"Whether scientific discoveries are regular or not" is a philosophical question, but there is no doubt that the mysteries of the universe and nature and the characteristics of all matter need to be determined by quantitative systematic experiments and measurements.
Written by | Zhizhong Lin (Department of Electronic Physics, Taiwan Jiaotong University)
Source | This article is from Physics, No. 12, 2021
X-rays (X-rays) were accidentally discovered on November 8, 1895 by the German physicist Wilhelm C. R ntgen (1845-1923), which earned him the first Nobel Prize in physics in history in 1901 – the Swedish chemist Nobel happened to make a will more than half a month before the X-ray was discovered, donating a legacy to establish the Nobel Prize. However, Roentgen refused to patent X-rays, declined suggestions from colleagues and friends to name them after themselves (although later generations still refer to X-rays as Roentgen rays), and declined to address the Nobel Prize. In his will, Röntgen donated his Nobel Prize to the University of Würzburg as a research grant, but unfortunately due to the severe inflation after the First World War, the prize he donated later became almost nothing like waste paper. As soon as the X-ray was discovered, the medical community at that time immediately recognized its unlimited medical value and immediately applied it to hospitals. In 1900, the German army was equipped with mobile X-ray machines to medically treat wounded soldiers on the battlefield.
1
X-rays were discovered
In the second half of the 19th century, due to the dual development of electrical engineering and scientific research after the Industrial Revolution and the urgent social needs, the study of "cathode rays" and "gas discharge" (in vacuum tubes) became an apparent science, involving countless scientists, including young physicists such as Heinrich Hertz, Philipp Lenard and J. J. Thomson in Europe, as well as inventor Tesla ( Nikola Tesla) 。 Before the discovery of X-rays, Röntgen had not done any experiments related to cathode rays, in other words, he was a novice in the field of cathode rays and gas discharges. Moreover, a year before the X-ray experiment, he was elected by the chancellor professor to be the rector of the University of Würzburg for a year because of his outstanding academic reputation. In October 1895, after he stepped down as headmaster, he began experimenting with cathode rays. So, why was it Röntgen and not his contemporaries, who were the first to discover X-rays, rather than other experienced and skilled competitors of his generation? In particular, one thing is fairly certain that at the time of Röntgen's experiments, and even a few years before, in several cathode ray laboratories everywhere, X-rays must have been repeated and seen. However, because they have prejudices in their hearts and do not know why they are so, they "turn a blind eye" and carelessly lose Jingzhou, which is lost with precious scientific discoveries and honors throughout the ages.
Why did Röntgen discover X-rays? There is a reasonable explanation as follows: Röntgen is an excellent experimental physicist, he is handy in the mastery and use of the instrument, in the measurement process to observe the nuances, but also able to rigorously verify and demonstrate the measurement data. Majoring in mechanical engineering in college, Röntgen specialized in the thermal conductivity of gases and the principles and construction of steam engines (his thermodynamics course was taught by Rudolf Clausius, the "father of thermodynamics"), so he liked to design and assemble (simple) experimental instruments himself and make his own measurements (Fig. 1). This research orientation and habit, on the one hand, was due to the European academic atmosphere at that time, which allowed Roentgen to have the advantage of benevolence and beauty, and to take the law; on the other hand, because Roentgen's personality traits were indeed different from his peers, he had a strong sense of precise experimentation and preference, and rarely asked assistants to help measure. Moreover, Röntgen attached great importance to the experimental tradition in the rise and development of modern science in Europe, and he highly affirmed the key and critical role played by experiments and observations and objective logical reasoning (the scientific method) since the 16th century.
