1.   To solve the mystery, Spiropulu and other physicists send particles smashing into each other at very high speeds, and examine the spray of wreckage.

2.   When turbulence in the air sends particles crashing into one another, electrons get ripped loose and those particles usually end up with either a positive or negative charge.

3.   The hastily built sarcophagus is leaky, and Ukrainian and Western officials say parts of it could fall on the nuclear fuel and send particles into the atmosphere.

4.   They mistakenly put in too much uranium, setting off an uncontrolled atomic reaction that continued for hours, sending radioactive particles into the air.