Page images
PDF
EPUB

8. TO FIND THE DIAMETER OF THE SUN.—(1.) A very simple method is to hold up a circular piece of paper before the eye at such a distance as exactly to hide the entire disk of the sun. Then we have the proportion, As dist. of paper disk : dist. of sun's disk :: diam. of paper d. : diam. sun's d.

(2.) The apparent diameter of the sun, as seen from the earth, is about 32': the apparent diameter of the earth, as seen from the sun, is twice the solar parallax, or 17.88". Thence, the Ap. diam. of earth : ap. diam. of sun :: real diam. of earth : real diam. of san.

(3.) Knowing the apparent diameter of the sun, and its distance from the earth, the real diameter is found by Trigonometry. In figure 95, let S represent the earth, AB the radius of the sun, and ASB half the apparent diameter of the sun. We shall then have the proportion,

AS : AB :: radius : sin. 16' (half mean diam. of sun). By a similar method the diameters of the planets are obtained.

APPENDIX.

TABLE ILLUSTRATING KEPLER'S THIRD LAW. (CHAMBERS.)

In the first column are the relative distances of the planets from the sun; in the second, the periodic times of the planets; and in the third, the squares of the periodic times divided by the cubes of the mean distances. The decimal points are omitted in the third column for convenience of comparison. The want of exact uniformity is doubtless due to errors in the observations.

[blocks in formation]

Arago, speaking of Kepler's Laws, says: “ These interesting laws, tested for every planet, have been found so perfectly exact, that we do not hesitate to infer the distances of the planete from the sun from the duration of their sidereal periods, and it is obvious that this method possesses considerable advantages in point of exactness.'

· MEASUREMENTS OF THE EARTH'S DIAMETER.

Airy.

Bessel.

Polar diameter........
Equatorial diameter ............
Compression .....

7899.17
7925.61

26.47

7899.11
77925.60

26.49

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

ELEMENTS OF THE SOLAR SYSTEM(continued.)

Light and heat of the sun. Earth as 1

Inclination of

axis to the plane of

ecliptic.

Force of
Gravity.
Earth as 1

Velocity in
orbit. Miles
per hou

Mass (in tons).

Mean apparent di.

ameter fm earth.

Volume.
Earth as 1.

Inclination of

orbit to the ecliptic.

[blocks in formation]

23

1.91

.851

323 29

Moon....! 27 7 433

h. m. s.
Mercury..
Venus ... slight.
Earth.... 759
Mars..... 24 37 23
Jupiter .. 1059 55 21
Saturn ... 188 10 2

41.

66° 32

1,910,278,070,000,000,000,000,000,000 32 34 1,215,126,361

78,000,000,000,000,000,000 31' 261 .020345° 8' 40"
393,000,000,000,000,000,000 8.7" .052 7° 0 5"
4,763,000,000,000,000,000,000 38.14
6,069,000,000,000,000,000,000

1.
750,000,000,000,000,000,000 17.31 .239
1,825,900,000,000,000,000,000,000 40.7" 1387.431
546,406,000,000,000,000,000,000 17.5" 1746.898 2° 29 36"
76,721,000,000,000,000,000,000

72.359

46 2819 191,720,000,000,000,000,000,000 2.8" 18.664 1• 16 69

2,273
105,330
77,050
*65,533
53,090
28,744
21,221
14,963
11,958

1° 51'

01° 18'
86° 53

6"

2.42

[blocks in formation]

NAME.

Polar

compres'n.

Axial rotation.

Sun......

Uranus...

Neptnne.

.79

« PreviousContinue »