to a Demonstration, convince you of the Unnaturalness of such a
Supposition, I must put you in mind, that some time ago, when I was
last in the Country with you, I think it was about the latter End of
Autumn, near the Winter Solstice, as we were walking one Evening, I bid
you take notice of the Moon, which was then near setting, and about
two Days old. You may remember, her whole Globe appeared to us very
conspicuously within a manifest Circle. You immediately told me, that
that kind of Phænomenon the Country People called a _Stork_, or the old
Moon in the new one's Arms. This I then endeavoured to explain to you,
and I think made you sensible it was intirely an Effect of the Earth's,
and an Appearance always to be expected at that Time of the Year. The
Earth being then in the State of a Full-Moon to that Part of the lunar
Orbit, and near her Perihelion, at which time, the Earth sends back a
Reflection to the [O]Moon twenty-five times more potent than that of
the Moon to us.
[Footnote O: Their Diameters being nearly as 1 to 5.]
Now the Planet _Venus_, from undeniable Principles of Geometry, is
allowed to be nearly such another Globe as the Earth is; and since the
Earth, as I have just now related, is found to reflect much more Light
to the Moon, by reason of her superior Magnitude, than the Moon can
possibly reverberate to Earth again; and since also 'tis plain, the
Earth has no Light of its own, why then should we imagine _Venus_ to be
endowed with a Lustre, which we can prove to be no more than a similar
Body, and governed by the same Laws as the Earth is?
_Anaximander's_ Mistake, in supposing the Moon in some small Degree
a radiant Body of itself, lay, in not considering, that the faint
Illumination here described, and visible all over her Globe, soon
after almost every Conjunction with the Sun; and probably in Eclipses,
also proceeded from the Earth; but the thing I think is too evident to
expect any sort of Contradiction, therefore I hope you will admit it
as a Truth, and consequently take it for granted, that the planetary
Bodies in general, are meer terrestrial, if not terraqueous Bodies,
such as this we live upon; which is the Thing I have chiefly in this
Letter attempted to demonstrate, or have rather explained; and now
I hope, for the future, you will receive the Idea of a Plurality of
Worlds more favourably, and look upon astronomical Conjectures in a
less ridiculous Light than you used to do, especially since you must
allow, they give our unlimited Imaginations a like all endless Field of
Contemplation, not only full of the wonderful Works of Nature, but also
of a visible Providence.
I think I cannot conclude this Letter to you more properly, than with
the following fine Lines of Mr. _Addison's_ from the _Spectator_, Vol.
VI. No. 465, which I hope you are not so polite as to look upon as an
unfashionable Quotation.
The spacious Firmament on High,
With all the blue ethereal Sky,
And spangl'd Heav'ns, a shining Frame,
Their great Original proclaim:
Th' unwearied Sun, from Day to Day,
Does his Creator's Pow'r display,
And publishes to ev'ry Land
The Work of an Almighty Hand.
Soon as the Ev'ning Shades prevail,
The Moon takes up the wond'rous Tale,
And nightly to the list'ning Earth,
Repeats the Story of her Birth:
Whilst all the Stars that round her burn,
And all the Planets in their Turn,
Confirm the Tidings as they roll,
And spread the Truth from Pole to Pole.
What though, in solemn Silence, all
Move round the Dark terrestrial Ball?
What tho' nor real Voice nor Sound
Amid their radiant Orbs be found?
In Reason's Ear, they all rejoice,
And utter forth a glorious Voice,
For ever singing, as they shine,
"_The Hand that made us is divine_."
_And am_, &c.
LETTER the FOURTH.
_Of the Nature of the heavenly Bodies continued, with the Opinions of
the Antients concerning the Sun and Stars._
_SIR_,
You tell me you begin to be a tolerable good _Copernican_, and would
now be glad to have my Opinion further upon the Nature of the Sun and
Stars, with regard to the Suggestion of their being like Bodies of
Fire. This you say will go a great Way towards confirming you in the
Notion you have begun to embrace of a Plurality of Systems, and a much
greater Multiplicity of Worlds than our little solar System can admit
of. Besides, shewing in a very evident Light, that the Authorities
cited in my first Letter are founded upon the clearest Reason.
_Anaxagoras_, you say, believed the Sun to be a Lump of red-hot
Iron; _Euripides_ thought it a Clod of Gold; and others still more
ridiculously have imagined it to be a dark Body, void of all Heat.
