Wilhelm Röntgen publishes a paper detailing his discovery of a new type of radiation, which later will be known as x-rays.

Wilhelm Conrad Röntgen, sometimes transliterated as Roentgen, was a German physicist who produced and detected electromagnetic radiation in a wavelength range known as X-rays. As a result of this discovery, he became the first recipient of the Nobel Prize in Physics in 1901.

In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes:

• electromagnetic radiation consisting of photons, such as radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma radiation (γ)
• particle radiation consisting of particles of non-zero rest energy, such as alpha radiation (α), beta radiation (β), proton radiation and neutron radiation
• acoustic radiation, such as ultrasound, sound, and seismic waves, all dependent on a physical transmission medium
• gravitational radiation, in the form of gravitational waves, ripples in spacetime

An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ranging from 10 nanometers to 10 picometers, corresponding to frequencies in the range of 30 petahertz to 30 exahertz (3×10¹⁶ Hz to 3×10¹⁹ Hz) and photon energies in the range of 100 eV to 100 keV, respectively.