"Time will tell. We have a beginning now; developments will come with time."
— Wilhelm Conrad Röntgen, The New Marvel in Photography (1896)
The first experiments with electrical discharges in a vacuum (or near vacuum) were conducted by the German Heinrich Geissler (1814–1879), a specialist in vacuum technology and glasswork. This study caught the attention of the British physicist Michael Faraday, who sought to study the relationship between electrical conduction in a gas and the pressure inside the tube. Faraday observed a faint light produced by the electrical discharge in the gas and noted the existence of a dark section in the tube, today called the Faraday Dark Space.
Faraday also observed variations in the emitted spectrum (colors) depending on the type of gas used and the nature of the electrode. This would later become crucial in spectrometry, which allows materials to be characterized based on the light they emit.
 |
| Faraday dark space in the middle. |
Subsequent studies by the German physicist Heinrich Geissler (1814–1879) led to the construction of tubes containing residual gas inside, equipped with platinum wire electrodes (anode and cathode). When a positive voltage was applied between the anode and cathode (cold cathode), these tubes generated light from the ionized gas. Geissler varied the voltage levels between the electrodes and observed the effects on the emitted light.
Julius Plücker, who worked alongside Geissler and Jonathan Hittorf, demonstrated that at very high voltages and with cold cathodes, the gas would ionize, but it was also possible to observe a beam of particles moving in a straight line.
In 1876, Eugen Goldstein (1850–1930) named these strange particle beams Cathode Rays. Goldstein identified that the rays were emitted perpendicularly from a metallic surface and that they carried energy.
In 1890, Arthur Schuster (1851–1934) demonstrated that cathode rays could be deflected by an electric field, while William Crookes (1832–1919) showed that they could also be deflected by a magnetic field. Crookes focused his studies on the behavior of the resulting spectra.
 |
| Cathode ray being deflected by a magnetic field as stated by Crookes. |
Building on Crookes' research, Heinrich Rudolf Hertz and Philipp Eduard Anton von Lenard, who was Hertz's assistant, made significant advancements in the study of cathode rays at the time.
Thanks to these researchers, and many others, scientific knowledge eventually led to the Crookes tube, which played a crucial role in the work of the German physicist Wilhelm Conrad Röntgen twenty years later.
In 1895, Röntgen began working with the Crookes tube in his small laboratory located at what is now the University of Applied Sciences in Würzburg. As said before, these tubes were carefully evacuated glass containers with two small metal plates placed at opposite ends. The plates were connected to the poles of a high-voltage generator, and when the current was passed through, a luminous radiation was emitted inside the tube—a type of luminescence that seemed to emanate from the remaining rarefied air within the tube. These experiments were conducted in dark laboratories to allow better observation of the faint radiations produced.
One day, while conducting an experiment, Röntgen covered one of these tubes with black cardboard. By chance, there was a screen coated with barium platinocyanide on a nearby table. With each discharge in the tube, the screen glowed with a greenish light. The phenomenon occurred whether the coated side of the screen faced the tube or not.
Röntgen concluded that the screen was being struck by an invisible radiation capable of passing through the black cardboard. This had to be a different kind of radiation, as the cardboard was opaque even to ultraviolet radiation.
For the following weeks, Röntgen dedicated himself entirely to identifying the properties of this newly discovered radiation. Since he was unsure of its nature, he named it X-rays. Soon after, Kölliker, a professor in Würzburg, proposed the name Röntgen Rays.
The experiments intensified. It became evident that this strange radiation originated from the high-vacuum tube. Röntgen then decided to place a book between the screen and the radiation source. To his surprise, the object cast only a faint shadow, indicating that X-rays could penetrate it.
Next, he placed his own hand in the path of the radiation. His hand also appeared transparent—except for the bones, which stood out in the shadow. Finally, he used a photographic plate, which captured an image of his fingers, revealing a transparency unlike any seen with ordinary light.
On December 22, 1895, Röntgen obtained the first X-ray image in history—a radiograph of his wife's hand.
 |
| X-ray of Röntgen's wife. |
The photograph confirmed that this was indeed a new form of radiation with the ability to penetrate opaque materials, only being blocked by substances with high atomic mass (such as lead and platinum).
Nowadays, given the spread of medical technology and varying levels of healthcare across countries, it is likely that hundreds of thousands of X-rays are conducted worldwide each day. In some estimates, the global number might exceed 1 million X-ray exams per day.
There are many stories analogous to the one above—a groundbreaking discovery like X-rays made possible by a long lineage of scientific "farmers" who cultivated the field of knowledge, each leaving behind fruits for the next to harvest—though perhaps only the most visible ones to the cultivator.
As stated by Isaac Newton in one of his letters to Robert Hooke:
"If I've seen further it is by standing on the shoulders of Giants."
Basic sciences explore and push the boundaries of scientific knowledge. By their very nature, they seek to bring new understanding to natural phenomena, mathematics, and the humanities, deepening our comprehension of the world. They also lead to discoveries that offer new opportunities and methods for studying nature and society, as well as enabling practical applications of scientific breakthroughs. All of this, in turn, contributes to educational, cultural, and intellectual enrichment and provides the scientific foundation for human development.
No comments:
Post a Comment