When most people hear the name Einstein, the next thought is usually his famous equation, E=mc2. Believe it or not, Einstein’s Nobel Prize was not awarded for this revolutionary discovery, but for his lesser known paper on the Photo-Electric Effect also published in the same year. A good deal of the confusion about Relativity Theory is that most folks think it is one theory. It is actually three different ideas submitted in three different papers. The equation showing the relationship of energy to mass can be found in an addendum he submitted three months after publishing the Special Theory of Relativity in 1905. He began work on the General Theory of Relativity in 1907 and finished it in 1915. With it, he added the effects of gravity to his original equations and revolutionized how we view the makeup of the universe. And then there’s the confusion about that light speed squared business. What’s that all about?
Einstein’s first paper was titled “On the Electrodynamics of Moving Bodies.” This eventually became known as the Theory of Special Relativity. It dealt primarily with how space and time were related, showing that they were actually two descriptions of the same phenomenon known as 4D spacetime. (A description of spacetime and how it differs from 3D space with an added element of time can be found in the article titled “Dimensions.”) It also explained the time dilation between objects that were moving near the speed of light and those that were moving very slow compared to the speed of light.
The paper showed time to be relative to its frame of reference. For example, if you and a buddy are standing in the aisle of a moving jet and tossing a ball back and forth, the two of you seem to be still and the ball seems to be moving at a normal, slow rate of speed. But, to an observer on the ground, the ball, you, your friend, and the jet are all moving at 200 mph. The plane provides you with a different frame of reference than the one the observer on the ground has. Both Galileo and Newton understood this concept and called it an “inertial frame.” Einstein enlarged the inertial frame by stating that everything including you, the jet and the observer on the ground were all moving at speeds far below that of light. When one of the objects in the scenario gets ramped up to light speed, everything changes.
Because of this, no one observer had a privileged frame of reference. In other words, if an event happened and was observed in two different spatial locations, the event might appear to have happened simultaneously to one observer and as two separate events to another observer. The different perspectives were due to each observer’s motion in relation to the event. Therefore, both observations would be correct to each observer respectively. It would be impossible for either observer to claim they saw the event the “right” way.
Just as Einstein’s first paper showed that space and time were two descriptions of one phenomenon, similarly, the addendum to this paper showed that energy and mass were also two descriptions of one phenomenon. Energy and mass are not equal, as is often misquoted. They are intra-convertible. A very small amount of mass can be exchanged for a very large amount of energy, as demonstrated by experiments in atomic and nuclear physics. It’s considered one of the most elegant formulas in all of physics because a few characters demonstrate the complex concepts found in the original equation, which is big enough to fill a blackboard.
Einstein applied this equation to whether or not an object of mass, any mass, could be accelerated to the speed of light. That’s also were the c2 part of the equation comes into play. The whole thing is about speed, not light. Let’s roll a rock to see how that works. It’s a rather large rock, so it takes a good deal of energy to get it rolling. The energy from that initial push is now stored in the rock as kinetic energy, which it dissipates as it rolls. Any additional pushes just store more kinetic energy than the rock can dissipate and now it has velocity. So, when we want to stop the rock from rolling, we have to absorb the extra energy it contains. The kinetic energy is proportional to the speed squared. So, if you give the rock twice the energy it can disperse, it will take four times as much energy to stop it from rolling (twice the energy squared is four times the energy). In Einstein’s equation, c represents the speed of light, emphasis placed on the word “speed.” His famous equation then, is the ratio of the energy required to move a mass proportional to the speed of light squared.
Some content excerpted from The Sage Age – Blending Science with Intuitive Wisdom
© 2008 MaAnna Stephenson
Content may be used freely with proper credit and a link to www.SageAge.net