Archive for October, 2015

The Heidelberg “Schlossbeleuchtung” and the age of spectroscopy

October 23, 2015

If you walk down the famous Hauptstraße (Main Street) in the old town of Heidelberg you may notice a memorial plate on the facade of the “Haus zum Riesen” (No. 52) which tells you that Gustav Kirchhoff and Robert Bunsen laid here the foundations of modern spectroscopy. Besides the new opportunity to detect elements in small quantities and the discovery of two new elements (caesium and rubidium) from salt of Dürkheim mineral water), a pioneering major breakthrough of this marvellous collaboration of a physicist and a chemist was the application of spectral analysis to celestial bodies – opening the field of cosmic chemistry.

Less well known is the background of their idea. In a 1912 article, Heidelberg astronomer Max Wolf mentions in a footnote an oral tradition by Henry Enfield Roscoe via Bohuslav Brauner (a student of Bunsen and Roscoe): On the occasion of a visit of the Grand Duke of Baden in Heidelberg (probably on 1 June 1860), the Heidelberg Castle was illuminated (“Schlossbeleuchtung”) at night with Bengal fire. Bunsen pointed from the roof of his laboratory a prism set against these flames and observed clearly the green lines of barium and the red lines of strontium. He said to Kirchhoff: “If we could see at that distance, which substances were glowing in these flames – why could we not also determine out of which substances the celestial bodies consist?” – Thus, the spectral analysis of the sun and the stars was born.

Footnote from Max Wolf's article "Der Einfluss kosmischer Probleme auf die Entwicklung der Spektralanalyse", Zeitschrift für Elektrochemie und angewandte physikalische Chemie 18, p. 457 (1912).

Footnote from Max Wolf’s article “Der Einfluss kosmischer Probleme auf die Entwicklung der Spektralanalyse”, Zeitschrift für Elektrochemie und angewandte physikalische Chemie 18, p. 457 (1912).

At a workshop at MPIK for this year’s International Summer Science School Heidelberg students, I prepared an experiment demonstrating this historic discovery. The students were looking at the flames of red and green Bengal fire through a simple hand spectroscope and could identify the spectra of strontium and barium.

Hand spectrometer used for the workshop.

Hand spectrometer used for the workshop.

Spectra of Sr and Ba in red and green Bengal fire flames.

Spectra of Sr and Ba in red and green Bengal fire flames.


A Neutrino Matchbox

October 6, 2015


This box contains about …

8,300 Cosmic background neutrinos of each species, i.e. 50,000

320 Solar neutrinos

7.5·P/D2 Reactor neutrinos (P: thermal power in GW, D: distance in km)

Traces of supernova & atmospheric neutrinos, geoneutrinos

The front side of the box mantle tells you how many neutrinos (of different kind and from different sources) are contained in the box (148 cm3 volume). The back ‘Dark Side’ the composition of the total energy of the universe in form of a pie chart.

The proportions of the three edges of the box follow the golden ratio and the absolute value of the middle-size edge length is 5.29 cm, i. e. 1 Billion times the Bohr radius.

Inside is an (updated) excerpt from John Updike’s poem ‘Cosmic Gall’ (original version published in The New Yorker on Dec. 17, 1960) on top of the first bubble chamber picture of a neutrino event (Nov. 13, 1970).

One of the face sides illustrates geometrically two (phenomenological) relations of the neutrino mixing angle ϑ12 to the golden ratio (see also

The papercraft sheets (PDF) of the Neutrino Matchbox can be downloaded here: (English version, German version).