IMG69

Ernst Much

minek were locatcd in living brains, and all such brnins cxistcd i_n “absolutc space.” Mach’s objcctions to other “absolutcs," such as ti_mCt motion, place, and rest, were basically the same as those against absolutc space, but should secm plausiblc only to peoplc who think that relations or what arc related have to be consciously noticcable to be real or “scientific.”

Herc arc somc quotations rcflccting Mach’s opposition to Ncwton*s understandingof space, time, and motion:

It would appear as though Newton in the rcmarks herc citcd still stood under the influence of the mcdicval philosophy, as though hc had grown unfaithful to his re$olvc to investigate only actual facts.⁶¹

A motion may, with rcspect to another motion, be uniform. But the qucstion whether a motion is in itself uniform, is scnsclcss. With just as littlc justicc, also, may we speak of an “absolutc time”—of a time independent of change. This absolutc time can be mcasured by comparison with no motion, it has thcreforc neither a practical nor a scicntific valuc; and no one is justified in saying that he knows aught about it. It is a meta-physical conception.⁶²

It is utterly bcyond our power to measure the changes of things by time. Quitc the contrary, time is an abstraction, at which we arrive by mcans of the changes of things. m3dc bccausc we arc not rcstricted to any one definite measure, all bcing intcrconncctcd.⁶³

No one is compctent to prcdicatc things about absolutc space and absolutc motion; they arc pure things of thought, purc mcntal constructs, that cannot be produccd in cxpericnce. All our principles of mcchanics are, as we havc shown in dctail, cxpcrimental knowlcdge conccrning the rclative positions and motions of bodies.⁶⁴

No one is warranted in cxtcnding thcsc principles [of mcchanics] bcyond the boundaries of expcriencc. In fact, such an c.Mcnsion is mcaningless, no one possesses the rcquisitc knowlcdge to make usc of it/⁶

It is scarcely nrrrssary to remark that in the rcflcctions herc presented Newton has again actcd contrary to his cjcpresscd intention only to investi-gatc actual facts.™

A thing that is beyond the ken of knowlcdge, a thing that cannot be cxhibitcd to the senses, has no mcaning in natura! science.⁶⁷

Ali physical determinations are relalit/e. Conscqucntly, likcwise all geo-me tri cal determinations possess validity only rclativcly to the measure. The conccpt of mcasurcmcnt is a concept of relation, which contains nothing not containcd in the measure.⁶*

Mach also opposcd other “absolutcs’' such 3s “absolute zero” and “the absolutc speed of light.”⁶⁰ It is possiblc hc opposcd other scicntific con-ioo

sunts as wdl. The only "absolutcs" hc sccms to havc favorcd were the "absolutc ccrtainty” that sensations were "immcdiatcly givcn " that in and of thcmschcs they could not be dcccptivc, and that depending on the way in which they were related they cómiilulćd the cxtcinal world.

VI

Newton attempted to support his argument for the rcality of absolutc motion by appealing to what has bcen callcd "the buckct experimcnt”:

If a vcssd hang by a long cord is so often turncd about that the cord is strongly twisted, then fillcd with water and hcld at rest together with the water, thcrcupon by the sudden action of another forcc it is whirlcd about the contrary way, and while the cord is untwisting itself the vessel continues for somc time in this motion, the surfacc of the water will at Lrst be plain, as beforc the vcsscl began to move; but after the vesscl, by gradually communicating its motion to the water, will make it begin sensibly to rcvo!ve and recedc by littlc and little from the middle, and asccnd to the sides of the vcsscl, forming icsclf into a concavc figurę (as 1 havc cxpcrienccd); and the swifter the motion bccomcs, the higher will the water risc, till at last, performing its revolutions in the same times with the vcsscl, it bccomcs relativcly at rest in it. This ascent of the water shows its endcavor to recedc. from the axis of its motion; and the truć and absolutc motion of the water, which is herc directly contrary to the rclatwe, bccomcs known and may be measured by this endcayor.⁶⁰

The effeets which distinguish absolute from rclativc motion are the forccs of reccding frorn the axis of circular motion. For thcrc arc no such forces in a circular motion purcly relative, but in a truć and absolutc circular motion they are greater or less according to the quantity of the motion.⁰¹

There is only one rcal circular motion of any one revolving body, cor-responding to only one power of endcavoring to recedc from its axis of motion, as its proper and adequate cffcct; but relative motions, in one and the same body, arc innumerablc, according to the various relations it bcars to extcrnal bodies, and, likc other relations, are altogcthcr destitutc of any real cffcct, any otherwise than they may perhaps partakc of that one only true motion.⁶²

Mach responded ingcniously to the challenge: first by inquiring whether Ncwton's water results wóuld follow if the buckct were sev-cral leagues thick; second, by suggesting that the stars could as easily be interpreted as rcvolving around the stationary buckct as the buckct spinning under fixcd or rclatively fixed stars; and third, by returning to the arguments of Cardinal Bcllarmine against Galileo'* defense of the Copernican theory as a theory of reality.¹' In Mach*s own words:

ioi