Figure 1 The laboratory where Röntgen discovered X-rays at the University of Würzburg, photo from the "German R entgen Museum"
When Röntgen became chancellor of the University of Würzburg in January 1894, he went against the academic tradition of the time and did not present his main research at the inauguration ceremony, but gave what he thought was the development of modern science (in Europe). In it, he emphasizes that since the 16th century, the community of natural scientists "has gradually developed the belief that cognitive experiments are the most powerful and reliable means of exploring (torturing) the mysteries of nature, and that experiments represent the supreme authority for determining whether a hypothesis should be retained or discarded." Röntgen affirms that scientific experiments are those that are carefully designed, rigorously executed, and whose interpretation of phenomena is based on measurement data (objective evidence). Later historians of science believe that Röntgen was a very rigorous, meticulous, observant, and clear-thinking experimental physicist.
On the evening of Friday, November 8, 1895 (Röntgen likes to experiment on weekend nights because he could concentrate his mind without interference from colleagues or students), Röntgen first spotted a bright light on a fluorescent screen about 1 m outside the cathode ray tube (a distance that cathode rays could not reach). He soon realized that this bright light was not a point of light caused by any known physical phenomenon or ray (or particle flow). He then switched the power supply of the cathode ray tube several times, so as to clearly determine that the appearance or disappearance of this fluorescence was instantaneous, from the opening or closing of the cathode ray tube. At this point, he ruled out the suspicion that the light was phosphorescence, because the light and shade of phosphorescence changed gradually, requiring a little buffer reaction time.
After guessing that X-rays were highly penetrating new rays (or streams of particles), Röntgen immediately took a series of steps, working to make various measurements, trying to synthesize and generalize the physical properties of their 1). This is a crucial step in establishing and consolidating Röntgen's X-ray discoverer status, because facts speak louder than words, and letting comprehensive experimental evidence speak is the only way to judge the truth or falsity of the natural sciences. Over the next 6 weeks, Röntgen experimented, asking himself repeatedly, trying to answer the following questions, including whether the X-rays were straight forward? Do they reflect or refract? Are they different from cathode rays? What exactly are they? Röntgen quickly verified that the paths of X-rays were not affected by magnetic fields, so they were not cathode rays. Röntgen also confirmed the strong penetration of X-rays and the ability to image light on photographic negatives in addition to producing fluorescence. Because of the ability to image on negatives and see for themselves, the X-ray discovery caused a stir between scientists on both sides of the Atlantic and the public and the media as soon as they were announced. In addition, as we all know, Röntgen was even more surprised to find that in addition to penetrating paper, books, wood, and thin sheets of metal, X-rays were also able to penetrate human skin.
Although he was sure that he had discovered a new ray (or particle stream), Röntgen was very anxious, and he was afraid that the light on these screens was only a hallucination (valerian) caused by the fatigue of the eyes due to working in the dark room for a long time. He feared that if he had rashly published unreal and illusory measurements, he would have lost his reputation and his academic career would have come to an end. So in the process of repeated self-questioning and testing, he was in a trance, did not talk to people, and forbade anyone to enter the laboratory. It wasn't until December 22 that Röntgen finally invited his wife to the lab and asked her to allow him to take X-rays of her hands, which is the origin of the X-ray photographs of Mrs. Roentgen's fingers and wedding rings in the history of science. (Before filming her wife's hand, Röntgen had inadvertently discovered that X-rays would penetrate his own skin, but he was reluctant to tell anyone and was still a little worried that it was an illusion caused by eye fatigue.) When, unprepared, she suddenly saw a picture of her own hand bones, Madame Roentgen seemed to be overly frightened and refused to enter the laboratory again. Röntgen decided to immediately make the results of his experiment public, saying to his wife, "Now the devil will be topay." )
2
Published quickly, in a single volume
After establishing the penetrating nature of X-rays and taking hand images, Röntgen quickly wrote about his astonishing discovery, titled the paper "On a New Kind of Rays: A Preliminary Communication." Moreover, Röntgen did not submit the paper to the prestigious national physics journals of the time, such as Annalen der Physik, which were highly regarded academically, but submitted them to the local Proceedings of the Würzburg Physical Medical Society for publication on December 28 (during the Christmas holiday), and urged them to make an exception for the same day. At this time, Röntgen turned 50 years old, and although he was only a novice in the field of cathode rays, he was no longer a generalist in academia, or a multitude of sentient beings. Obviously, Röntgen is well aware of the irreplaceable metrics and absolute significance of prioritizing publication in the history of science. Presumably, after much deliberation and inner torment, he wisely chose a local (local) journal to successfully complete the publication task, thus taking on the title of "X-ray Discoverer" that could not be rewritten.
