stopping in space?

[bdewoody]

We see often in Sci-Fi movies spacecraft being stopped. I think that concept is meaningless as regards space travel. What would you be stopped relative to?. They also talk of coordinates in space but since everything is moving no object would stay at the same location. So it seems that navigation in space will require some powerful computers with a lot of memory. <div class="Discussion_UserSignature"> <em><font size="2">Bob DeWoody</font></em> </div>

 

[origin]

You are quite right you can only be stopped relative to something else. For instance the shuttle can 'park' at the space station but of course they are orbiting Earth at thousands of miles/hr.<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[CalliArcale]

Some science fiction movies/shows/books operate under the assumption that some universal coordinate system has been established for the purposes of navigation. You could do this. You can certainly have coordinates in space. They'd be arbitrary, but then, so are latitude and longitude on Earth. They're relative to some arbitrarily chosen point. I think Star Trek uses the galactic center as its reference point, for instance.<br /><br />The series Babylon 5 generally did a good job with this sort of thing. They occasionally showed objects "parked" which nevertheless moved relative to the station. <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>

 

[ashish27]

nice answer Calli!

 

[heyscottie]

Longitude certainly is arbitrary, though I would say that latitude is not.<br /><br />We could, for example, create a simple galactic coordinate system that first defines a galactic plane. The galactic center (perhaps the supermassive black hole) would need to be located on this plane. The plane would be constructed such that the standard deviation of distances of stars from the plane in the galaxy would be minimized.<br /><br />We define the origin as the supermassive black hole. We can then start defining axes. The x-axis would be the line from the origin within the plane that passes closest to the sun. (Why not?) Since the sun may not be in the plane, the axis will not pass directly through it.<br />The y-axis is the line normal to the plane passing through the origin. The positive direction could be in either direction. The z-axis is then set so that the three axes form a right-handed cartesian coordinate system.<br /><br />And there you are!<br /><br />Of course, the coordinates of all objects would be continually changing, except for the origin's. The sun would always have a zero y-coordinate, but its x and z coordinates would change.<br /><br />This is just one possible way to do it; there are many.

 

[vandivx]

is not CMB radiation sometimes taken for absolute like determination of motion - when you 'move' in such a way that it is redshifted in all directions equally you can say you are at rest to cosmic space regardless how everything else around you moves?<br /><br />than you need to make up coordinate grid with some conveniently chose origin (as explained above) so you could identify locations of other objects 'parked in absolute space' like you or to know where to go if your commander tells you to go to XYZ place<br /><br />I think one day there may exist other and perhaps more valid or reliable ways of detemining absolute rest in space but as always the origin will have to be chosen arbitrarily as per convention of particular civilization which will depend on whether they are 'merely' star going or galaxy going civilization although I can even conceive of the day when we should be able to dermine center of universe which would then be objective origin of that absolute coordinate space, the orientation of the axis would have to always be arbitrarily given as per above post unless the universe would be found to have some special shape and the axes would then be keyed to that<br /><br />in Sci-Fi movies they often seem to have means of propulsion that work on 'space propulsion' principle as opposed to matter expulsion one (which I think is called inertial principle which means ejecting matter at high speed opposite the direction you want to go), that is the flying machines seem to get their impetus for moving by pushing off space as such which at present times we can't do at all<br /><br />such civilization that could do that would have at their means absolute space determination (more reliable than coming to rest in CMBR background), as a caveat though, notice that unless there is some special utility of coming to rest in absolute space it doesn't have much appeal, in practice you always want to be at rest to something, like in respect to your house or more particularly the sof <div class="Discussion_UserSignature"> </div>