All About Light All About Light Main Page  Classical  Relativistic  Quantum 



On the previous page we set up a competition between Albert the Smart and Arthur the Muscle for half the kingdom and the princess. On this page I explain Albert's thoughts how to win.
When you measure the length of a moving object, relativity theory dictates that the length is contracted. For example, suppose you have a strudel sitting on your table and you measure its length as 1 meter. If the strudel moves and passes a stationary observer, this observer will not measure 1 meter, but less, depending on the speed of the strudel. The higher the speed, the shorter the object. This contraction occurs only in the direction of motion: in any other direction, the dimensions of the object will not change. So, Albert wins by making the strudel move with a very high speed. The strudel will contract, so its length, as measured by the people in the throne room, is 50 meters. How does Albert prove that the strudel will fit to the throne room? (Please follow the picture) Remember, Albert has installed two doors. Let's call them front door F and back door B.
Conclusion: Albert the Smart wins the competition. Let's look at this issue also from the point of view of an observer tied to the moving strudel. From his point of view, the throne room moves with a very high speed toward the strudel: therefore, the distance between the front and back doors F and B contracts to 1/10 of its size, which means that the distance between F and B is 5 meters. So, for the observer tied to the strudel, the strudel would not fit in the throne room. Wait a minute: for one observer the strudel fits, and for the other one does not? This seems to be a paradox. Please read the solution to this paradox on the next page. 

back next  

last modified 1/5/2001 email Fermilab 