Since every isotope that spews gamma or X rays or charged particles does so in a unique way--an atomic fingerprint, of sorts--the color and intensity of the flash tells the detector which isotope is present and in what quantity.

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Meanwhile, the newly real particles decay, giving off (among other things) light, X-rays and gamma rays.

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As the particles turn around the circle, they lose energy in the form of exceptionally intense X-rays.

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X-rays, and observing how the rays are scattered, the researchers have concluded that the balls are full of particles with a diameter of about 50 billionths of a metre.

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