IS FITZGERALD CONTRACTION REAL? 33 



theory, contains many statements which we should 

 express differently in relativity physics. 



Is it really true that a moving rod becomes shortened 

 in the direction of its motion? It is not altogether easy 

 to give a plain answer. I think we often draw a dis- 

 tinction between what is true and what is really true. A 

 statement which does not profess to deal with anything 

 except appearances may be true; a statement which is 

 not only true but deals with the realities beneath the 

 appearances is really true. 



You receive a balance-sheet from a public company 

 and observe that the assets amount to such and such a 

 figure. Is this true? Certainly; it is certified by a 

 chartered accountant. But is it really true? Many 

 questions arise; the real values of items are often very 

 different from those which figure in the balance-sheet. 

 I am not especially referring to fraudulent companies. 

 There is a blessed phrase "hidden reserves"; and gen- 

 erally speaking the more respectable the company the 

 more widely does its balance-sheet deviate from reality. 

 This is called sound finance. But apart from deliberate 

 use of the balance-sheet to conceal the actual situation, 

 it is not well adapted for exhibiting realities, because 

 the main function of a balance-sheet is to balance 

 and everything else has to be subordinated to that 

 end. 



The physicist who uses a frame of space has to 

 account for every millimetre of space — in fact to draw 

 up a balance-sheet, and make it balance. Usually there 

 is not much difficulty. But suppose that he happens to 

 be concerned with a man travelling at 161^000 miles 

 a second. The man is an ordinary 6-foot man. So far 

 as reality is concerned the proper entry in the balance- 

 sheet would appear to be 6 feet. But then the balance- 



