Home » Archimedes archive » Zipped Apps » Orrery » !Solar/Describe/Moon
!Solar/Describe/Moon
This website contains an archive of files for the Acorn Electron, BBC Micro, Acorn Archimedes, Commodore 16 and Commodore 64 computers, which Dominic Ford has rescued from his private collection of floppy disks and cassettes.
Some of these files were originally commercial releases in the 1980s and 1990s, but they are now widely available online. I assume that copyright over them is no longer being asserted. If you own the copyright and would like files to be removed, please contact me.
| Tape/disk: | Home » Archimedes archive » Zipped Apps » Orrery |
| Filename: | !Solar/Describe/Moon |
| Read OK: | ✔ |
| File size: | 05DC bytes |
| Load address: | 0000 |
| Exec address: | 0000 |
File contents
The Moon is the Earth's sole companion, orbiting at an average distance of 384,400km. It follows us on our path around the Sun, making one orbit of us (as seen against the background of stars) every 27 days, 7 hours, 43 minutes. This period is referred to as the sidereal month. The Moons equatorial diameter measures 3,476km making it less than one third the diameter of the Earth. As the orbital plane of the Moon lies within 5 degrees of the apparent orbit of the Sun as seen from Earth, occasionally their positions in the sky coincide, giving rise to a solar eclipse. At other times the Moons orbit takes it into the shadow cast by the Earth into space, causing a lunar eclipse. Unlike solar eclipses, Lunar eclipses are readily observed from large areas of the Earths surface, due to the greater extent of the Earths shadow than that of the Moons. As we see the Moon only in reflected light, it shows distinct phases, depending on the angle made between itself, the Sun and the Earth. At New Moon, all three bodies are aligned, with the Moon between the Earth and the Sun. During this phase, despite the absence of direct illumination by the Sun, the lunar surface is just visible in light reflected from the Earth. Full Moon occurs when the Earth lies directly between the Sun and the Moon, with first and last quarters occurring at the 90 and 270 degree positions. The time taken from New Moon to New Moon, called the synodic month, is 29 days, 12 hours, 44 minutes.
00000000 54 68 65 20 4d 6f 6f 6e 20 69 73 20 74 68 65 20 |The Moon is the | 00000010 45 61 72 74 68 27 73 20 73 6f 6c 65 20 63 6f 6d |Earth's sole com| 00000020 70 61 6e 69 6f 6e 2c 20 6f 72 62 69 74 69 6e 67 |panion, orbiting| 00000030 20 61 74 20 61 6e 20 61 76 65 72 61 67 65 20 0a | at an average .| 00000040 64 69 73 74 61 6e 63 65 20 6f 66 20 33 38 34 2c |distance of 384,| 00000050 34 30 30 6b 6d 2e 20 49 74 20 66 6f 6c 6c 6f 77 |400km. It follow| 00000060 73 20 75 73 20 6f 6e 20 6f 75 72 20 70 61 74 68 |s us on our path| 00000070 20 61 72 6f 75 6e 64 20 74 68 65 20 0a 53 75 6e | around the .Sun| 00000080 2c 20 6d 61 6b 69 6e 67 20 6f 6e 65 20 6f 72 62 |, making one orb| 00000090 69 74 20 6f 66 20 75 73 20 28 61 73 20 73 65 65 |it of us (as see| 000000a0 6e 20 61 67 61 69 6e 73 74 20 74 68 65 20 62 61 |n against the ba| 000000b0 63 6b 67 72 6f 75 6e 64 20 6f 66 20 0a 