Astbury tried to determine the shapes of molecules of biological origin, by the technique of X-ray diffraction. X-rays have a similar nature to visible light rays, but have a much shorter wavelength; as X-ray wavelengths are comparable to the distances between atoms in molecules, rays scattered by different atoms ‘interfere’ with each other – if they are out of step, they cancel each other out and if they are in step, they reinforce each other. When a fine beam of X-rays falls on an object such as a hair, a photographic film shows a number of spots, which relate to regularities in the fibre, either along the length of the fibre or across its width, or a combination.