ASTRONOMICAL NOTES FOR AUGUST.

Wairarapa Age, Volume XXXII, Issue 9559, 4 August 1909, Page 3

ASTRONOMICAL NOTES FOR AUGUST.

*"(sv the Rev. K W. Fairclough, F.K.A.S.) Venus and Jupiter are now evening stars, low in the west. Jupiter ia sinking behind the sun and Venus is rising from behind hi in, and is highsr every night. The two planets will be very close together on the 12th. Mara rises about half-past nine o'clock, and will be close to the moon on the 9th. Saturn rises about an hour after Mars. Venus and Mercury present all the phases of thi moon as they change their positions in relation to the sun. When Venus is at her brightest she is but a thin crescent form with the naked eye; certainly it can be seen with a pair of field glasses, but she is so bright that a thinly smoked glass should be used to take off the glitter. Many good observers claim to have seen the dark part of Venus, like the "old moon in the new moon's arms." It is an unsolved problem where the illumination come from that makes the dark side visible. In the case of the moon it is "earth shine"; but earth shine on Venus, though it far exceeds that of any star or planet in our skies, as quite insufficient to cause this spectral illumination. Some have suggested that there is a phosphorescence in the planets'atmosphere; others that the light is auroral; other suggest phosphorescent oceans; and others a glowing hot surface; others again suggest visibility by contrast; and yet others that it is owing to the projection of the planet into a bright background, such as the Zjdiacil Light. Whilst there are so many theories in the field, none of them can be wholly satisfactory. It, i 3 not yet certain whether Vtnus, rotates on her axis, like the earth, in a few hours, or whether she turns one face constantly to the sun. Several great observers contend for the latter opinion, but sume recent spectroscopic observations seem to favour the short period of rotation Until this question of rotation is settled probably ihe occasional luminosity of the night side of Venus will not be satisfactorily settled. If ' she turns one face constantly to the sun, the hemisphere that is in perpetual night will probably be enduring an endless ice age. If the dark fcide is a covered with snow, that may be an element in the solution. Meantime M. Hansky finds that tha dark side is more visiblte during maximum periods of solar acti ity than at others, and ha adopts tha theory of Arrhenius, referred to la3t month, that the radiation pressure of the sun bombards space with electrified ions, especially at maximum sun spot period?. These, he thinks, cause our Auroras, and Hansky says they muke the atmosphere of Venus phosphorescent

|ln 1896 an American astonomer, Guthman, saw a meteor crossing the face ot the sun. The transit occupied eight seconds. In the same year another observer saw an object cross the full moon in three or four seconds. The body was one-thir-tieth of the moon in diameter. Both of these objects roust hav<? been very large meteors, far beyond the earth's atmosphere. These observations majr shed light on the curious "Coon Mountain" in Central Arizona. The hill is circular and from 130 to 1(50 feet high. In its centre there is a "crater," nearly circular, ar,d three-quarters of a mils in diaineter. The "crater" is from 530 to 560 feet deep, and therelore 400 ft below the plain; Mr Baringer, a geologist, having examined the formation, is qute confident that it was caused by "thy impact of a large meteoiite, or sm ii asteroid." Mr Tilghmann, a physicist, says that he "is justified under due reserve as to subsequently developed facls, in announcing that the formation is due to the impact of a meteor of enormous and unprecedented size." Cedar trees 700 years old are growing on the hills. Mr Gilbert, reasoning from artillery experiments, thinks »that it would not be impossille for such a large body, plungir.g straight down, lo reach the earth with a velocity sufficient to produce this crater. The sides of the crater are of sedimentary rocks, and they have been shattered as if by some external force. Many borings, one of them 842 feet deep, have been made to find the msteori f e, but without success. It is suggested that tha heat developed by the impact dissipated the mighty bolt from the blue. That, however, seems improbable. It is a curious fact, however, that a very large iron n.eteruite was found in the Canyon Diabolo, two and a half miles away, a.id that numerous lesser ma scs lie in the neighbourhood. The?e are thought to be fragments of the great missing meteor. Thj investigatoi-s seem quite satisfied, according to Smithsonian Institute reports, that the "crater" is not of volcanic origin.

Tnis suggests "impact," and Dr. Svante Arrheniua's bcok on " Worlds in the Making." His pet subject is, "Radiation Pressure." The existence of such a pressure has been proved, by experiment. A particle 0.0015 millimetre in diarnster would be balanced against solar gravitation. Smaller particles would be swept away, ihat is, if they reflected all the light that impinged upon them. But the particles must not be too small. They must be in circumference more than 0.30 of the wave length of the ray ox light thrusting them, or the light will miss its hold. The pressure is at is maximum when the of the particle equals the wave length. It will then be forty times as great as gravity. o,ie cubic centimeter of water contains 470 billions of such particles, and earh such particle contains 96 million molecules. Ihe particles capable of being excelled are therefore similar in magnitude to the smallest specimens organic germs revealed by the microscope. Gasses escape repulsion, their molecule being much too small. But gases become conductors of electricity by being "ionised," i.e., played upon by cathode and ultral .

violet rays, or by great heat. lone ised molecules of gas adhere to theparticules of solar dust, and hence tbey become charged with negative and positive electricity. Negative ions condense vapour of water more readiy than positive ions. Hence the negative and positive particles fail apart and electric discharges takes place between them. This produces the luminosity of comets' tails, the corona and Zodiacal Light* The light pressure sifts the particles according to size and reflecting power, and so produces tails of different degrees o± curvature in a comet. Great sunspots have their maximum magnetic effect on the earth 45 hours after they pass the solar meridian —that is 45 hours after the earth gets into the direct line of fire. Arrhenius supposes that the electrically charged articles reach us from the sun in that time, which involves a velocity of 910 kilometres per second (a kilometre is about 1,100 vards.) The sun probably loses 300,000 million tons of "dust" in a year, and may gain as much from trie fall of Perhaps 200 tons of this solar dust >reaches the earth in a year, it is attracted to the magnetic poles of the earth, and by its inter-discharges causes the auroras. All the stars are sowing tis light driven dust through space, and space I therefore contains unthinkable stores of it. It dims the distant stars; it falls on all' bodies, but is especially caught by the vast nebulae, and these shine by the discharge of electrical particles arriving from ail directions. These intruding particles probably become centres of conpensation in the nebulae. They also condense and cohere in space and form me ;eors, and, being no longer subject to effective light pressure, return to the sun. Comets are probably composed of this dust and, for that reason, this substance is especially liable to be blown away again in tails, by the gales of lieht. We cannot follow Arrhenius through all the marvels of worldbuilding performed by his "dust," but we have said enough to show that he spurs his hobby hard. He even thinks that organic germs of life floating high in the atmosphere may be caught in the solar wind and carrieJ to other w)rds. Ha calculates the time the germs would he exposed to the absolute zero of cold before they arrived at this and the other planet and etar! It is said that wireless messages are three times as effective at night as by day A follower of Arrhenius supposes that the arrival of charged dust from the sun curing the day hamstrings the messages, while the night side of the world is shielded from attack.