The circle in the middle of the trefoil represents an atom and the blades represent the three common types of ionizing radiation emanating from it — alpha (α), beta (β) and gamma (γ). The symbol was ...

Last updated at 17:50 15 February 2007 The UN nuclear watchdog has introduced a new radiation warning symbol showing emanating waves, a skull and crossbones, and a running person.

Most radioactive sources are used and contained inside a larger piece of equipment, protected by heavy shielding. The black, magenta or yellow trefoil symbol or the words “radiation” or “radioactive” ...

Directly looking for ionizing radiation from the first galaxies is out of the question. Intervening gas clouds absorb that faint light long before it reaches Earth.