Dig deeper at pwnphysics.blogspot.comOn this day in physics: 15 January 2005 the SMART-1 Moon Orbiter confirms that there is indeed calcium present on the moon.Word of the Day: Mho. Electrons travel at very fast speeds (close to the speed of light!) in all the wires that power everything from your phone, computer, television, refrigerator, stove, car, et cetera. Very specific metals are chosen because they allow the electrons to flow freely, and without any interference, sort of like friction. This friction generates a lot of heat, and slows down the electrons, also reducing the current. Sometimes this effect is desired, so engineers will add what is known as a resistor, to give a desired current, or to actually generate heat. The unit Ohm describes the measure of difficulty with which electrons pass a current through a conductor. The inverse, or opposite of resistance is called conductance. It is the measure of ease with which electrons pass through a conductor. Thus items with high conductances are called good "conductors". And now the light side and bad jokes that physicists have come out. Since the measure of resistance is known as the Ohm, the opposite is Ohm spelled backwards, or the Mho. It is also known as the Siemens, which is equal to exactly the reciprocal of one Ohm.