73 74 61 |ckground of .sta| 000000c0 72 73 29 20 65 76 65 72 79 20 32 37 20 64 61 79 |rs) every 27 day| 000000d0 73 2c 20 37 20 68 6f 75 72 73 2c 20 34 33 20 6d |s, 7 hours, 43 m| 000000e0 69 6e 75 74 65 73 2e 20 54 68 69 73 20 70 65 72 |inutes. This per| 000000f0 69 6f 64 20 69 73 20 0a 72 65 66 65 72 72 65 64 |iod is .referred| 00000100 20 74 6f 20 61 73 20 74 68 65 20 73 69 64 65 72 | to as the sider| 00000110 65 61 6c 20 6d 6f 6e 74 68 2e 20 54 68 65 20 4d |eal month. The M| 00000120 6f 6f 6e 73 20 65 71 75 61 74 6f 72 69 61 6c 20 |oons equatorial | 00000130 0a 64 69 61 6d 65 74 65 72 20 6d 65 61 73 75 72 |.diameter measur| 00000140 65 73 20 33 2c 34 37 36 6b 6d 20 6d 61 6b 69 6e |es 3,476km makin| 00000150 67 20 69 74 20 6c 65 73 73 20 74 68 61 6e 20 6f |g it less than o| 00000160 6e 65 20 74 68 69 72 64 20 74 68 65 20 0a 64 69 |ne third the .di| 00000170 61 6d 65 74 65 72 20 6f 66 20 74 68 65 20 45 61 |ameter of the Ea| 00000180 72 74 68 2e 0a 0a 41 73 20 74 68 65 20 6f 72 62 |rth...As the orb| 00000190 69 74 61 6c 20 70 6c 61 6e 65 20 6f 66 20 74 68 |ital plane of th| 000001a0 65 20 4d 6f 6f 6e 20 6c 69 65 73 20 77 69 74 68 |e Moon lies with| 000001b0 69 6e 20 35 20 64 65 67 72 65 65 73 20 6f 66 20 |in 5 degrees of | 000001c0 74 68 65 20 0a 61 70 70 61 72 65 6e 74 20 6f 72 |the .apparent or| 000001d0 62 69 74 20 6f 66 20 74 68 65 20 53 75 6e 20 61 |bit of the Sun a| 000001e0 73 20 73 65 65 6e 20 66 72 6f 6d 20 45 61 72 74 |s seen from Eart| 000001f0 68 2c 20 6f 63 63 61 73 69 6f 6e 61 6c 6c 79 20 |h, occasionally | 00000200 0a 74 68 65 69 72 20 70 6f 73 69 74 69 6f 6e 73 |.their positions| 00000210 20 69 6e 20 74 68 65 20 73 6b 79 20 63 6f 69 6e | in the sky coin| 00000220 63 69 64 65 2c 20 67 69 76 69 6e 67 20 72 69 73 |cide, giving ris| 00000230 65 20 74 6f 20 61 20 73 6f 6c 61 72 20 0a 65 63 |e to a solar .ec| 00000240 6c 69 70 73 65 2e 20 41 74 20 6f 74 68 65 72 20 |lipse. At other | 00000250 74 69 6d 65 73 20 74 68 65 20 4d 6f 6f 6e 73 20 |times the Moons | 00000260 6f 72 62 69 74 20 74 61 6b 65 73 20 69 74 20 69 |orbit takes it i| 00000270 6e 74 6f 20 74 68 65 20 0a 73 68 61 64 6f 77 20 |nto the .shadow | 00000280 63 61 73 74 20 62 79 20 74 68 65 20 45 61 72 74 |cast by the Eart| 00000290 68 20 69 6e 74 6f 20 73 70 61 63 65 2c 20 63 61 |h into space, ca| 000002a0 75 73 69 6e 67 20 61 20 6c 75 6e 61 72 20 65 63 |using a lunar ec| 000002b0 6c 69 70 73 65 2e 20 0a 55 6e 6c 69 6b 65 20 73 |lipse. .Unlike s| 000002c0 6f 6c 61 72 20 65 63 6c 69 70 73 65 73 2c 20 4c |olar eclipses, L| 000002d0 75 6e 61 72 20 65 63 6c 69 70 73 65 73 20 61 72 |unar eclipses ar| 000002e0 65 20 72 65 61 64 69 6c 79 20 6f 62 73 65 72 76 |e readily observ| 000002f0 65 64 20 66 72 6f 6d 20 0a 6c 61 72 67 65 20 61 |ed from .large a| 00000300 72 65 61 73 20 6f 66 20 74 68 65 20 45 61 72 74 |reas of the Eart| 00000310 68 73 20 73 75 72 66 61 63 65 2c 20 64 75 65 20 |hs surface, due | 00000320 74 6f 20 74 68 65 20 67 72 65 61 74 65 72 20 65 |to the greater e| 00000330 78 74 65 6e 74 20 6f 66 20 0a 74 68 65 20 45 61 |xtent of .the Ea| 00000340 72 74 68 73 20 73 68 61 64 6f 77 20 74 68 61 6e |rths shadow than| 00000350 