On January 5, 1896, the Austrian newspaper Wiener Presse reported the discovery of a new kind of radiation. This new kind of radiation would come to be known as an X-ray, and its discoverer, by German physicist Wilhelm Roentgen, went on to win the Nobel Prize in 1901. X-rays are a part of the electromagnetic spectrum invisible to the human eye. (“Ray” is short for “radiation.”) Unlike radiation from the visible spectrum, X-rays can penetrate solid matter. This allows us to take pictures of the inside of objects.

X-rays can be both harmful and helpful. While exposure to large amounts of any form of radiation can be damaging to human health, small doses of X-rays can be used for a variety of useful purposes. Since Roentgen’s discovery, X-ray machines have transformed dentistry and medicine by allowing doctors to examine the inside of a patient’s body without surgery. X-ray machines are used to keep us safe at airports by examining the inside of sealed packages, and even our clothing. X-rays are also used in special observatories to help us explore the galaxy by detecting the radiation given off by planets, moons, and other objects in space.

electromagnetic spectrum

continous band of all kinds of radiation (heat and light).


collection of stars, planets, gases, and other celestial bodies bound together by gravity.


natural satellite of a planet.

Nobel Prize

one of five awards established by the Swedish businessman Alfred Nobel in 1901. Nobel Prizes are awarded in physics, chemistry, medicine, literature, and peace.


to push through.


person who studies the relationship between matter, energy, motion, and force.


large, spherical celestial body that regularly rotates around a star.


energy, emitted as waves or particles, radiating outward from a source.

visible light spectrum

light and colors that can be seen by human beings.


radiation in the electromagnetic spectrum with a very short wavelength and very high energy.