When high sped trains past each other they must slow down or they will break their windows. The passing trains produce a low-pressure area between them that can actually pull the glass out of the frames.

Two celestial objects, of equal mass, sharing a single gravitional field, will exhibit  identical rotational properties, as long as their inertial integrity is maintained.

If hot water is suddenly poured into a glass that glass is more apt to break if it is thick than if it is thin. This is why test tubes are made of thin glass.

The Titanic was so enormous that its rudder alone actually outweighed Christopher Columbus' vessel, the Santa Maria. The Titanic was also longer than any New York City skyscraper at the time was tall. Who could have guessed it would have been safer in the midst of New York City traffic than plying the liner route across the North Atlantic? (Source: DO FISH DRINK WATER?)

WHAT DOES E=mc2 STAND FOR?
In 1905, the deep connection Albert Einstein discovered between energy and mass is expressed in the equation E=mc².   Here E represents energy, m represents mass, and c² is a very large number, the square of the velocity of light. This equation became a cornerstone in the development of nuclear energy.

What makes a boat float?
A boat floats, because the fluid in which it is floating offsets the downward pull of gravity and pushes it up. The scientific name for this force, which allows even immense objects to float in liquid, is buoyant force, more commonly known as buoyancy.

A solid object's density determines whether or not the buoyant force of a liquid can lift it. The density of an object depends upon its weight and its size. Given two solid objects that are different sizes, but weigh the same, the smaller, more compact object is the denser of the two.

Fluids also have density. When an object is placed in the fluid, it pushes aside some of the liquid and, if its density is greater than that of the fluid it displaces, it will sink and, if not, it will float.

Despite the enormous size of some ships, they are basically metal shells filled with air, and are less dense and lighter than the water they push aside, which allows the boats to float.

Copyright © 1994-2004 Yahoo! Inc. All rights reserved.

The Big Bang Theory
The Big Bang Theory is the dominant scientific theory about the origin of the universe. According to the big bang, the universe was created sometime between 10 billion and 20 billion years ago from a cosmic explosion that hurled matter and in all directions.  In 1927, the Belgian priest Georges Lemaître was the first to propose that the universe began with the explosion of a primeval atom. His proposal came after observing the red shift in distant nebulas by astronomers to a model of the universe based on relativity. Years later, Edwin Hubble found experimental evidence to help justify Lemaître's theory. He found that distant galaxies in every direction are going away from us with speeds proportional to their distance.  The big bang was initially suggested because it explains why distant galaxies are traveling away from us at great speeds. The theory also predicts the existence of cosmic background radiation (the glow left over from the explosion itself). The Big Bang Theory received its strongest confirmation when this radiation was discovered in 1964 by Arno Penzias and Robert Wilson, who later won the Nobel Prize for this discovery. Although the Big Bang Theory is widely accepted, it probably will never be proved; consequentially, leaving a number of tough, unanswered questions.

THE BIG BANG MAY HAVE BEEN COLLIDING UNIVERSES
A new theory about the "big bang" suggests that a collision with another universe helped create our cosmos. This theory from physicist Paul Steinhardt of Princeton University in New Jersey and colleagues is named "ekpyrosis," after the fire ancient Greek philosophers believed the universe emerged from. The ekpyrotic model conjectures that a cosmic impact sowed our previously cold and featureless universe with seeds of matter that would later grow into the galaxy we live in and the others we see in the sky. While this model does not necessarily explain where the colliding "Johnny Appleseed" universe came from, it may help explain several astronomical puzzles that currently plague scientists. Perhaps most importantly, it would help explain creation without resorting to "inflation," a hypothetical era in our universe's early history when it would have expanded at speeds faster than light-a phenomenon scientists since Einstein generally have believed impossible. The physicists say their ekpyrotic model would also help explain why far-flung parts of the sky seem to unreasonably have roughly the same temperature and why our universe apparently has no overall curvature. They contend the new idea can be tested in experiments because it makes measurable predictions concerning gravitational waves and unevenness in the low-energy microwave radiation that pervades our universe. The scientists presented their findings at the Space Telescope Science Institute in Baltimore, Md.

THE MUSIC OF CREATION
Scientists have detected the sound of creation, The Australian reports. They have picked up echoes of the big bang, the explosion thought to have signaled the birth of the universe 12 billion to 14 billion years ago. The echoes are the remnants of huge acoustic waves that surged through the matter generated in the big bang. Some physicists have suggested that such waves shaped the modern universe by concentrating matter in some areas and removing it from others. Until now there had been no real evidence. The research was undertaken by an international team of scientists who surveyed the sky over Antarctica. They used a 1600kg telescope suspended from a balloon to measure fluctuations in the microwave radiation left behind by the acoustic waves. "We have seen the ripples of the sounds of the big bang that nobody has seen before. It is the music of creation," says Phil Mauskopf from Cardiff University, who led the British team involved in the project.