That the Sun is a vast Body of blazing Matter, notwithstanding the
various Opinions of those primitive Sages, will, I think, hardly admit
of a Question: Since the known Warmth of his prolifick Beams, and the
visible Effect of the Burning-glass, puts it quite out of the Power
of our present Set of Senses, at least to argue against it; and how
reasonably we may imagine the Stars to be all of the same or like
Nature, will sufficiently appear from these following Considerations:
First, it is well known to all Mathematicians, that any visible Object
of any determined Magnitude may be reduced to the Appearance of [P]a
physical Point, by removing the Eye of the Observer to a proper or
proportionable Distance from it, within the finite View: And that the
apparent Diameter of every luminous celestial Body, will always be
diminished reciprocally, in Proportion to the Distance from the Eye,
till they become altogether imperceptible.
[Footnote P: What is here meant by a physical Point, is a Point visible
to the naked Eye, which human Art cannot divide; and so far it partakes
of the Property of a mathematical one, which is only to be conceived,
and not seen.]
Thus the Disk of the Sun, which appears to us at Earth under an Angle
of about half a Degree, if seen from the Planet _Saturn_, would appear
not much bigger than the Planet _Venus_ or _Jupiter_, in their most
neighbouring Vicinity does to us; and consequently to an Eye placed
in the Aphelion Point of the Orbit of the great _Comet_ of 1680, his
apparent Diameter would be so reduced as to seem but little bigger than
the largest of the Stars; and by the same Analogy, or Way of Reasoning,
admitting Space and Distance infinite, which I humbly apprehend is
not to be disputed, were all the Matter in the Universe united, and
conglobed in one Mass, with respect to ocular Sensation, it might be
diminished so near to a mathematical Punctum, as to be almost adequate
to our Ideas of Nothing.
This to any tolerable Optician, must be an evident Conviction of the
Truth of the modern Astronomy, which now universally allow all those
radiant Bodies the Stars to be of the same Nature with the Sun; and
that as certainly they are no other than vast Globes of blazing Matter,
all undoubtedly shining by their own native Light.
But as you have often objected to what has been said of the Distance
of the Stars in general, and may possibly from a Supposition, that
they are, or may be, much nearer to us, infer, that their Light, like
that of the Planets, may be also borrowed from the Sun, or from some
other radiant Body, which, from the Nature of the Supposition, must of
Consequence be invisible to us, I judge it will not be amiss to throw
a few demonstrative Arguments in your Way, in order to lead you a
little out of the Path of an early Prejudice, and draw you as it were
by Degrees through the Dawn of astronomical Reasoning, out of your
original Error, and rescue your Imagination from the false Notions
imbibed from Phænomena only in your younger Years. This I guess cannot
fail of reconciling you to this more rational Way of Thinking, and
make you acquainted with Truths of much Consequence, which perhaps
you have yet been an intire Stranger to. The grand _Deceptio Visus_,
which I must first endeavour to remove, and which as a sort of Paradox
in Nature, has, as I may say, imprisoned the Understanding of many
superficial Reasoners, and in general all incurious Men, is this.
Most People are too apt to think originally, that as the Heavens appear
to be a vast concave Hemisphere, that the Stars must of course, as of
Consequence, be fixed there, like so many radiant Studs of Fire, of
various Magnitudes; and take it for granted, chiefly designed for no
other Purpose than to deck and adorn the Canopy of our Night. This was
long ago the Opinion of _Thales_ the _Milesian_, and wants not the
Authority of many of the Antients to back it. Others, in particular
[Q]_Ptolomy_ of _Pelusium_ in _Africa_, who from his Experience in this
Science, is called by some the Prince of Astronomers, believed them
to be Loop-holes in the vast solid celestial Firmament, emitting the
Light of the Crystalline Heaven through it to all within it. The famous
_Diogenes_, Cotemporary with _Plato_, conceived them to be of the
Nature of Pumice-stones, and inclined to an Opinion, that they were the
_Spiracula_, or Breathing-holes of Heaven. _Anaxagoras_ thought them
Stones snatched up from the Earth by the Rapidity of its Motion, and
set on Fire in the upper Regions above the Moon.
[Footnote Q: _Ptolomy_ supposed two Heavens above that of the fixed
Stars, which he called the eighth; _viz._ a ninth, the Crystalline, and
a tenth the _Primum Mobile_. See Letter the second.
The sacred Sun, above the Waters rais'd,
Thro' Heav'ns eternal, brazen Portals blaz'd;
And wide o'er Earth diffus'd his chearing Ray,
To Gods and Men to give the golden Day.
Homer.
