Aerodynamics, the branch of physics that deals with the motion of air and with the relative motion between air and objects in the air. The bodies in the air can be moving (for example, aircraft, missiles, birds, and automobiles), or they can be stationary structures (for example, bridges and buildings) acted upon by moving air. Aerodynamicists are concerned mainly with the design of airplanes and, to a lesser extent, automobiles. The flight of birds demonstrates many of the principles of aerodynamics.
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.