Physico-theology

by William Derham

What Mr. Romer’s Hypothesis is, may be seen in the Phil. Transact. before-cited: As also in the before commended Sir Isaac Newton’s Opticks: Light is propagated from luminous Bodies in time, and spends about seven or eight Minutes of an Hour in passing from the Sun to the Earth. This was first observed by Romer, and then by others, by means of the Eclipses of the Satellites of Jupiter. For these Eclipses, when the Earth is between the Sun and Jupiter, happen about seven or eight Minutes sooner than they ought to do by the Tables; and when the Earth is beyond the ☉, they happen about seven or eight Minutes later than they ought to do: The reason being, that the Light of the Satellites hath farther to go in the latter Case than in the former, by the Diameter of the Earth’s Orbit. Newt. Opt. L. 2. Part. 3. Prop. 11.

Now forasmuch as the Distance between the Sun and the Earth (according to the Computations in my Astro-Theology, B. 1. ch. 3. Note 2.) is 86051398 English Miles; therefore, at the rate of 7½ Minutes, or 450 Seconds in passing from the Sun, Light will be found to fly above 191225 Miles in one Second of Time.

[f] Dr. Hook Post. Works. Lect. of Light, pag. 76.

[g] For the proof of this vast Extent of Light, I shall take the Computation of the same great Man, pag. 77. If, saith he, we consider first the vast Distance between us and the Sun, which from the best and latest Observations in Astronomy, is judged to be about 10000 Diameters of the Earth, each of which It about 7925 English Miles; therefore the Sun’s distance is 7925000 Miles; and if we consider that according to the Observations, which I published to prove the Motion of the Earth, [which were Observations of the Parallax of some of the fixt Stars in the Head of Draco, made in 1699] the whole Diameter of the Orb, viz. 20000, made the Subtense but of one Minute to one of the fixt Stars, which cannot therefore be less distant than 3438 Diameters of this great Orb, and consequently 68760000 Diameters of the Earth: And if this Star be one of the nearest, and that the Stars that are of one Degree lesser in Magnitude (I mean not of the Second Magnitude, because there may be many Degrees between the first and second) be as much farther; and another sort yet smaller be three times as far; and a fourth four times as far, and so onward, possibly to some 100 Degrees of Magnitude, such as may be discovered by longer and longer Telescopes, that they may be 100 times as far; then certainly this material Expansion, a part of which we are, must be so great, that ’twill infinitely exceed our shallow Conception to imagine. Now, by what I last mentioned, it is evident that Light extends it self to the utmost imaginable Parts, and by the help of Telescopes we collect the Rays, and make them sensible to the Eye, which are emitted from some of the almost inconceivably remote Objects, &c.——Nor is it only the great Body of the Sun, or the vast Bodies of the fixt Stars, that are thus able to disperse their Light through the vast Expansum of the Universe; but the smallest Spark of a lucid Body will do the very same Thing, even the smallest Globule struck from a Steel by a Flint, &c.

CHAP. V.

Of Gravity.

The last Thing subservient to our Globe, that I shall take notice of, is Gravity[a], or that Tendency which Bodies have to the Centre of the Earth.

In my Astro-Theology, Book 6. Ch. 2. I have shewn of what absolute Necessity, and what a noble Contrivance this of Gravity is, for keeping the several Globes of the Universe from shattering to Pieces, as they evidently must do in a little Time by their swift Rotation round their own Axes[]. The Terraqueous Globe particularly, which circumvolves at the rate of above 1000 Miles an Hour[c], would by the centrifugal force of that Motion, be soon dissipated and spirtled into the circumambient Space, was it not kept together by this noble Contrivance of the Creator, this natural inherent Power, namely, the Power of Attraction or Gravity.

And as by this Power our Globe is defended against Dissipation, so all its Parts are kept in their proper Place and Order. All material Things do naturally gravitate thereto, and unite themselves therewith, and so preserve its Bulk intire[d]. And the fleeting Waters, the most unruly of all its Parts, do by this means keep their constant æquipoise in the Globe[e], and remain in that Place which, the Psalmist saith, God had founded for them; a bound he had set, which they might not pass; that they turn not again to cover the Earth, Psal. civ. 8, 9. So, that even in a natural Way, by virtue of this excellent Contrivance of the Creator, the Observation of the Psalmist is perpetually fulfilled, Psal. lxxxix. 9. Thou rulest the raging of the Sea; when the Waves thereof arise, thou stillest them.