Direction

[chobochan]

This might a stupid question but exactly how do you tell direction in space?<br /><br /> I've always kinda wondered that. ^_^

 

[harmonicaman]

The answer to this question is really a lot simpler than you might expect. Every point in the universe shares these common relative perspectives as to their "Place" in the universe:<br /><br /><i>Every point in the universe sees themselves as the oldest point in the universe.<br /><br />Every point sees themselves as the most centralized location in the universe.<br /><br />Every point sees themselves as being located the farthest distance from the universe's beginning.</i><br /><br /><b>So the answer is:</b> <i>In space, any direction takes you right back where you started!</i><br /><br /><big><b>E=mc²</b></big><br /><br />

 

[drwayne]

Is you question a cosmological or a naigational question?<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[doubletruncation]

If your question is a navigational one, you can use the stars to figure out which direction you're pointing. First of all, assuming you're not too far from the Sun, the Milky Way forms a band around the sky with a bright dust filled bulge of stars on one location of the band. So you can identify any direction in space with two unique coordinates - the angle above or below the band, and the angle around the band. If you're close to the Sun you can look for patterns amongst the brightest stars in the sky. For example, the constellation Orion also lies in a specific direction in space. People use this method of finding directions and positions on the Earth as well (e.g. out at sea). Some of these stars are actually closer to us than others so if you were to move away from the Sun in some direction the closest stars in the direction you're moving would appear to shift position with respect to the farther stars (think about driving towards some hills that are in front of very distant mountains, as you aproach the hills their positions with respect to the mountains will appear to change), so by knowing how the stars look from the Sun, you could infer how far you've moved from the Sun and in what direction you've moved by seeing how the patterns of stars have changed. Of course, there's a limit to how far you can go and still use this method, it probably wouldn't be easy to do it this way if you left the galaxy for example. The stars actually do appear to move slightly with respect to each other, so after thousands of years the patterns of stars will look noticeably different. If you chose something much farther away, like quasars, they're so far away that they don't move detectably at all so you can define a very stable set of directions on the sky using them. In fact, using quasars to define fixed directions on the sky, people have been able to measure things like continental drift on the Earth (see for example: http://www.ast.cam.ac.uk/~ips</safety_wrapper <div class="Discussion_UserSignature"> </div>

 

[vogon13]

Might be a religious inquiry . . . . . <br /><br />What moral precepts will guide you when you're alone, in the cosmic dark?<br /><br /><br /><br />( <img src="/images/icons/smile.gif" /> )<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[doubletruncation]

<blockquote><font class="small">In reply to:</font><hr /><p>So the answer is: In space, any direction takes you right back where you started!<p><hr /></p></p></blockquote><br /><br />Just to qualify this statement - this is true when you talk about huge scales larger than 100s of millions of light years (Andromeda is about 2 million light years away). If you were to average the density of the universe on a 100 million light year scale, then one point would be the same as another. Thankfully, on scales smaller than this the universe is not uniform. There is a big difference between being in a void or being in a galaxy supercluster, between being in a galaxy and not being in a galaxy, between being near a star and being in interstellar space, and between being on a planet and floating around in interplanetary space. <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

Direction in the literal sense is a human concept based on the observers perspective. Cosmologically speaking, direction is: "That way forward through spacetime". <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>