Caverni, Raffaello, Storia del metodo sperimentale in Italia, 1891-1900

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            <p type="main">
              <s>
                <pb xlink:href="020/01/1103.jpg" pagenum="546"/>
              Ora, per legge astronomica, negli afelii i Pianeti debbono andare più lenti,
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              e nonostante per legge meccanica hanno più validi impulsi, perch'essendo
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                <figure id="id.020.01.1103.1.jpg" xlink:href="020/01/1103/1.jpg" number="173"/>
              </s>
            </p>
            <p type="caption">
              <s>Figura 105.
                <lb/>
              le velocità de'fluidi in ragion reci­
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              proca delle sezioni, per gli spazii AB,
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              BC, più angusti degli spazii DE, FE,
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              la materia vorticosa deve moversi più
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              veloce. </s>
              <s>“ Quae duo repugnant inter
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              se ” (Editio cit., pag. </s>
              <s>421). </s>
            </p>
            <p type="main">
              <s>Gl'impulsi iniziali secondo l'ipo­
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              tesi platonica, rinverdita di nuove
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              fronde da Galileo, non si poteva ora­
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              mai più ammettere, essendo stato di­
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              mostrato di fatto che i moti de'Pia­
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              neti non sono uniformi ne'circoli
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              perfetti, e dall'altra parte non aveva
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              alcuna specie di probabilità l'ipotesi
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              immaginata dal Boulliaud de'circoli equanti. </s>
              <s>Fu perciò che il Newton pensò
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              felicemente di tornare alle antiche idee pitagoriche, secondo le quali il moto
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              e la traiettoria della Luna si rassomigliava al moto e alla traiettoria della
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              pietra gittata. </s>
              <s>“ Lapis proiectus, urgente gravitate sua, deflectitur de cursu
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              rectilineo et curvam lineam in aere describendo, tandem cadit in Terram. </s>
              <s>
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              Si motu velociore proiiciatur, pergit longius. </s>
              <s>Augendo velocitatem fieri pos­
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              set ut arcum describeret milliaris unius, duorum, quinque, decem, centum,
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              mille, ac tandem ut pergendo ultra terminos Terrae non amplius in Terram
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              caderet ” (De Mundi syst. </s>
              <s>cit., pag. </s>
              <s>6, 7). </s>
            </p>
            <p type="main">
              <s>Lo splendor del pensiero, che balena condensato dentro queste parole,
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              si riflette, come luce di specchio in specchio, da una in altra delle varie
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              proposizioni dimostrate nel Lib. </s>
              <s>I dei Principii matematici di Filosofia na­
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              turale. </s>
              <s>Data la forza equabile di proiezione e l'acceleratrice verso il centro,
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              in modo però che gli additamenti d'impulso sieno costantemente proporzio­
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              nali ai tempi, e perciò, per le brevi distanze prese sulla superficie terrestre,
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              dato che le forze attrattive sieno invariabili, il proietto scagliato descrive una
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              parabola. </s>
              <s>“ Hoc est theorema Galilaei ” (Propos. </s>
              <s>X, pag. </s>
              <s>149). </s>
            </p>
            <p type="main">
              <s>Supponiamo ora, seguitava così a ragionare il gran Filosofo, di avere
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              una Forza onnipotente, la quale sia capace di gettar la Luna o altro più
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              ponderoso Pianeta per l'immensità del Cielo, come la nostra mano getta
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              una pietra per l'aria. </s>
              <s>Supponiamo inoltre che quello smisurato Globo così
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              lanciato, per esser tanto lontano dal centro del proprio moto, vi sia attratto,
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              non con forza costante, ma variabile reciprocamente ai quadrati delle di­
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              stanze. </s>
              <s>Descriverà egli ancora una parabola, come nel teorema di Galileo, o
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              una curva diversa? </s>
              <s>E la risposta, conclusa da alcune proposizioni prece­
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              dentemente dimostrate, era questa: ” Movebitur hoc corpus in aliqua sectio­
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              num conicarum, umbilicum habente in centro virium ” (Prop. </s>
              <s>XIII, pag. </s>
              <s>161). </s>
            </p>
            <p type="main">
              <s>Quel corpo dunque, come in una parabola, così potrebbe rivolgersi bene </s>
            </p>
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