Laura Baudis – TRANSCRIPT
How often do you find time to gaze into the stars?
Last February, I spent a few cold days high up on a mountain, here, in Switzerland, and when I looked out at the sky in a dark, clear night, I saw thousands of glimmering light sources and even the extended nebulous band of the Milky Way. This nebula is made of 100 billion stars and forms a spiral system – our home galaxy.
I am sure that everyone of you had at least once such an awe-inspiring experience. We cannot easily see the entire structure of the Milky Way for we are part of it. We, together with our Solar System, are located in the stellar disc, and we move around the Galactic Center with 220 kilometers per second. But to give you an idea, it would look very much like our close neighbor, the Andromeda Galaxy.
You can see here its beautiful, spiral arm structure, but you cannot see such an image with the naked eye. With today’s advanced telescopes, we can map not only Andromeda in the Milky Way but our entire observable universe in many different wavelengths from radio waves to the very high-energy gamma rays gathering information through the observation of electromagnetic radiation. We can produce countless, beautiful, and useful pictures of the cosmos. Today, we also know that what we see is not the whole picture.
In fact, why would we even assume that what we can directly observe is all that there is? History has overthrown our most basic assumptions many times, it has told us that the Earth is not at the center of the Solar System, that our Sun is at the outskirts of the Milky Way, and that our own galaxy is but one in two trillions of galaxies in the observable universe. That’s why would matter that radiates or that absorbs electromagnetic radiation be the dominant form of matter in the cosmos.
It was back in 1933, when a Swiss-American astronomer, Fritz Zwicky, discovered that something strange was going on in a rich cluster of galaxies, the Coma Cluster. He studied the motion of individual galaxies in this cluster and found out that their speeds were far too high that galaxies should simply fly apart. The speeds were much higher than predicted, based on the luminous matter alone. He concluded that there must be some new form of matter that he called “dark matter,” and which, like a glue, keeps all these galaxies in the cluster together. Zwicky was brilliant and very much ahead of his time, but he was not an easy person to get along with.