recent – Henning Raach

Farewell to Darmstadt

Another part of my life came to an end in October. Writing about it puts the question in which attitude I do it. I want to write thankfully. In 2009, I came to Darmstadt. First I worked at the Technical University, then at the accelerator GSI. I wrote a monography. For 10 years I took part in the workshop band of Jürgen Wuchner who died in 2020. Eight times I participated in the Jazz Conceptions, a one week summer workshop. I enjoyed the vibrant music scene, especially the concerts at Jazz Institute and at Knabenschule. The Frankfurt Radio Big Band played at Centralstation. Darmstadt also has a Staatstheater (public theatre) with opera. Each summer the Jürgen Wuchner Workshop Band gave a promenade concert in Orangerie Garden if it did not rain. I feel sad that I had to leave friends. Certainly will I return as a visitor.

Climate Change

At present the Corona crisis is very severe. Many people die from the virus. The damage to the economy is huge. Nonetheless, I want to write on another problem of mankind, the climate change. I have read a German book on this subject by two climatologists from Potsdam, Rahmstorf and Schellnhuber. They report on a large consensus in science that the global warming is caused by man. Doubling the amount of carbon-dioxide in the atmosphere would mean a temperature rise of 3 Kelvin (+/- 1 K at a confidence level of 95%.) Those who want to know more are advised to read the reports of the IPCC (Intergovernmental Panel on Climate Change.) I think their scientific arguments should be taken seriously, as well as their concern to use the knowledge of our time in a responsible way.

Black Hole

Recently scientists succeeded in taking a picture of a black hole. Therefore, I want to write a few lines about this phenomenon.

In a black hole, matter is so highly compressed that even light cannot escape from its vicinity. General relativity treats a black hole as a point, i.e. it has no extension. This is hard to imagine. However, take as an example the electron which is considered as a point particle, although it has a mass at rest.

A black hole is surrounded by an event horizon. Everything that passes it becomes invisible for the world outside. If a matter-antimatter pair is created from the vacuum near the event horizon, a particle may cross it. The other particle seems to come out. This is Hawking radiation.

In particle physics, there are collisions at high energies. Can a black hole be produced in a collider experiment? This question was subject of a court dispute. The physicists bring forward the argument that the cosmic radiation contains particles of much higher energy. Although the cosmic radiation hits the Earth, our world still exists.