]
But how ridiculous and absurd all these Opinions and Conjectures really
are, will easily appear, if we but once consider the Nature of an
unbounded Æther, and the amazing Property of infinite Space.
This, with what has been said before, will not a little assist your
Imagination towards conceiving the Reasonableness of the Notion modern
Astronomers are now confirmed in, of their being absolutely so many
burning Balls, and which was no doubt, many Years ago, the Opinion of
_Manilius_, as is evident from these Lines in his Poem of the Sphere.
For how can we the rising Stars conceive
A casual Production; or believe
Of the chang'd Heav'ns the oft renascent State
_Sol's_[R]frequent Births, and his quotidian Fate.
Sherburne.
And again, in the same Poem:
The fiery Stars, and Æther that creates
Infinite Orbs, and others dissipates.
[Footnote R: _Xenophanes_ believed the Stars to be no other than Clouds
set on Fire, quenched in the Day-time, and rekindled in the Night.]
_Zoroaster_, the first of all Philosophers we read of who studied
the Stars, is reported to have believed them of a fiery Nature.
_Empedocles_ judged them to be Fire æthereal, struck forth in its
Secretion, and blazing in the upper Regions. _Plato_ thought them Fire,
with the Mixture of other Elements as Cements. _Heraclides_ Worlds by
themselves, of _Earth_, _Air_, and _Fire_; and _Aristotle_, simple
Bodies of the Substance of Heaven, but more condensed.
But that I may not take up too much of your Time with Opinions that
has been imbibed in the Infancy of Astronomy, and has long ago been
exploded, I shall attempt but one Thing more to confirm your Sentiments
in this new Doctrine.
First, that the Stars are all at a Distance, not to be determined by
the utmost Perfection of human Art, is manifest from their having very
little, or no sensible [S]Parallax; and consequently, that any one of
them is absolutely bigger or less than another, from the simple Laws of
Opticks, cannot possibly come under our Observation to be ascertained;
but that they all of them may be nearly of the same Size or Solidity,
is as impossible, with any Shew of Reason to deny, since it is a known
Principle in Geometry, that all visible Objects naturally diminish,
as has been said before, or are magnified in a certain Proportion to
their Distance from the Eye; and hence we may conclude, and not without
Reason in its strongest Light to support us, that the smallest Stars,
to the very least Denomination, are only removed respectively more
distant from the Observer's Station; and that at least this we may be
certain of, that they are all together undoubtedly an Infinity of like
Bodies, distributed either promiscuously, or in some regular Order
throughout the mundane Space: And, as _Marino_ says,
Resplendent Sparks of the first Fire!
In which the Beauty we admire,
And Light of those eternal Rays,
The uncreated Mind displays.
[Footnote S: Mr. _Bradley_, Astronomer-Royal, has, in a great measure,
proved that the Aberration of the Stars hitherto mistaken for a
Parallax, may arise from, and indeed seems to be no other than the
progressive Motion of Light, and Change of Place to the Eye, arising
from the Earth's annual Motion and Direction.]
It remains now I think to shew, and endeavour to prove, that the Stars
are not only light Bodies of the Nature of the Sun, but that they are
really so many Suns, all performing like Offices of Heat and Gravity,
in a regular Order, throughout the visible Creation, in opposition to
an Opinion you have formerly hinted at, of their being in another
Sense of a secondary Nature.
All Objects within the sensible Sphere of the Sun's Attraction, or
Activity, are in some measure magnified by a good Telescope: But the
Stars are all placed so far without it, that the best Glasses has no
other Effect upon them than making them appear more vivid or lively,
but all innate opaque Bodies, reflecting only a borrowed Light from
some primary one, contrary to this Property, are all observed to lose
their Light, in the same Proportion, as they are magnified, and through
all Glasses become more dull than otherwise they appear to the naked
Eye: And hence we may infer, without any further Evidence, that the
Stars are all light Bodies endowed with native Lustre; and that Bodies,
like the known Planets, from the same Reasoning, it is as clear they
cannot be, because their Distance, though uncertain as to the Truth of
the whole, yet such a Part of it as cannot be denied, would render them
all in such a Case invisible.
A Proof of this will plainly present itself, if we consider the Course
of the known Comets, who all of them, without Exception, become
imperceptible, and intirely disappear; though most of them much bigger
than the Earth, or any of the lesser Planets, long before they arrive
at their respective Aphelions.
