Why is the Sky Dark at Night?
When I asked my wife why the sky is dark at night, she said, “It’s because the sun’s not shining!” Yet generations of astronomers have struggled to answer this question. It’s become known as Olbers’ Paradox. Although it’s one that few spend time thinking about, for cosmologists it’s always been important.
The darkness of the night sky was one of the earliest observations that cosmologists could use as a basis for developing an understanding of the universe. In theory, they knew that even at night the sky should shine like a curtain of light. Explaining why it didn’t helped cosmology to be seen as a true science that is based on observation rather than speculation. It was one of the first observations that helped us realize that the universe is not infinite either in age or extent.
To light the sky from horizon to horizon with starlight would require trillions more stars than now exist. Alternatively, we’d have to be able to look back in time longer than the universe has existed. The universe is not old enough or big enough to have a bright night sky. As we look beyond the galaxies and quasars, we detect only the background cosmic radiation left as a remnant from the moment of creation, when the sky really did blaze.
So next time you gaze at the night sky, remember you’re seeing a puzzle, whose explanation has helped us understand the universe.
Sometimes what we don’t see is as telling as what is present. We look for evidence of what is there, but equally important is what is absent or lacking. This is negative evidence, but evidence nonetheless.
A friend of mine is a fairly good artist. When she was learning to draw, she was rather inept. She had a desire to draw, but little training in it. She often was dissatisfied with her work. Yet by the time I met her, she was a respectable amateur. Her after school activities with her children included story telling and always a sketch to go with it for them to imitate or to colour on their own.
My own skills are remarkably inadequate in comparison. I would have to draw something first, decide what it was and then construct some story to go along with my ‘artwork.’
One day I asked my friend how she was able to sketch so well. She replied that when she was in the early stages of skill development, an artist suggested that she draw not what was there, but rather what was absent: not the table but the space around the table. “Outline the air underneath the furniture. Look at the space between the legs. Draw these, rather than the table top and the table legs.” When my friend shifted her focus from what was there to what was missing, she made incredible strides in her artistic talents. She began looking at the absent rather than the present. Her change in perspective gave her abilities to accomplish what she had wanted to do from the outset.
There has been much debate over the history of humankind about the existence of a divine being. Arguments have been made for and against God. These typically are based in philosophy, logical reasoning, scientific evidences in creation and the nature of mankind. Today, for example, we talk about Intelligent Design in creation - how unlikely that everything (from quirks to quarks to quasars) came to be as it is by chance. Thinkers of earlier ages considered that creation must have a Creator, that which is caused must have a Cause, that which moves must have a Mover.
These arguments challenge us to wrestle with the idea of the existence of God. However, one thing we cannot logically do is to argue from the negative. We can’t prove that God doesn’t exist. Think about that statement for a minute. How would you go about proving that God doesn’t exist? The best that you could do is to argue against the positive evidences for His existence. Consider the evidence.
Dr. David Humphreys and Debbie Hughes
© August 2004