20 74 68 61 74 20 6f 66 20 74 68 65 20 4d 6f 6f | that of the Moo| 00000360 6e 73 2e 0a 0a 41 73 20 77 65 20 73 65 65 20 74 |ns...As we see t| 00000370 68 65 20 4d 6f 6f 6e 20 6f 6e 6c 79 20 69 6e 20 |he Moon only in | 00000380 72 65 66 6c 65 63 74 65 64 20 6c 69 67 68 74 2c |reflected light,| 00000390 20 69 74 20 73 68 6f 77 73 20 64 69 73 74 69 6e | it shows distin| 000003a0 63 74 20 0a 70 68 61 73 65 73 2c 20 64 65 70 65 |ct .phases, depe| 000003b0 6e 64 69 6e 67 20 6f 6e 20 74 68 65 20 61 6e 67 |nding on the ang| 000003c0 6c 65 20 6d 61 64 65 20 62 65 74 77 65 65 6e 20 |le made between | 000003d0 69 74 73 65 6c 66 2c 20 74 68 65 20 53 75 6e 20 |itself, the Sun | 000003e0 61 6e 64 20 0a 74 68 65 20 45 61 72 74 68 2e 20 |and .the Earth. | 000003f0 41 74 20 4e 65 77 20 4d 6f 6f 6e 2c 20 61 6c 6c |At New Moon, all| 00000400 20 74 68 72 65 65 20 62 6f 64 69 65 73 20 61 72 | three bodies ar| 00000410 65 20 61 6c 69 67 6e 65 64 2c 20 77 69 74 68 20 |e aligned, with | 00000420 74 68 65 20 0a 4d 6f 6f 6e 20 62 65 74 77 65 65 |the .Moon betwee| 00000430 6e 20 74 68 65 20 45 61 72 74 68 20 61 6e 64 20 |n the Earth and | 00000440 74 68 65 20 53 75 6e 2e 20 44 75 72 69 6e 67 20 |the Sun. During | 00000450 74 68 69 73 20 70 68 61 73 65 2c 20 64 65 73 70 |this phase, desp| 00000460 69 74 65 20 0a 74 68 65 20 61 62 73 65 6e 63 65 |ite .the absence| 00000470 20 6f 66 20 64 69 72 65 63 74 20 69 6c 6c 75 6d | of direct illum| 00000480 69 6e 61 74 69 6f 6e 20 62 79 20 74 68 65 20 53 |ination by the S| 00000490 75 6e 2c 20 74 68 65 20 6c 75 6e 61 72 20 0a 73 |un, the lunar .s| 000004a0 75 72 66 61 63 65 20 69 73 20 6a 75 73 74 20 76 |urface is just v| 000004b0 69 73 69 62 6c 65 20 69 6e 20 6c 69 67 68 74 20 |isible in light | 000004c0 72 65 66 6c 65 63 74 65 64 20 66 72 6f 6d 20 74 |reflected from t| 000004d0 68 65 20 45 61 72 74 68 2e 20 46 75 6c 6c 20 0a |he Earth. Full .| 000004e0 4d 6f 6f 6e 20 6f 63 63 75 72 73 20 77 68 65 6e |Moon occurs when| 000004f0 20 74 68 65 20 45 61 72 74 68 20 6c 69 65 73 20 | the Earth lies | 00000500 64 69 72 65 63 74 6c 79 20 62 65 74 77 65 65 6e |directly between| 00000510 20 74 68 65 20 53 75 6e 20 61 6e 64 20 0a 74 68 | the Sun and .th| 00000520 65 20 4d 6f 6f 6e 2c 20 77 69 74 68 20 66 69 72 |e Moon, with fir| 00000530 73 74 20 61 6e 64 20 6c 61 73 74 20 71 75 61 72 |st and last quar| 00000540 74 65 72 73 20 6f 63 63 75 72 72 69 6e 67 20 61 |ters occurring a| 00000550 74 20 74 68 65 20 39 30 20 61 6e 64 20 0a 32 37 |t the 90 and .27| 00000560 30 20 64 65 67 72 65 65 20 70 6f 73 69 74 69 6f |0 degree positio| 00000570 6e 73 2e 20 54 68 65 20 74 69 6d 65 20 74 61 6b |ns. The time tak| 00000580 65 6e 20 66 72 6f 6d 20 4e 65 77 20 4d 6f 6f 6e |en from New Moon| 00000590 20 74 6f 20 4e 65 77 20 4d 6f 6f 6e 2c 20 0a 63 | to New Moon, .c| 000005a0 61 6c 6c 65 64 20 74 68 65 20 73 79 6e 6f 64 69 |alled the synodi| 000005b0 63 20 6d 6f 6e 74 68 2c 20 69 73 20 32 39 20 64 |c month, is 29 d| 000005c0 61 79 73 2c 20 31 32 20 68 6f 75 72 73 2c 20 34 |ays, 12 hours, 4| 000005d0 34 20 6d 69 6e 75 74 65 73 2e 0a 0a |4 minutes...| 000005dc
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