Tensile Strength, the ability of a material to withstand a pulling (tensile) force. It is customarily measured in units of force per cross-sectional area. For example, if a metal rod one square inch in cross section can withstand a pulling force of 1,000 pounds but breaks if more force is applied, the metal has a tensile strength of 1,000 pounds per square inch.
An invisibility cloak seems perfectly believable in the magical world of Harry Potter, but in the real world, it's impossible, right? Not so fast.
British authorities have found traces of polonium-210 in at least five buildings and three British Airways jets since Alexander Litvinenko fell ill.