On 23 January 1896, Röntgen read his thesis at a regular meeting of the Würzburg Physical Medical Society, the first and last official lecture on X-rays in his life. Then, in 1896 and 1897, he also published an X-ray paper at the Proceedings of the Würzburg Physical Medical Society. These three papers and the only public lecture were like his "solitary papers"2), and Röntgen has not left a single word on X-rays since then. In 1900, Röntgen left the University of Würzburg and became director of the "Institute of Experimental Physics" at the University of Munich, where he regained his early interests and focused again on the study of the physical properties of crystals.
Figure 2 X-ray photograph of the hand of the famous anatomist Kolik taken by Roentgen at the scene of his speech, taken from the X-ray | Psychology Wiki| Fandom (wikia.org)
At a meeting of the Würzburg Physical Medical Society, Röntgen photographed his hand on the spot for Albert von K lliker, the famous anatomist of the time, who was present at the lecture, and this radiograph was still clear and thorough even by today's standards more than 100 years later (Figure 2). It was also in this talk that K lliker suggested naming X-rays "Roentgen rays."
3
Promote the establishment of the "Institute of Theoretical Physics" at the University of Munich
In my opinion, Röntgen's two major scientific contributions were the discovery of X-rays (a contribution known to the general public) and the painstaking effort to establish the "Institute of Theoretical Physics" at the University of Munich in the mid-1900s (a contribution that may be little known). For a brief period of four years, from 1890 to 1894, Ludwig Boltzmann was Chair Professor of Theoretical Physics at the University of Munich, but after Boltzmann's departure, the position of Professor of Theoretical Physics at the University of Munich was vacant for many years until the "Institute of Theoretical Physics" was founded and Arnold Sommerfeld was recruited as its first director. Due to the arrival of Sommerfeld (1906), a few years later the "Munich School" formed a brilliant situation in which the three peaks of the "Göttingen School" and the "Copenhagen School" stood side by side, and wrote a brilliant and colorful heroic deed for the development of quantum mechanics 20 years later. Roentgen strives to set up the "Institute of Theoretical Physics" at the University of Munich in addition to the "Institute of Experimental Physics", so that the theory and experiment can interact with each other and cooperate closely with each other, which is another major contribution to the development of modern physics, which deserves the admiration and nostalgia of future generations.
footnote
1) X-rays are often written in English as the plural X rays, so "they" Chinese used here.
2) Among the Quan Tang poems, Zhang Ruoxuan only has two remaining poems, and his "Spring River Flower Moon Night" is known as "a lone piece pressing the whole Tang".
postscript
In his will, Roentgen demanded the destruction of all his personal and scientific correspondence— correspondence— and what he called for in his heart (after the discovery of X-rays) seemed to be a profound and obscure scholarly life, as (Tang) Lu Zhaolin wrote in his poem "Chang'an Guyi": "Lonely and few Yangziju, years and a bed." Unique Nanshan osmanthus hair, flying around to attack people. ”
This article is reprinted with permission from the WeChat public account "Chinese Physical Society Journal Network".
Special mention
1. Enter the "Boutique Column" at the bottom menu of the "Return to Simplicity" WeChat public account to view the series of popular science articles on different topics.
2. "Return to Park" provides the function of retrieving articles on a monthly basis. Follow the official account, reply to the four-digit year + month, such as "1903", you can get the index of articles in March 2019, and so on.