Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: wex on 11/06/2007 04:46:27
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When you're in space how do you know which way is up? Is there a universally agreed upon point of reference? If you're a space ship and you encounter another space ship, would you both be in upright position because you're pointing towards the same "up" or would one ship be floating on its side or something because it's poiting to a different "up"?
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The idea of up and down for the Solar system was established by the navel powers that were predominantly in what we call the northen hemisphere there is no reason why it should the same on any other planet.
Of course the orbital plane of another system could well be at right angles to us in which case the aliens could be flying sideways
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Wex and Syphrum
Well answered Syphrum..... Only, I believe that Up is directly relative to where you are on the planet and, it would depend which planet you were aiming at...., and it would depend where the stellar system is tonight depending upon the day of the month and all that jazz [::)] However, there are certain portals in the stratosphere through which one needs to proceed. Where I live, what I would do is, move toward the portal directly above my home, or closest thereto, then I would program my ship to travel to a certain location and know that the people who built my ship have already pre-programmed my ship to know and understand the co-ordinates programmed into it via various shortcuts on my console board. So I need only press 'B' on my keyboard to program the ship to time travel to say, Betelgeuse. And, of course, my organically intelligent ship will avoid collision with any oncoming traffic. [8D]
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Even inside a spaceship in freefall - orbit - up is not a well defined direction. I believe that astronauts choose an arbitrary direction to be up in each room of the space station because it makes them feel less confused, but there is no other reason to.
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It's easy when there's no gravity - just pick an abitrary direction. However, when approaching a planet, or any other object with sufficient mass, it becomes more tricky. As you head towards the planet you see it in front of you; much as you would were you driving along a road towards something you could see in the distance. However, as the gravity starts to affect your inner ear you start to feel as if you are heading downwards towards the surface.
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Gravity will only affect your inner ear if you not falling with it.
If you are in a spaceship and not firing your rockets you will not be pushed so not feel an upwards direction. We only feel an 'up' because the ground is pushing us upwards all of the time.
If the spaceship is not firing rockets or entering the atmosphere it is in free fall, so you don't feel what we call the effects of gravity. There is almost as much gravity on the International space station as on the surface, they are just falling all the time so don't feel it.
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Dave - I meant it in the sense of approaching Earth, entering the atmosphere & then landing. What once seemed to be in front of you then becomes below you.
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Sorry
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It was a reasonable question to ask but that reply regarding 'navel' powers is ridiculous.
The points of the compass and 'magnetic-north' were understood long before any navy decided about navigation.
On a more serious point, how can you have faith in any answer from someone who obviously doesn't know the difference between 'naval' and 'navel'?
Where I come from your navel is your lower abdomen and perhaps that particular contributor should contemplate theirs more closely
get a grip
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daveshorts - if gravity is pushing you up off the ground then you're full of too much hot air because gravity holds us and the atmosphere DOWN!
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Ashtari - if you come back through your portal why don't you consider that every object with mass has a magnetic field and that all you need is a compass to show North on any planet and that is UP?
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Probably because the presence of mass does not guarantee the existence of a magnetic field, and even those bodies that have a significant magnetic component do not necessarily have a dipolar field like ours. Plus the fact that near the poles, the field direction is downwards (or upwards) towards the centre of the earth, whereas at the equator is is horizontal.
"Up" means away from the centre of the earth, or whatever planet you are standing on. It has no meaning in deep space, but there are plenty of distant reference points to choose from, so if you are approaching another space ship you can agree to orient the first latch of your docking port towards, say, Canopus, Polaris, or any other mutually recognised star. On close approach, as with docking any other vehicles from space shuttles to caravans, you agree which is to be the reference ship and rotate the other one to align with its docking guides.
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As the OP was on 11.06.07; and as Wex has just one post to his/her name, it might be reasonable to assume a degree of discontent with the answers. It may be too late to rectify that.
There’s one thing I’d like to know, though:
get a grip
On what? Your navel?
If so, and if you are in the area of your lower abdomen it may be necessary to look at the direction of "up".
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It would seem like one might have multiple definitions of up. And, in many senses it wouldn't really matter.
Up may be in the direction opposite of gravity or acceleration (down). If one had centrifugal force artificial gravity, then one might consider up as being towards the center of the ship/circle.
Perhaps one would consider up as being towards one's head. So, if one was strapped into a seat on an apollo spacecraft, sitting on the launch pad. One would in effect be laying on one's back, but up may be either the area above one's head, or the area towards the nose of the rocket. Controls may be laid out as if one was sitting upright.
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Orbital navigation can be tricky. If you are following behind another spacecraft in the same orbit and want to dock with it, our natural inclination might be to fire our rocket behind us, thinking this will push us forward towards the other spacecraft. Unfortunately, this rocket burn will drive us into a higher orbit, which orbits more slowly, and we will fall further behind!
In fact, you must fire your rocket towards the other spacecraft, which will drop you into a lower (faster) orbit, allowing you to overtake the other craft, at which point you can fire the rocket again to return to a higher orbit and rendezvous.
To find out more than you ever wanted to know about orbital navigation, listen to 1.5 hour podcast at:
http://traffic.libsyn.com/omegataupodcast/omegatau-104-spaceFlightDynamics.mp3
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First of all 'visitor', those guys are all good :) and fun to read. But the discussion was 2007 so it's a pretty old thread. And we define up and down relative gravity, not relative a compass.
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So, if one was strapped into a seat on an apollo spacecraft, sitting on the launch pad.
Your navel would indeed be up lol
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When space travel becomes the norm, all new launching ships will point there nose
at upsilon in Andromeda. then start a gyro. from then onwards that way is up.