The Einstein Theory of Relativity

Jan 27, 2016

A Con­cise State­ment by Prof. H. A. Lorentz, of the Uni­ver­sity of Ley­den

The total eclipse of the sun of May 29, re­sulted in a strik­ing con­fir­ma­tion of the new the­ory of the uni­ver­sal at­trac­tive power of grav­i­ta­tion de­vel­oped by Al­bert Ein­stein, and thus re­in­forced the con­vic­tion that the defin­ing of this the­ory is one of the most im­por­tant steps ever taken in the do­main of nat­ural sci­ence. In re­sponse to a re­quest by the ed­i­tor, I will at­tempt to con­tribute some­thing to its 6gen­eral ap­pre­ci­a­tion in the fol­low­ing lines. For cen­turies New­ton’s doc­trine of the at­trac­tion of grav­i­ta­tion has been the most promi­nent ex­am­ple of a the­ory of nat­ural sci­ence. Through the sim­plic­ity of its basic idea, an at­trac­tion be­tween two bod­ies pro­por­tion­ate to their mass and also pro­por­tion­ate to the square of the dis­tance; through the com­plete­ness with which it ex­plained so many of the pe­cu­liar­i­ties in the move­ment of the bod­ies mak­ing up the solar sys­tem; and, fi­nally, through its uni­ver­sal va­lid­ity, even in the case of the far-dis­tant plan­e­tary sys­tems, it com­pelled the ad­mi­ra­tion of all.

But, while the skill of the math­e­mati­cians was de­voted to mak­ing more exact cal­cu­la­tions of the con­se­quences to which it led, no real progress was made in the sci­ence of grav­i­ta­tion. It is true that the in­quiry was trans­ferred to the field of physics, fol­low­ing Cavendish’s suc­cess in demon­strat­ing the com­mon at­trac­tion be­tween bod­ies with which lab­o­ra­tory work can be done, but it al­ways was ev­i­dent that nat­ural phi­los­o­phy had no grip on the uni­ver­sal power of at­trac­tion. While in elec­tric ef­fects an in­flu­ence ex­er­cised by the mat­ter placed be­tween bod­ies was speed­ily ob­served—the start­ing-point of a new and fer­tile doc­trine of elec­tric­ity—in the case of grav­i­ta­tion not a trace of an in­flu­ence ex­er­cised by in­ter­me­di­ate mat­ter could ever be dis­cov­ered. It was, and re­mained, in­ac­ces­si­ble and un­change­able, with­out any con­nec­tion, ap­par­ently, with other phe­nom­ena of nat­ural phi­los­o­phy.

Ein­stein has put an end to this iso­la­tion; it is now well es­tab­lished that grav­i­ta­tion af­fects not only mat­ter, but also light. Thus strength­ened in the faith that his the­ory al­ready has in­spired, we may as­sume with him that there is not a sin­gle phys­i­cal or chem­i­cal phe­nom­e­non—which does not feel, al­though very prob­a­bly in an un­no­tice­able de­gree, the in­flu­ence of grav­i­ta­tion, and that, on the other side, the at­trac­tion ex­er­cised by a body is lim­ited in the first place by the quan­tity of mat­ter it con­tains and also, to some de­gree, by mo­tion and by the phys­i­cal and chem­i­cal con­di­tion in which it moves.

It is com­pre­hen­si­ble that a per­son could not have ar­rived at such a far-reach­ing change of view by con­tin­u­ing to fol­low the old beaten paths, but only by in­tro­duc­ing some sort of new idea. In­deed, Ein­stein ar­rived at his the­ory through a train of thought of great orig­i­nal­ity. Let me try to re­state it in con­cise terms.