Mar 272014


Today is the birthday (1845) of Wilhelm Conrad Röntgen, a German physicist who produced and detected electromagnetic radiation in a wavelength range today known as X-rays or Röntgen rays, an achievement that earned him the first Nobel Prize in Physics in 1901. In honor of his accomplishments, in 2004 the International Union of Pure and Applied Chemistry (IUPAC) named element 111, roentgenium, a radioactive element with multiple unstable isotopes, after him.

Röntgen was born at Lennep in the Lower Rhine Province of Germany, as the only child of a merchant in, and manufacturer of, cloth. His mother was Charlotte Constanze Frowein of Amsterdam, a member of an old Lennep family which had settled in Amsterdam. When he was three years old, his family moved to Apeldoorn in The Netherlands, where he went to the Institute of Martinus Herman van Doorn, a boarding school. He did not show any special aptitude, but showed a love of nature and was fond of roaming in the open country and forests. He was especially apt at making mechanical contrivances, a characteristic which remained with him also in later life. In 1862 he entered a technical school at Utrecht, where he was however unfairly expelled, accused of having produced a caricature of one of the teachers, which was in fact done by someone else.

He then entered the University of Utrecht in 1865 to study physics. Not having attained the credentials required for a regular student, and hearing that he could enter the Polytechnic at Zurich by passing its entrance examination, he took the exam and began studies there as a student of mechanical engineering. He attended the lectures given by Rudolf Clausius and also worked in the laboratory of August Kundt. Both Kundt and Clausius exerted great influence on his development. In 1869 he graduated Ph.D. at the University of Zurich, was appointed assistant to Kundt and went with him to Würzburg in the same year, and three years later to Strasbourg. In 1874 he qualified as Lecturer at Strasbourg University and in 1875 he was appointed Professor in the Academy of Agriculture at Hohenheim in Württemberg. In 1876 he returned to Strasbourg as Professor of Physics, but three years later he accepted the invitation to the Chair of Physics in the University of Giessen.

After having declined invitations to similar positions in the Universities of Jena (1886) and Utrecht (1888), he accepted a post from the University of Würzburg (1888), where he succeeded Friedrich Kohlrausch and found among his colleagues Hermann von Helmholtz and Ludvig Lorenz. In 1899 he declined an offer to the Chair of Physics in the University of Leipzig, but in 1900 he accepted it in the University of Munich, by special request of the Bavarian government. Here he remained for the rest of his life, although he was offered, but declined, the Presidency of the Physikalisch-Technische Reichsanstalt at Berlin and the Chair of Physics of the Berlin Academy.

Röntgen’s first work was published in 1870, dealing with the specific heats of gases, followed a few years later by a paper on the thermal conductivity of crystals. Among other problems he studied were the electrical and other characteristics of quartz; the influence of pressure on the refractive indices of various fluids; the modification of the planes of polarized light by electromagnetic influences; the variations in the functions of the temperature and the compressibility of water and other fluids; the phenomena accompanying the spreading of oil drops on water.


Röntgen’s name, however, is chiefly associated with his discovery of the rays that he called X-rays. In 1895 he was studying the phenomena accompanying the passage of an electric current through a gas at extremely low pressure. Previous work in this field had already been carried out by numerous physicists, working on the properties of cathode rays – the name given to the electric current established in highly rarefied gases by the very high tension electricity generated by Heinrich Rühmkorff’s induction coil. Röntgen’s work on cathode rays led him, however, to the discovery of a new and different kind of ray.

On the evening of November 8, 1895, Röntgen found that, if the discharge tube is enclosed in a sealed, thick black carton to exclude all light, and if he worked in a dark room, a paper plate covered on one side with barium platinocyanide placed in the path of the rays became fluorescent even when it was as far as two meters from the discharge tube. During subsequent experiments he found that objects of different thicknesses placed in the path of the rays showed variable transparency to them when recorded on a photographic plate. When he immobilized his wife’s hand in the path of the rays over a photographic plate, he observed, after developing the plate, an image of her hand which showed the shadows thrown by the bones of her hand and that of a ring she was wearing, surrounded by the penumbra of the flesh, which was more permeable to the rays and therefore threw a fainter shadow. This was the first “röntgenogram” ever taken. Apparently when she saw her skeleton she exclaimed “I have seen my death!”


In further experiments, Röntgen showed that the new rays are produced by the impact of cathode rays on a material object. Because their nature was then unknown, he gave them the name X-rays. Later, Max von Laue and his pupils showed that they are of the same electromagnetic nature as light, but differ from it only in the higher frequency of their vibration.

At one point while he was investigating the ability of various materials to stop the rays, Röntgen brought a small piece of lead into position while a discharge was occurring. Röntgen thus saw the first radiographic image, his own flickering ghostly skeleton on the barium platinocyanide screen. He later reported that it was at this point that he determined to continue his experiments in secrecy, because he feared for his professional reputation if his observations were in error.

Röntgen’s original paper, “On A New Kind Of Rays” (Über eine neue Art von Strahlen), was published on 28 December 1895. On 5 January 1896, an Austrian newspaper reported Röntgen’s discovery of a new type of radiation. Röntgen was awarded an honorary Doctor of Medicine degree from the University of Würzburg after his discovery. He published a total of three papers on X-rays between 1895 and 1897. Today, Röntgen is considered the father of diagnostic radiology, the medical specialty which uses imaging to diagnose disease and other medical ailments.

