Show astronomical tal LECTURES I 1 by rrok ORSON PRATT lecture I 1 E C T URE S E C 0 ND in our last lecture it was demonstrated that the eth earth e th is of a globular form and of a determinate magnitude that it exists without any external supports or foundations surrounded on au all a sides ides by space and that bodies can exist on a ill I 1 I 1 sides of its surface without any danger of falling away from it we nw now proceed to investigate the grand and important question whether the earth be at rest or in I 1 notion motion it is evident that we can never malic make any considerable sid erable advance in astronomy until this question i is titus determined we perceive nothing in the constitution con of the earth which disqualifies it for motion its shape and magnitude can be no obstacle the qualities and proportions of its various elements and compounds do not render it immovably the atmosphere by which it is enveloped I 1 and the internal forces within do not effect its mobility jn in the least if the spaces surrounding the earth on all ades be empty and void of substance there can be no external resistance offered to its i ts moti notions ons under such circumstances the earth must maist ha be free to yield W the slightest pressure or impulse from froin without and the result of such pressure or impulse I 1 i would necessarily be motion however feeble aud and imperceptible to us it I 1 is s 1 impossible for us to judge whether the earth I 1 be at re rest st or in motion by our feelings when a ship is becalmed on a smooth sea it will freau frequently antly swing round so as to head in different directions no one would be sensible aen sible of this rotation reference to some external object no one has felt any motion ii iche ship were wafted wafred along by unknown currents at the I 1 late ate of 5 miles per hour no one would perceive the motion but might fancy themselves thern selves at rest until by an observation on the heavenly bodies they detected such motion A person in a i balloon if wafted wafred by a havy yet steady g gale ale at the rate of 69 60 miles an hour would feel no action of the wind aird might suppose himself at erret rest in a calm until by a reference to the surface of the earth lie he perceives hi his ts great velocity I 1 the the e earth ah with all it contains ains might fly in pice p with it any ny conceivable velocity however r great I 1 ind aid no one ti ne upon the earth would know whether he were a at t r rest est or in motion unless by a reference to eternal objects the earth might havea have a rot L t abill or wv no ement upon an ax axis is unperceived b by as 1 and which could only bp be detected d te ted by the most careful ci reful observations experiments A As a man passing down a river carried by bv a swift a snoots current ald would be abl obliged ig e d to rf r fer t the shore re to determine whether he were in motion so an a nan inan who would satisfy himself whether the earth be in motion must ref refer er to objects in the heavens heave na unconnected with the earth if the heavenly bodies constantly shift their position in regail to the earth lie h is forced to conclude cn clude that iq either r the heavenly bodies themselves ire in real rt al motion or else if inthey they ire are stationary thi that lit the earth mus must it be in motion or if both be in motion that the phenomenon is the I 1 J result L sult of their relative motions hence it is not easy I 1 to ro conclude from such observations observation alone whether 4 i 1 it be the earth or tile heavens that are really readily inn in motion moi I 1 bv referring to the starry heavens above us we see them all apparently in motion from east to west let any one who wishes to view this magnificent benery and bee become 0 me acquainted with the apparent notions of the stars station himself on some clear evening in in a convenient position facing the south let him fix his attention atte upon those stars which are I 1 near the southern s horizon and lie he will perceive that they will not remain long above the horizon they arise i just east of the point poin t where the meridian cuts the southern horizon ascend gradually to the meridian idian where they attain their greatest altitude and then gradually descend and finally set get at a small angular di distinct west of the meridian during rin gathe the short I 1 t time of their visibility they appear to describe only the small upper segment of their diurnal I 1 circle let him next turn his hig attention to that quarter of the horizon between the south and east and he will behold a success succession iori of stars and clusters of stars rising one after another as if they came out of the earth at different points along the horizon the far ther their rising point is from the south the larger willae will he the sem segments ments of their circles which they will describe above c me ilie horizon and the greater will tie be the length of time that they will remain insight in sight fach each star will attain its greatest altitude on the meridian and will set precisely as many degrees to the westward of south as they rose p to the eastward those stars that rise exactly in the east will set exactly in the west and will describe a semicircle nearly in 12 hours heia he ia 5 tex z jelsa ul m zu joyse awre I 1 abw rise