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.
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.
She is the composer of piano sheet music collections like Enjoy Your Piano and Traumhafte Klaviermusik (Dreamful Piano Music). She masters many styles: classic, Latin, pop, and jazz. One of my favourite pieces is Wie ein Wunder (Like a Miracle):
The title can also be read as A Way From The Blues. I have practised many ways to play the blues and to improvise over the changes. Now, the composition is supposed to have nothing in common with a blues. This year it was performed thrice, the last time in a park in August.
This is a piece from the year 2017 performed at the barbecue of the Jazz & Pop School. The melody consists of an Indian pentatonic. Essentially, this is a minor pentatonic with a major third. I especially like the mysterious, psychodelic intro by the string instruments.
There are materials that have zero electrical resistance if the temperature is sufficiently low. Also the current density and the magnetic field should not be too high. In 1908 Heike Kamerlingh-Onnes and his laboratory accomplished to liquify helium whose boiling temperature is about 4.2 K under atmospheric pressure. Thus he could discover the superconductivity of mercury in 1911.
In the following years many other superconductors have been discovered, even high temperature superconductors (HTS). HTS has the advantage that liquid nitrogen (77 K) is sufficient.
Superconducting magnets often consist of niobium titanium (NbTi) that has a critical temperature of approximately 10 K.
The colder part of current leads is frequently built with HTS for very large currents.
The title refers to the double meaning of heavy. It is employed in physics as well as in music, only think of heavy metal. Thus a piece of tonal physics was created and performed at the barbecue of the Jazz & Pop School in 2018. When you listen to the recording, I recommend to close your eyes. Imagine you are chasing through the vacuum of the beam pipe with so many other ions of your bunch almost at the speed of light. Again and again you are accelerated by high frequency cavities, being kept on track by superconducting magnets. 🙂
As an example from the broad field of wavy falling films we take a simulation created with OpenFOAM. The picture displays a water falling film of a Reynolds number of 60 being harmonically excited with a frequency of 13 Hz. Gravitation points from the left to the right. The control volume is 600 units long (in the direction of the stream). One unit is the thickness of the corresponding smooth film. The height (perpendicular to the stream) is equal to 4 units being magnified by a factor of 50.
The red colour marks the water, the blue the air. Downstream a certain pattern can be recognized: A large solitary wave and in front of it small capillary waves.
The intuitive picture of a jet is a collimated spray of particles which is created by the collision of two particles in a high energy physics experiment. (There can be more than one jet.) Quantum chromodynamics (QCD) is the physical theory behind them. It states that a certain class of particles, hadrons, are built of quarks and gluons. If a quark or gluon is scattered, a jet is created. A quark or gluon has never been observed as a free elementary particle and QCD states that this is not possible. Instead after a scattering new particles are created very rapidly that can be observed. Regarded as a jet they have the momentum of the scattered quark or gluon. The exact definition of a jet is not trivial and there are sophisticated algorithms to find them.
Why are jets interesting to physicists?
With their aid conclusions can be made on the fundamental process without having to measure a free quark or gluon.