function didYouKnow() {

nmsg = 18;
arraymsg = new Array(nmsg);

arraymsg[0] = "The Moon does not orbit around the center of the Earth. Instead, the Moon and Earth actually both orbit around their common center of gravity, which is located 1600 kilometers beneath the surface of the Earth and is on a straight line between the centers of the Earth and Moon. The center of the Earth makes a small circle around that center of gravity every 27.33 days.";

arraymsg[1] = "A 'light year' is a measure of distance, not time. It is the distance that light travels in a year and is equal to about 9.5 trillion kilometers, or about 6 trillion miles.";

arraymsg[2] = "An atomic clock kept at the National Bureau of Standards in Boulder, Colorado, U.S.A., 1650 meters above sea level, gains about five microseconds each year relative to an identical clock kept at the Royal Greenwich Observatory, 25 metres above sea level. The reason is that gravity gets stronger as one gets closer to the Earth's core, and, according to Einstein's Theory of Relativity, time passes more slowly in stronger gravitational fields.";

arraymsg[3] = "A perpetual motion machine would violate the laws of thermodynamics. No one has ever built one, and no one ever will.";

arraymsg[4] = "Light can exert a force. The force of the Sun's light on Earth's surface has been determined to be two pounds per square mile.";

// arraymsg[5] = "The sky is blue because of refraction. The Sun's light is of all colors of the rainbow, mixed together to make white light. The reds and yellows pass through air easily, but some of the blue portion of sunlight is scattered in every direction by air molecules. This scattering causes the sky to be blue.";

// arraymsg[6] = "The air around us is not weightless. In fact, it can be weighed almost as accurately as iron or lead. A column of air 1 inch square and 600 miles high, for instance, weighs approximately 15 pounds, about twice as much as an average newborn baby. This weight is what creates the phenomenon known as 'atmospheric pressure.'";

arraymsg[5] = "Ten of the 105 known elements had been discovered and were in use in prehistoric times: gold, silver, lead, iron, copper, zinc, tin, sulfur, carbon, and mercury. The largest individual contribution to the Periodic Table of Elements was that of the nineteenth century English chemist Sir Humphrey Davy, who identified boron, barium, calcium, potassium, sodium, and strontium in 1807 and 1808. He also demonstrated that diamonds are composed of pure carbon and discovered the hilarious properties of nitrous oxide --'laughing gas.'";

arraymsg[6] = "If the chemical sodium is dropped in water and a match is taken to the mixture, it will immediately and violently ignite. If sodium is immersed in a pot of kerosene, however, it will not burn at all.";

arraymsg[7] = "Sound travels fifteen times more swiftly through steel than through air.";

arraymsg[8] = "According to Albert Einstein's Theory of Relativity, the mass of an object increases with its speed. In nonscientific terms, this means that things get heavier as they move faster. The process has been demonstrated in laboratories. In several experiments, objects accelerated to 86 percent of the speed of light have doubled in mass.";

arraymsg[9] = "A pipe 2 feet (61 cm) in diameter will allow four times more fluid to pass through it than a pipe 1 foot (30.5 cm) in diameter-the volume of a pipe varies as the square of its diameter.";

// arraymsg[12] = "If you punch a series of holes in a paper cup filled with water, the water will squirt out farthest and fastest from the lowest holes. The reason is that water pressure is greatest at the bottom of the cup. For the same reason, dams are made thicker at the bottom than at the top.";

arraymsg[10] = "As objects approach the speed of light, from the viewpoint of someone standing still they get shorter, their color begins to change, and time around them even slows down!";

arraymsg[11] = "Physicists have developed a way to 'trap' atoms. By using magnetic fields and polarized laser light, they are now able to slow down atoms to the point that they are at almost 1 millionth of a degree from absolute zero!";

arraymsg[12] = "We only see our 3 basic dimensions (height, width, and length). However, in our world there are at least 4 dimensions, because time is ALSO a dimension. In addition, some scientists believe that there may be another 6 or 7 dimensions that we can't see!";

arraymsg[13] = "There are more planets than the eight we know about in our Solar System. Scientists have discovered more than 200 planets around other stars in our galaxy, and they probably will discover hundreds more in the near future!";

arraymsg[14] = "A black hole has a gravitational pull that is so strong, it can even pull in light (which is why the hole is black!).";

arraymsg[15] = "Light from modern synchrotrons can be a billion times more intense than light from the Sun!";

arraymsg[16] = "Sound waves can be used to 'see' inside all sorts of materials, like the spot welds in the cars you drive not just pregnant mothers!";

arraymsg[17] = "When a fast-moving plane pushes through the air waves that form in front of it (a shockwave), it creates a sonic boom. The sonic boom sounds when the plane is going faster than 760 mph (about 1220 km/h)."



ranint = Math.floor(Math.random()*nmsg);
dyknowmsg=arraymsg[ranint];
//  document.write("<p>integer = "+ranint+"</p>");
document.write(dyknowmsg);

}