Do radioactive things glow?
In general, no. The green ooze stereotype is a fabrication of comics. Most radioation is impossible to detect without special equipment. However, when extremely radioactive material is placed underwater (such as in a nuclear reactor), it makes a blue glow. This is called Cherenkov radiation. It is an optical shockwave, like a sonic-boom, that occurs when charged particles (alpha particles, beta particles, fission products) are emitted faster than the speed of light in a medium. Since light travels through water slower than it does in a vacuum, this does not violate relativity.
