This has been confusing me

[robrob]

Bear with me on this,<br /><br />Now, this may make me look stupid I have to ask 'cos someone will know, but if you got a telescope and took it to the South Pole, then surely you'd be looking in a different direction to someone in, say, North America, and certainly somone in the North Pole, so why aren't there other planets etc North and South of the Earth, or am I just making an idiot of myself? Is the answer simply gravity, as in things can only orbit the Sun in a certain way? Or is that a stupid notion also? Is it possible to create a half man, half monkey type creature?

 

[CalliArcale]

It is correct that you see a different part of the sky from the southern hemisphere than from the north. Dramatically, the southern sky features the Magellanic Clouds, satellites of our own Milky Way galaxy. I really want to see them someday. <img src="/images/icons/wink.gif" /><br /><br />But you don't see different planets. The reason for this is that the major planets (the big ones) orbit near the plane of the Sun's equator. This means that to an observer on Earth, they seem to stay quite close to an invisible line called the "ecliptic". The ecliptic is the path the Sun follows over the course of the year. This line happens to pass through twelve constellations, and the ancients noticed this. These twelve are the zodiac.<br /><br />The ecliptic moves over the course of the year because the Earth's axis is inclined; it is not perfectly perpendicular to the plane of the ecliptic. As you probably already know, this produces the seasons, as the Sun's apparent path in the sky moves over the course of the year. The ecliptic moves with it. But it generally stays in a particular swath of sky. To northern observers, it is in the south. Tropical observes get to see it straight overhead. Southern observers see it in the north. It is visible from the entire planet at least part of the year. (Arctic and antarctic observers are the only ones who completely lose sight of it -- during the darkest days of their local winter, when the sun doesn't rise at all.) But the major populated regions always see it. Since that's where you see the planets, northern and southern observers see the same planets.<br /><br />There are some objects which do not orbit in this plane, however. Comets are notorious for their inclined orbits, for instance. These may only be visible from one hemisphere at a time. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[harmonicaman]

To expand on <b>Calli's</b> fine explanation...<br /><br />In the late 1700's, Astronomer Charles Messier compiled a useful catalogue of interesting astronomical objects which are viewable with today's small telescopes.<br /><br />Since Messier did his observations from Paris, France, (in the Northern Hemisphere), all 110 Messier Objects¹ are only viewable from the Northern Hemisphere!<br /><br />The smallest and most well known constellation in the Southern Hemisphere is the Southern Cross, or Crux.<br /><br /><br /><br />1. Notable <b>Messier List</b> objects of the Northern Hemisphere:<br /><br />M1 The Crab Nebula <br />M6 The Butterfly Cluster <br />M7 Ptolemy's Cluster <br />M8 The Lagoon Nebula <br />M11 The Wild Duck Cluster <br />M13 The Great Hercules Globular Cluster <br />M16 part of the Eagle Nebula <br />M17 The Omega, Swan, or Horseshoe Nebula <br />M20 The Triffid Nebula <br />M24 Milky Way Patch <br />M27 The Dumbell Nebula <br />M31 The Andromeda Galaxy <br />M32 Satellite galaxy of Andromeda <br />M33 The Triangulum Galaxy <br />M40 Winecke 4 <br />M42 The Great Orion Nebula <br />M43 part of the Orion Nebula, de Mairan's Nebula <br />M44 Praesepe, The Beehive Cluster <br />M45 The Pleiades <br />M51 The Whirlpool Galaxy <br />M57 The Ring Nebula <br />M63 The Sunflower Galaxy <br />M64 The Blackeye Galaxy <br />M76 The Little Dumbell, Cork, or Butterfly <br />M81 Bode's Galaxy or Bode's Nebula <br />M82 The Cigar Galaxy <br />M87 Virgo A <br />M97 The Owl Nebula <br />M101 The Pinwheel Galaxy <br />M102 The Pinwheel Galaxy <br />M104 The Sombrero Galaxy <br />M110 Satellite galaxy of Andromeda

 

[harmonicaman]

<i>"Is it possible to create a half man, half monkey type creature?"</i><br /><br />Yes! <br /><br />Well; um, sort of... <br /><br />Read the fascinating story of the very famous Piltdown Man hoax! <br />

 

[siarad]

It wasn't a hoax while I was at school but in some doubt.

 

[robrob]

"The ecliptic is the path the Sun follows over the course of the year. This line happens to pass through twelve constellations, and the ancients noticed this. These twelve are the zodiac."<br /><br />The Sun is actually moving?<br /><br />

 

[Saiph]

yes...and no.<br /><br />Yes, it is moving through the galaxy.<br /><br />Yes, it is moving relative to earth...but not much...so a sorta "no" answer.<br /><br />As far as the ecliptic goes, and the sun's "motion" it's a consequence of earth orbiting the sun.<br /><br />Find an object you can walk all the way around (preferably at about eye-level). Identify a bunch of land-marks around the object. Each major land-mark (like the couch...or the tree, or whatever) is a constellation.<br /><br />Walk around the object...and you'll see it pass in front of all those different land-marks. If you consider yourself stationary (since we don't <i>feel</i> like we're moving on earth) you could say that the object is moving along a specific path, moving in front of those land-marks.<br /><br />now, just to be perfectly accurate: Motion is relative. It's just as valid to say I'm moving, and you're not, as vice versa. That the earth is moving, the sun isn't, or vice versa. The math, the physics, and the consequences are identicle in all cases. However, some arrangements are easier to work through than others. Have a sun-centered solar system provides the easiest solutions to the issues of solar system motions (and jives best with gravity of course), but it isn't the "only" way to solve the problems (and not even the most accurate! though it's very good). <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

 

[CalliArcale]

It's easy to see the apparent motion of the planets or moon against the backdrop of stars. One night you see Jupiter in the constellation of Leo. Some time later, you see it in Cancer. This is because of the relative motion between the Earth and Jupiter, of course. It makes more sense if you picture the "celestial sphere", an imaginary sphere on which all of the "fixed" stars are painted. The Sun is at the center of that sphere, and the planets all orbit well within the sphere. Obviously, it's not real, but the "fixed" stars are so distant it take sensitive equipment to detect that they are not actually fixed to a huge sphere but are scattered at vast distances; for most purposes, they're far enough away that the actual distance is unimportant.<br /><br />Noticing the Sun's motion against the backdrop of the celestial sphere is harder, becuase of course its brillance washes out all the stars. Total eclipses are too rare to really be useful for this. But there are a couple of ways to detect it. The celestial sphere appears to rise and set along with everything else, taking one day to go around. (Actually, it takes slightly longer than one day -- a period called a sidereal day. A calendar day is the length of time it takes the Sun to make one apparent circuit around the Earth. A sidereal day is the length of time it takes a fixed star to do the same thing. The fact that these are not identical is due to the fact that the Earth orbits the Sun.)<br /><br />The way the ancients worked out the Sun's position against the celestial sphere was by observing the heliacal rising of various constellations. This is when the constellation rises just before the Sun does. Essentially, they used the limb of the Earth to mask the Sun so they could see what constellation it was in. Many ancient people's ascribed predictive properties to this event. To some extent this was useful; they realized that the pattern of constellations repeated on a regular cycle of 365 days -- on <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[CalliArcale]

I'd forgotten about that. Thank you. <img src="/images/icons/wink.gif" /><br /><br />My hunch is that 12 was adopted because 12 is approximately the number of lunar cycles in a year. Many ancient calendars, especially the Middle Eastern ones from which modern astrology largely derives, are based on lunar months, not percentages of the year. This is why the dates of various holy days vary from year to year. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>