Numerous honors were showered upon him. In several cities, streets were named after him.  He received numerous prizes, medals, honorary doctorates, honorary and corresponding memberships of learned societies in Germany as well as abroad and, of course, the Nobel Prize in physics of 1901 – the first time it was offered. In spite of all this, Röntgen remained a strikingly modest and reticent man. Throughout his life he retained his love of nature and outdoor occupations. He spent many vacations at his summer home at Weilheim, at the foot of the Bavarian Alps, where he entertained his friends and went on many expeditions in the mountains. He was a great mountaineer and more than once got into dangerous situations. Amiable and courteous by nature, he was always sympathetic to the views and difficulties of others. He was always reluctant to have an assistant, and preferred to work alone. Much of the apparatus he used he built himself with considerable ingenuity and experimental skill.

Röntgen was married to Anna Bertha Ludwig (m. 1872, d. 1919) and had one child, Josephine Bertha Ludwig. Adopted at age 6, in 1887, she was the daughter of Anna’s brother. Röntgen died on 10 February 1923 from carcinoma of the intestine. It is not believed his carcinoma was a result of his work with ionizing radiation because of the brief time he spent on those investigations, and because he was one of the few pioneers in the field who used protective lead shields routinely.


Röntgen did not take patents out on his discoveries, and donated the money for his Nobel prize to the University of Würzburg. With the inflation following World War I, Röntgen fell into bankruptcy later in life, spending his final years at his country home at Weilheim, near Munich. In keeping with his will, all his personal and scientific correspondence were destroyed upon his death.

Sauerbraten is a favorite dish throughout Germany and is served in many German restaurants worldwide.  It is a roast (usually of beef or venison) that has been marinated for 3 to 4 days in vinegar, wine, vegetables, and various spices. Marinating the meat acts as a tenderizer, resulting in tender, soft, juicy meat. There are several regional variations of the Sauerbraten, differing mainly by ingredients of the marinade. Rheinischer Sauerbraten, a specialty of Rhineland-Palatinate (Rheinland Pfalz) and North Rhine-Westphalia (Nordrhein-Westfalen) where Röntgen was born, is the most well known version. Unique to the Rheinischer Sauerbraten is that it is served with a a slightly sweet sauce made with raisins.

Historically, horse meat was used to make Sauerbraten. However, today beef or venison is most often used. As the name suggests, Sauerbraten has a slightly sour flavor. However, it is served with a complementing sauce that balances this out. In some variations, such as the Rheinischer Sauerbraten, the sauce has a slightly sweet flavor. Also, Sauerbraten should be very tender and soft. The marinade serves both as a flavoring agent and as a tenderizer. The longer the meat is able to marinade, the softer and more flavorful it will become.

Sauerbraten is traditionally served with potato dumplings (Klöße or Knödel), red cabbage, and apple sauce. If you don’t care for potato dumplings, Sauerbraten also goes very well with Spätzle, potato pancakes (Kartoffelpuffer or Reibekuchen), and boiled potatoes.


Rheinischer Sauerbraten   (Rhineland Sauerbraten)

1 cup red wine vinegar
1 ½ cups water
½ teaspoon black peppercorns
2 cloves
5 juniper berries
2 bay leaves
2 lb beef roast (boneless)
4-5 slices bacon, minced
2 onions, coarsely chopped
1 carrot, chopped
1 celery stick, chopped
4 tablespoons oil
freshly ground pepper
3-4 lebkuchen
½ cup red wine
¾ cup raisins
apple butter, apple juice, or red current jelly, to taste


Add water and red wine vinegar to a pot. Bring to a boil. Grind down peppercorns, cloves, and juniper berries slightly. Add this, as well as the bay leaves to the boiling liquid. Cook for 2 more minutes, then remove from heat and allow to cool.

Place the beef roast in a large Ziplok bag.. Pour the cooled red wine vinegar mixture over the beef,and zip up all but a small hole in the top.  Squeeze out all the air so that the meat is completely surrounded by marinade and then close the top completely. Refrigerate for 3 days.  If you are neurotic you can flip the bag once per day but it is not necessary.

To cook the meat, begin by heating oil in a roasting pot. Add the bacon and cook until most of the fat has been rendered.

Remove the beef from the marinade. Pat the meat dry with a cloth or some paper towels. Season the meat with salt and pepper. Place the meat in the roasting pot and sear each side. Add vegetables to the pot with the meat and allow them to cook with the meat.

Pour the marinade through a strainer into a pot. Heat the marinade to a boil.  Add about 1 cup of the hot marinade to the meat along with the Lebkuchen. Cover the pot, reduce the heat to low, and cook the meat for 2 hours. About half way through the cooking, add the red wine.

Once the meat is finished cooking, remove the meat from the pot. Cover and keep warm. Pour the liquid and vegetables from the pot through a strainer into a bowl or pot. Return the liquid to the original pot. Mix in raisins and allow the sauce to cook down, until it is thicker. Season with salt, pepper, and optionally the apple sauce or red current jelly.

Slice the sauerbraten and serve with the sauce.