X-ray of Lord Kelvin's hand An X-ray of Lord Kelvin’s hand (1896). © Royal Society.

By Royal Society Wolfson Research Merit Award holder Professor Matt Zepf

What are X-rays?

Everyone is familiar with the most common use of X-rays – to take pictures of our (broken) bones without the need for surgery. But what are X-rays? Essentially, they are the same phenomenon as the light that we can see, but with a much smaller wavelength. The change in wavelength alters the properties of the wave quite significantly – the shorter the wavelength the more penetrating X-rays become. This allows the safety personnel in Heathrow to peer deep into your suitcases and humanity to peer deep into nature’s secrets.

How have X-rays changed the way we see the world?

Other than taking pictures through thick, opaque objects like our bodies, their small wavelength also means that they are sensitive to tiny objects like atoms. Consequently X-rays can tell us about the structure of the world - without X-rays we would not know that our genes are arranged in the spiral-staircase like form of the double-helix.

Is X-ray technology still improving?

Scientists constantly strive to make better and brighter X-ray sources, as they are exceptional tools for understanding the world around us. The latest X-ray sources are being developed to have pulse durations of a mere millionth of a billionth of a second - that is about the same length of time that it takes an electron to orbit an atom.

What will we use them for in future?

Such short pulses of X-rays will allow us to see not only where electrons are located but will also lead to movies of atoms and molecules in action.