Olbers’ Paradox
In 1826 Heinrich Wilhelm Matthäus Olbers (German physician and astronomer, 1758–1840) realized that if the universe is unlimited, every line of sight from Earth should end on the surface of a star. No matter how many stars the line missed, eventually there would be one in the way. The whole daytime and nighttime sky should always be as bright and hot as the surface of an average star. The effect would be like having the sky packed solid with many copies of our Sun. The fact that the stars are much farther away than our Sun makes no difference because the Earth has had time to come to equilibrium temperature with them. The Earth’s temperature should be like the Sun’s, 10 000º F or 6 000º C. At such elevated temperatures life on Earth would be impossible. Life based on atoms requires very complex compounds of atoms, but even the simplest compounds of two or three atoms break up at such high temperatures. We should be burned far worse than a crisp.
But we are not roasted, and the night sky is dark. This contradiction is called Olbers’ paradox. Olbers did not know of the expansion in the heavens that cools the light. Hubble discovered that in 1929. Neither did Olbers know that the universe was created a finite time ago. The age of the universe was not known until recently. These two factors, the expansion and the limited age of the universe, keep the sky cold.
The finite age of the universe makes it impossible for us to see beyond a certain limit. We run out of previous time before we run out of space. The limit we can see is not the edge of the universe, but the beginning. Some lines of sight stop when they reach the surfaces of stars, but many lines of sight stretch back to times long before the stars.
The darkness of space is now cold. It is far less energetic that the darkness of the first night. The beginning and the expansion caused the present darkness of space. Let’s try to understand this from a simple example.
But we are not roasted, and the night sky is dark. This contradiction is called Olbers’ paradox. Olbers did not know of the expansion in the heavens that cools the light. Hubble discovered that in 1929. Neither did Olbers know that the universe was created a finite time ago. The age of the universe was not known until recently. These two factors, the expansion and the limited age of the universe, keep the sky cold.
The finite age of the universe makes it impossible for us to see beyond a certain limit. We run out of previous time before we run out of space. The limit we can see is not the edge of the universe, but the beginning. Some lines of sight stop when they reach the surfaces of stars, but many lines of sight stretch back to times long before the stars.
The darkness of space is now cold. It is far less energetic that the darkness of the first night. The beginning and the expansion caused the present darkness of space. Let’s try to understand this from a simple example.