What keeps a bullet on a straight course?
The bullets coming out of the first muskets were literally scattershot. The unevenly shaped lead balls bounced against the inside of the barrel as they were launched and could easily veer off. Gunmakers solved the problem by improving the fit between bullet and barrel and by placing spiral grooves inside the barrel to spin the bullet as it emerged.  Spinning, like a gyroscope, corrects irregularities in an object's flight path. Finally, in the mid-19th century, bullets were aerodynamically redesigned. They were made longer, ending in the familiar conical tip which puts the bullet on the straight and narrow.
(Source: READER'S DIGEST HOW IN THE WORLD)

How does the silencer on a gun work?
To fire a bullet from a gun, gunpowder is ignited behind the bullet. The gunpowder creates a high-pressure pulse of hot gas. The pressure of the gas forces the bullet down the barrel of the gun. When the bullet exits the end of the barrel, it's sort of like uncorking a bottle. The pressure behind the bullet is immense, however - on the order of 3,000 PSI - so the pop that the gun makes as it is uncorked is extremely loud. A silencer screws on to the end of the barrel and has a huge volume compared to the barrel (20 or 30 times greater). With the silencer in place, the pressurized gas behind the bullet has a big space to expand into. So the pressure of the hot gas falls significantly. When the bullet finally exits through the hole in the silencer, the pressure being uncorked is much, much lower - perhaps 60 PSI. Therefore the sound the gun makes is much lower. Interestingly, a bullet that travels at supersonic speeds cannot be silenced because the bullet creates its own little sonic boom as it travels. Many high-powered loads travel at supersonic speeds. The silencer can remove the "uncorking" sound, but not the actual sound of the bullet's flight.

How are enormously heavy steel ships able to float?
They appear to defy basic laws of nature. But in fact, they're obeying a law of nature, buoyancy, which Greek mathematician Archimedes reportedly discovered while taking a bath.  The trick in building ships so that they don't go straight to the bottom is to get the shape right. The vessel has to be configured so that it will be buoyant, displacing a volume of water weighing as much as it does. In other words, if an amount of steel equal to that in a giant tanker were rolled into a compact ball and dropped into the sea, bye, bye ball. But if the metal is spread out over a thousand feet, the ship can cross the ocean.
(Source: READER'S DIGEST HOW IN THE WORLD)

How much energy does matter contain?
Albert Einstein's most famous formula is widely known: E=mc^2, which relates mass to energy. It says that the energy contained in matter is equal to its mass times the speed of light squared. Since light travels very fast (300,000 kilometers per second, or 186,000 miles per second), there's a lot of energy wrapped up in a very small bit of matter. The energy of one gram (1/28 ounce) of matter would keep a 100-watt light bulb glowing for 28,500 years. One of the most noticeable examples of the mass-energy relation is in the sun, where hydrogen is converted into helium by nuclear fusion. During the reaction, 0.7% of the hydrogen's mass is released as various forms of energy. A tiny fraction of that energy keeps the Earth from turning into a ball of ice.

How do you crack a whip?
A whip makes a cracking sound because its tip moves faster than the speed of sound.

IS IT TRUE THAT ASTRONAUTS HAVE NO WEIGHT WHILE IN SPACE?
Astronauts are not weightless while orbiting the earth. They are, in effect, in constant free fall. If the space shuttle were to stop its forward motion, it would drop, quite heavily. But its thrust carries it forward while gravity tugs down at it, keeping it from shooting into space.

What is a sonic boom?
Sonic booms are not often heard these days in most inhabited parts of the world. That's because they can be somewhat destructive, not to mention annoying. They are caused by aircraft that travel faster than the speed of sound.  The sonic boom is a shock wave that forms when the aircraft's speed outstrips the ability of air molecules to get out of the way. It's a moving pressure wave that starts at the nose, wingtips, and other forward-projecting parts of the aircraft and forms a cone trailing back from the plane and expanding up, down, and out to the sides.  When that cone-shaped pressure field passes across a point on the ground, a sonic boom is heard. Since the pressure wave of a moderate sonic boom can be enough to break windows, non-military aircraft are no longer allowed to travel faster than sound near inhabited areas.

What is special about laser beams?
Laser stands for "Light Amplification by Stimulated Emission of Radiation." A laser beam is produced when light bounces back and forth between two mirrors with a special medium (gas, liquid, or solid) between them. As it bounces, the light triggers energized atoms in the medium to release more light, some of which leaks out through one of the mirrors to produce the laser beam.  A laser beam is special because all the photons (discrete "particles" of light energy) in the beam are vibrating in exactly the same lockstep way. The beam is tightly focused and perfectly aligned because all the photons are "marching in phase" like soldiers in a troop.  In an ordinary beam of light, the photons vibrate every which way.  Because laser photons are in phase, the beam can stay aligned for very long distances and it can be focused down to a very tiny spot without losing its alignment.