But we are under a kind of Necessity to believe them either Suns or
Planets, that is either dark or light Bodies; and since I have shewn
the Improbability; nay, I may venture to say, the Impossibility of
their being the first, it is natural sure to conclude, that they must
be of the last Sort; and I am persuaded, if you but once consider how
ridiculous it is to imagine so vast a Number of Bodies, all rolling
round a Number of invisible Suns, which must otherwise be the Case,
since they are seen on all Sides of ours, and cannot possibly be
enlightened by him, or any, how all of them, by any one else, you
cannot possibly have any sort of Difficulty in this Determination:
But that no Arguments may be wanting to enforce your Belief of what
is here concluded, it will not be amiss to put you in Mind of an
optical Experiment or two, which cannot fail of convincing you of
the vast Probability of what is here asserted of them; and next to a
moral Certainty, demonstrate the Truth of what so many of the best
Astronomers have advanced, as before namely, that the Stars are all, or
most of them, Suns like ours.
Place any concave Lense before your Eye, and you will find all visible
Objects will appear through it, as removed to a much greater Distance
than they really are at, and reciprocally as much diminished. Now, if
you look upon one of these Glasses of a proper Concavity, opposed to
the Sun or Moon, you will respectively have the Appearance of a real
Star or Planet, the first exhibited by the Body of the Sun, the other
by the Moon, and either more or less diminished in Proportion to the
Surface of the Sphere the Glass is ground to.
For Example, a double Concave, or Glass of a negative Focus, ground to
a Sphere of about three Inches Diameter, will if opposed to the Sun's
Disk at a proper Distance from the Eye, help you to a very good Idea
how the Sun appears to the Planet _Jupiter_; and if a proper Regard be
had to the Distance of the Planet _Saturn_, a Lense still more concave
may be formed to give a just Idea of the Sun's Appearance to _Saturn_.
Again, one much more concave than the former, proportioned to the Orbit
of _Mars_, will naturally exhibit the solar Body, as seen from that
Planet.
To the Planet _Venus_ and _Mercury_, the Sun appearing much larger
than to us at the Earth, to have any tolerable Notion of his varied
Phænomena to them, it will be necessary to procure Glasses of a
suitable Convexity, ground to reciprocal Concaves, which may easily be
done to any Focus, so as to shew how the Sun, naturally appears to the
Inhabitants of those two Planets.
The various Appearances of the Planets themselves to us at the Earth,
may also well enough be had, if through Glasses analagous to their
respective Distance and Magnitude, we look at the Moon, particularly
all the Phases of _Venus_, and even of _Mercury_, and the Gibosity of
_Mars_, &_c._ may be justly and beautifully represented at different
Ages of the Moon, as those Planets appear through the largest and best
Telescopes.
This Way you may convince even your Friend * * *, who you tell me has
reasoned all his Senses useless, and yet continues so great an Atheist
in Astronomy, as not to believe the World turns round upon its Axis,
though he gives no better Reason for it than that of his not being
giddy.
After all these Arguments, I hope no new Difficulties will arise to
retard your Belief, or deprive the Stars of their solar Nature, so
justly due to them: This Point gained, the next Thing to be considered
is, whether all those glorious Bodies, the far greater Part of whom
being invisible to the naked Eye, were made purely and purposely for
the sole Use of this diminitive World, our little trifling Earth.
----Men, conceited Lords of all,
Walk proudly o'er this pendent Ball,
Fond of their little Spot below,
Nor greater Beings care to know,
_But think those Worlds, which deck the Skies,
Were only form'd to please their Eyes_.
Duck.
The very Supposition not only implies a profound Ignorance of the
Divine Attributes, but is as impious, and full of Vanity, as it is
erroneous and absurd, and even a Blindness sufficient of itself, were
there no other Cause for it, to introduce Idolatry in the Minds of
Mortals, by sinking the divine Nature so near to the human.
It being granted that the Stars are all of the same Kind, I think it
may be agreed, that what we evince of any one may be allowed to be
true of any other, and consequently of all the rest. This _Postulata_
gained, I shall next proceed to enquire what the real Use and Design of
so many radiant Bodies are, or may be made for.
The Sun we have justly reduced to the State of a Star, why then in
Reason should he have his attendant Planets round him, more than any of
the rest, his undoubted Equals? No Shadow even of a Reason can be given
for such an Absurdity.
May we not with the greatest Confidence imagine, that Nature as justly
abhors a _Vacuum_ in Place, as much as Virtue does in Time? Surely
yes: And by supposing the Infinity of Stars, all centers to as many
Systems of innumerable Worlds, all alike unknown to us; how naturally
do we open to ourselves a vast Field of Probation, and an endless
Scene of Hope to ground our Expectation of an _ever_-future Happiness
upon, suitable to the native Dignity of the awful Mind, which made and
comprehends it; and whose Works are all as the Business of an Eternity?