rise between the eastant east and northeast north east points of the horizon and he will fiodi find that hat they remain above the horizon more than 13 hours that the various various segments which they describe are greater than sem ii himles and that they descend behind the western horizon as far fe the north of west as t thay ay rose north of east those stars which come to t 0 the meridian n directly over our heads and whose zenith zenit t not exceed nine degrees north will re remain maj n icove the horizon nearly 24 hours and their visible diurnal axes arcs will be nearly the whole cir f of circles they will sink beloy below ae gnp edge odthe horizon a little to the west boff be hiria ich they will remain only f es and then the they y will rise agi again I 1 I 1 north as they the y set on the I 1 e valance a ance of 0 f the stars in i the thie no noir rUg 1 appear to describe entire i circle v elea point in the heavens en l called 1 d the th eHra 1 a polar point is is on our oar nort northern b rn m Is elevated above the north 1 p t f q ut 40 3 4 degrees being the same atif adde of olour our city all the heavenly bl b i in n 40 34 54 5 4 degrees of this polar point mev aey 11 or set to us in describing their diurnal ciri I 1 alls they hey corpe come to the meridian twice at equal distances n fron from I 1 the pole at which time they aby are a due north of us they approach the upper meridian from the east cast and then gradually descend in s semi emi circles and apparently approach the lower me meridian aidian from the west at which point they begin again to ascend in the semi diurnal arcs which w lay east of the meridian until they again 1 attain their greatest altitude on the upper meridian the polar point jo to be the only one in our northern sky but bat what it a is in apparent motion this point pint is not marked by any stir star but Is is purely an irv mi immovable movable centre A bright alar called the pole star is situated about one and a half it grees from thip ip centre and describes a very small circle around in the same time ti ne and in the same saine manner its as the re it the diurnal circles of the stars seem to grow I 1 1 smaller in in proof proportion tion to their distance either north or south h of the equinoctial line from these ap b 11 0 may expect that there is is another pole of the heavens in mine the south situated directly opposite the north pole being as much depressed below the southern s horizon as our pole is is 1 elevated aboe the northern let any one oi who wishes to satisfy himself upon this subject by observation travel to 19 the south and as a he proceeds to towards w aads the equator he will behold the stars which are just above the northern horizon begin to sink below it and consequently when describing the lower segments segment of their cirl circles esth thy will be invisible while new stars which perform their diurnal endes below the southern horizon will be brought into view view when he has arrived at the equator he will perceive cill all the stars of the fir an fn rn ament both in n the north and in in the south describe ing semicircles semi circles and remaining nearly 12 hours above the horizon orizon li when he arrives at the same distance south of the equator that we are north he will ob serve a po point int in in the heavens hea ens elevated 40 34 3 4 de deg above the southern horizon around which all the heavenly bodies in in the southern regions circulate froni from east to t west exhibiting all the phenoi phenomena nena n manifested an infested by our nori northern hern regions legions in jn this latitude this point ii is called the south pole of the heavens if he turn his eyes to the north lie he will find thit 0 our ur north pole and all the fie stars have sunk beneath the horizon hr izon and will no mole auie in in that latitude render them themselves selve s visible the stars thit that now pats pass ove over r our heads will rise nse and remain remain a few minutes above his northern horizon hon and then st set below it all the beaverly bea venly bodes bides I 1 north of the equatorial circle will present the same phenomena to him that those south ot of that circle do di to us and all the sars in in the southern hemisphere will exhibit to him the same app earan ces tint thit those in in the northern hemisphere herni sphere do to us all the heavenly bodies which WP we see set behind the west westin rn hr horizon izon will ivil pass wider the earth and rise again in the east if any one will have pa inight tience to watch h tire stars during a long winter s night lie he will in in the morning behold the sa same ne stars rs rising n iti in the east baat which lie saw early in in the even ing ins setting in in the west and thus the upper and aind lower liwer hemispheres of the heavens will be gradually grad nilly a and 1 d successively to his view new the llie precise time t nen in which h every stir stat performs its applit apparent nt d ur n nal 1 revl revolution i ion around the earth is is 23 hours hour 56 inn airs and 4 second this is is called a sidereal day and is is 3 nun min and 56 see sec shorter than a wean mean olar atour earth seems to be at test rest while the starry sphere appears to move around us from froin east eatto to west pst but if we w e suppose the stars to be at rest and