a simple circle that will be filled with dots. The smaller the size of the point is, the more they fit in a circle. That is, you can place a lot more grains of sand than billiard balls. Pay attention to the photo below.
Surely, you have noticed that from the point of view of an observer, the dimensions of the Sun and Moon are close. But in reality, the Sun is 400 times wider than the Moon.
The thing is that the farther the object is, the smaller it looks. The sun is 400 times farther from us than the moon, so they look the same in size.
For us, the next nearest star is in Alpha Centauri, which is 10 times larger than the Sun. It should appear 10 times brighter than the Sun to us, but the radius of the biggest stars in the observable universe is only in a size of 2600 solar radii.
Even if you put the biggest star in the universe in place of Alpha Centauri, for us, it would be only 1% brighter than the sun. The following item is directly related to this.
Thirdly, stellar light fades with increasing distance. Very distant stars are not visible to the eye and detecting them is even difficult for the most sensitive devices.
Fourth, in the entire Universe, there is a huge amount of accumulations of gas and dust that obscure the light of stars passing through them.
There is a very large number of stars in the sky. The vast majority of them are so small and emit so little light on the Earth that they are not visible to the naked eye at all.