Missing Link: The Dark Matter Mystery – The Invisible Elephant of Cosmology

How big is the universe? What is it made of? How did it come about and how did it become as we know it today? Cosmology, the study of the origin and development of the universe, deals with these topics. It is currently one of the most exciting disciplines in natural science, and it spans the physics of the smallest to the largest structures we know. The new series of articles outlines the current state of knowledge and explains why the great majority of cosmologists seem to cling to ideas as absurd as of empty space with repulsive gravity, the emergence of the universe out of nothing and the invisible matter from which 95 percent of the universe is made exist. The first three parts will be about dark matter – the invisible elephant of cosmology.

If you look at the sky in a dark place on a clear, moonless night, you will find a dull, glowing band that spans the entire sky: right through the constellation of Sagittarius, the famous summer triangle of eagle, lyre and swan, Cassiopeia, the Gemini all the way down to Orion, and the circle closes in the southern sky, invisible to our latitudes all year round, over the ship and the Southern Cross back to Sagittarius. This is the Milky Way, our home galaxy, roughly in the shape of a discus with a flat outer area and a thickened, zeppelin-shaped central area (it is a Balken-Spiralgalaxie).

It measures about 185,000 light years, contains several hundred billions of stars and at least as many planets. Viewed from above, it shows 4 arms leading outwards in a spiral shape, which protrude from the otherwise evenly star-studded disc due to young, blue stars. Our sun is on the inner edge of a spiral arm halfway out from the center. It turns majestically slowly around itself; it takes the sun 240 million years to make one orbit. Before the last circumnavigation, the first dinosaurs were just emerging. An island of the world, as hundreds of billions populate the observable universe. But these are apparently just the foam on the waves of a much more powerful ocean.

What is missing: In the rapid world of technology, there is often the time to rearrange the many news and backgrounds. At the weekend we want to take it, follow the side paths away from the current, try different perspectives and make nuances audible.

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Our conception of the universe looked completely different 100 years ago: until the 1920s, a large part of astronomers assumed that the Milky Way formed the entire universe and that the numerous small, often spiral-shaped nebulae in the sky such as the large one Nebulae in the constellation Andromeda are just gas clouds within the Milky Way – otherwise they would have to be partially millions of light-years away, which seemed completely absurd to many. Others believed that galaxies like the Milky Way were galaxies and that the universe was much larger than expected.

When increasingly larger telescopes such as the 2.5 m Hooker telescope on Mount Wilson made it possible to resolve the Andromeda Nebula into individual stars, the dispute among cosmologists called the “Great Debate” was finally resolved in the 1920s: Edwin Hubble succeeded it was possible to determine the distance of the Andromeda Nebula for the first time on the basis of a certain type of variable stars, whose periodic pulsation duration allowed conclusions to be drawn about their luminosity. Because a given luminosity results in a clear brightness for every distance. It came to 900,000 light years, because the period-luminosity relationship of the Cepheid stars was not yet adequately calibrated; today we know it is 2.5 million light years. But a result in the right order of magnitude was a gigantic leap in knowledge that degraded the Milky Way from the rank of embodiment of the entire universe to a speck of dust in the same.

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