the earth to rotate upon an axis axis atoni pom west to east all a 1 I 1 the phenomena above described de will take place pi ice in in the same order and in in the spine time these phenomena therefore when considered alone alne do not determine whether it is is our flur glube globe or the starry a sphere phere that is is in in rotation one or the other it it must a be th the e grind object which the almighty had in m view in producing P cing these diurnal movements rn ve ments was the alternate succession succession of day and night this ap important end could be obtained by b a simple rotation t of the earth upon js axis axis instead of causing thi the sun and innumerably nr other worlds to rev lev ive around it the planet jupiter A piter though fourteen hundred times larger than the earth moves round its own axis axis in in a little less than ten hours saturn 1 is is nearly A thousand ti times larger than the earth yet it turns on its own axis axis once in in ten hours and a half the inhabitants upon the surfaces of these planets I 1 will see the starry heavens apparently revolving around them thein in in a different position and with more I 1 than twice the velocity haf that they appear to have I 1 round the surface of our earth if not informed to the contrary they might suppose that the motion 0 of f the sun and stars around their axes was real w cereas we know ow from observation that the a jioji ion of day dav and night upon those planets is is pr due I 1 I 1 ed by their own rotations if then day and night upon other planets is is caused by their th ir own rotation I 1 why rhy may not our day and night be occasioned in in the sain same e manner mannera Is 19 it reas reasonable gable to fo suppose that our globe is is an exception to the general law lavi of roth rotation tion which we ve know obtains in in many of the other plin pl pi in ets etsa inthe magnitude of our globe be an objection to its rotation then theja the magnitudes of jupiter and saturn which are a thousand times larger would be a far greater objection to their mo motions t ions if any 0 one ne suppose that the earth must not move because of its magnitude let him turn his attention to the sun which is is more than 1390 times larger than the earth and yet it turns round upon its m a axis I 1 in in about 26 of our days moreover if the earth has no diurnal motion that thea vast luminary must fly around us every 24 hours bours performing a revolution of s every day and all tins this merely to accor accommodate the in in y leaf I 1 3 of 9 nar latif gw t roii A amt 3 11 g of f daiy diy and night no wisdom would bedi be displayed 1 d in in such an arrangement of things thing when we at stand a nd before a fire and wish to warm different sides olour of ourselves a how shall we accomplish it ita it can be done I 1 i in in two ways by attaching a piece of machinery to I 1 the chimney and moving the fire place fire and ana all 1 i I 1 around us we may be equally and alternately warrn warm J I 1 bedon ed on different sides but liow much more simple would ou I 1 4 1 it be to merely tu tuan T rn round oui ou i selves a and nd let d theah I 1 the i amney and fireplace fire place remain stationary 1 the rotation of the earth therefore in in order to experience the benefits odthe of the heat and light of the sun on its different si sides des is is infinitely infinitely y more simple I 1 an andai d C I 1 displays d splay s infinite ore or wisdom than to ZAH I 1 ody ai W I 1 now 0 I 1 v I 1 dy around il it I 1 pre presumptive eu in P t i e ainest the ad apparent diurnal eavens being 4 real is is that the sun moon aind a ve nearly the I 1 a same ame period of revolution thong 11 are bodies of dil different lerent magnitudes and a are re pl 0 a apt different distances the suzi sun is is times oin us ua than khan the moon saturn is is about 9 c jimh ti TOpS i suns d distance stance from u the planet H herschel I 1 i auble the d stance af f saturn sal urn the planet ne is more than a thousand million of miles bed d herchel henschel her chel the nearest nea reet fixed stars are times time s I 1 further fui her off than neptune and many of the telescopic stars must be at least 1000 times more distant I 1 I 1 I 1 than those seen with alie then naked aked eve the most of these bodies and probably all differ not only in ui I 1 their distances but in in their magnitudes now how is is it possible for us 0 Q conceive all these bodies to I 1 revolve around 0 our u r globe in in the short period of 24 hours hoursh why should they chev all have h ve about the same period wb when n they differ so sa m im densely in in their dist ancess why should the sun travel times fast aster ilian ihan the mona wh sh bh uld th the planet neptune I 1 t aap SO 30 times faster than the sun suna or why sh uld the nearest ri a rent fixed stai fly tidies swifter 1 than neptune can ws we for a moment believe that therease there are bodies in in the universe I 1 that fly I 1 I 1 I 1 I 1 P I 1 I 1 jewes swifter than igla all thew thene velocities must e epst if I 1 f we admit the 1 at diurnal motions of the stars to be realo real ml o these r gullie if wt apt carry with them thein agirre an irrean gible e conviction that the diurnal we tion must to the earth and net to the I 1 y 11 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