If the Stars were ordained merely for the Use of us, why so much
Extravagance and Ostentation in their Number, Nature, and Make? For
a much less Quantity, and smaller Bodies, placed nearer to us, would
every Way answer the vain End we put them to; and besides, in all
Things else, Nature is most frugal, and takes the nearest Way, through
all her Works, to operate and effect the Will of God. It scarce can be
reckoned more irrational, to suppose Animals with Eyes, destined to
live in eternal Darkness, or without Eyes to live in perpetual Day,
than to imagine Space illuminated, where there is nothing to be acted
upon, or brought to Light; therefore we may justly suppose, that so
many radiant Bodies were not created barely to enlighten an infinite
Void, but to make their much more numerous Attendants visible; and
instead of discovering a vast unbounded desolate Negation of Beings,
display an infinite shapeless Universe, crowded with Myriads of
glorious Worlds, all variously revolving round them; and which form
an Atom, to an indefinite Creation, with an inconceivable Variety of
Beings and States, animate and fill the endless Orb of Immensity.
That the sidereal Planets are not visible to us, can be no Objection to
their actual Existence, and being there, is plain from this; it is well
known, that the Stars themselves, which are their Central, and only
radiant Bodies, are little more to us at the Earth, than mathematical
Points. How ridiculous then is it to expect, that any of their small
opaque Attendance, should ever be perceived so far as the Earth by
us; and besides, to show the Impossibility of such a Discovery, we
need only consider, what is, and what is not to be expected, or known
in our own home System. All the Planets in this our sensible Region,
every Astronomer knows, is far from being visible to one another, in
every individual Sphere; for to an Eye at the Orb of _Saturn_, this
Earth we live upon, which requires Years to circumscribe, and Ages to
be made acquainted with, and is far from being yet all known, cannot
possibly from the above Planet be seen: And further, since _Saturn_ and
_Jupiter_, two of the most material and considerable Globes we know of,
except the Sun himself, are Bodies apparently of the same kind, and are
observed to have each a Number of lesser Planets moving round them; why
may we not expect with equal Certainty and Propriety, that all other
Bodies, under the same Circumstances, are in like manner attended; that
is, seeing the Sun is found to be the Center of a System of Bodies, all
variously volving round him? where lies the Improbability of his fellow
Luminaries, the Stars, being surrounded in like sort, with more or less
of such Attendance.
I shall offer but one Thing more to your Consideration in this Affair,
and which I am in great Hopes will be sufficient to make you think
these natural Suggestions a good deal more than probable, and that is
this:
The modern Astronomers having, in a great measure, proved that the
Stars are, in all respects, vast Globes of Fire like our Sun. Let us
suppose a new-created Mind, or thinking Being, in a profound State of
Ignorance, with regard to the Nature of all external Objects, but fully
endowed with every human Sense and Force of Reason, suspended in Æther,
exactly in the midway, betwixt [T]_Syrius_ and the Sun; in which Case,
both of these Luminaries would equally appear much about the Brightness
of the largest of our Planets. Now should such a Being, determined
either by Accident or Choice, arrive at this our System of the Sun, and
seeing all the planetary Bodies moving round him, I would ask you what
you think he would imagine to be round _Syrius_? Your Answer, I think I
may venture to say, would not be _nothing_; and methinks I already hear
you say, Why Planets such as ours.
[Footnote T: A Star of the first Magnitude in the greater _Dog_, and
the most neighbouring to our Sun.]
PLATE XI.
Is designed as a geometrical Scale to all the primary Parts of the
visible Creation, with regard to the Distance of Orbits compared with
the Globe of the Sun; by which at once may be conceived, and justly
measured in the Mind, not only the mean Distance of the Planets with
regard to one another, but also that of the Comets, and even the
comparative Distances of the nearest of the Stars, which will, I guess,
greatly help you to form an Idea of the vast Extent of Space necessary
to comprehend the whole Creation.
_Fig._ 1. Is a Radius of the Orbit of _Mercury_, in true Proportion to
the Body of the Sun represented at S, shewing at the same time a small
Portion of the opaque Planet's Orbit, and the real Length of its Shadow
at P.
_Fig._ 2. Is a Radius of the whole System of the Planets as far as the
Orbit of _Saturn_ in Proportion to a compleat Orbit of _Mercury_, much
less than the former; the former serving as a better known Scale to
consider the amazing Distances of the more remote Planets by.