<human>:  When a gamma ray hits a nucleus, what happens?
<bot>: The gamma ray will cause the nucleus to emit a particle of light, which is called a photon. The photon has the same mass as the gamma ray, and it has the same energy. However, the photon is traveling at the speed of light, which is a very fast speed. The gamma ray is slowed down as it travels through the nucleus, and the nucleus is destroyed.