How do direction work in space because north,east,west and south are bonded to earth? How does a spacecraft guide itself in the unending space?
In: Physics
When away from the earth, stars serve as a suitable reference point. The north star is still in the same direction, even in space, and other stars become easier to use because you are no longer on the surface of a rotating sphere. Essentially, in space every star can be the north star.
[removed]
[removed]
Currently we map objects in the sky using polar coordinates. Two angles and a distance.
Usually we use Earth as the centre point (in fact the viewers position on earth) and we work out the angle the object is from the centre line of the sky (that we define) and then the angle off the horizon.
This is declination and right ascension.
It doesn’t make much sense for an interstellar space ship to use earth as the centre point. So we might use the centre of the galaxy. Then define 0 degrees as the line through the sun.
So the solar system would be at 0°,0°,25kly
Changing direction would also likely use angles. Similar to how boats do it. Change angle a by x° and angle b by y°.
I don’t know how actual space craft do it but there it’s precedent in fiction with star trek. At the end of an episode the captain might command the helm to set a course 120 mark 43. That’s your two angles relative to something (the ship, the galactic plane or something)
Ooh, I know this one. It’s called a [gimbal](https://en.m.wikipedia.org/wiki/Gimbal). The concept is used in [inertial navigation sysyems](https://en.m.wikipedia.org/wiki/Inertial_navigation_system). Basically, 3 gimbals provide your 3D reference (xyz) to orient yourself. The gimbals will always be spinning in the exact same orientation in space no matter how a spaceship flips and spins. There’s a scene in apollo 13 where they talk about [gimbal lock](https://en.m.wikipedia.org/wiki/Gimbal_lock), meaning they’re losing their ability to orient themselves because one of the gimbals is close to being “trapped” or “caught up” with another gimbal, losing orientation in that axis. [Here’s](https://youtu.be/OmCzZ-D8Wdk) a short video explaining it.
Edit: ~~Imagine two of the gimbals represent the xy-plane and its parallel with the Earth’s orbital plane around the sun. You can read the gimbals to tell you if you’re pointing “above” Earth’s plane of orbit or “below” Earth’s plane of orbit (assuming the North pole points “up” for us northern hemisphere dwellers).~~ I’m guessing, I shouldn’t do that.
More science related to gyroscopes and the relevant phenomenon with demonstrations you can see [here](https://youtu.be/XPUuF_dECVI?t=23m). See also 35:35 for another demo.
Edit: Silly me. Walter Lewin specifically talks about it in this video at 43:50. Watch that.
Edit: I’m an idiot. I’m talking about the gimbals like they’re spinning. They’re just the rings free to rotate and allow the central gyroscope to spin and maintain its initial position. Don’t trust everything anyone says.
Directions only work with a reference point (even on earth – the reference point could be the geographic or magnetic poles)
So in space, a traveller would need reference points – possibly using the center of the galaxy or distant galaxies as reference points. Of course it wouldn’t be called N, S, E, W because there are 6 “cardinal directions”.
For travel within the solar system, the sun would be a reasonable reference point perhaps along with a few distant stars.
Just like on earth n,w,e,s are meaningless without a reference. The same will apply to space.
Since things move in space you will need to use coordinates relative to some set objects. Say certain stars. We havent really begun space exploration to really hammer out a good system but we do use angles and distance that are relative to earth.
A space force is more similar to the navy than the air force. Don’t think of a spacecraft like a jet plane; think of it like a submarine – they travel in relation to themselves as the reference plane (down angle, port, etc) and less in relation to nsew coordinates.
Hi y’all,
This topic is very complex and certainly need simplifying. That is the goal of the sub. Something that confuses some is that the target audience is ‘lay-person’ and not a literal five-year-old. ^(shout-out to r/ELIactually5, which gets no love)
So as mods we have a really interesting problem. What do lay people understand? What words are known to the average joe on the street. ^(As reddit mods we are, of course, of the upper reaches of the intelligence spectrum)[.](https://youtu.be/wyyr3L3rFvA?t=10)
So we have to assume that x-thousand upvotes (and only a few reports) means it was digestible to most.
Feel free to use the reports or comment in the sub in my footer if you want to discuss the rules. I’ll even link it here in the sticky.
[Here’s a link to the rules](https://www.reddit.com/r/explainlikeimfive/wiki/detailed_rules), which have recently been rewritten to be more informative/clear.
—
As always, I am not the final authority on any of this. If you want my mod-action reviewed you can [send a modmail](https://www.reddit.com/message/compose?to=%2Fr%2Fexplainlikeimfive). If you want to have a meta-conversation about the rules of the sub you can make a post in r/ideasforeli5 which is our home for that.
—
If you want **even more words** look at the reply below. ^(users love more words, always)
Easy, the enemy’s gate is “down”. I’m not a space engineer of any sort, but I can at least talk about the math that’s helpful here (linear algebra).
When you are walking around, you can talk about how things are *in front/behind* of you, *to the (right/left) side* of you, or *above/below* you. If you want to be clever, you can mix the descriptions too: “enemy ship at 2 o’clock!” means something is mostly to your right, but also a bit in front of you.
When you’re talking to someone else that isn’t facing the same direction, you can’t just use the forward/right descriptions anymore, so you have to pick something both of you understand. A nice one is to align to the Earth with North/East/South/West. Or, if you know what direction they’re facing, you may choose to use their perspective instead (“turn right on Maple, then turn left on Jefferson…”).
To give directions, you only need to define the three basic directions “up”, “right”, and “forward” and go from there. The third can be derived from the first two, so really you just need two of them. Usually you use some sort of reference point(s), maybe a star or a planet or your own spaceship, whatever.
ELI25 note: a set of *n* directions for an n-dimensional coordinate space is called a *basis* space, and requires *n* orthogonal vectors. Converting from one basis to another is very easy with linear algebra. With as few as three points that aren’t all on the same line (e.g., center of the sun, North Pole of the sun, some other star) you can create a full basis because of the neat property that the cross product of two vectors is always orthogonal to both input vectors.
Latest Answers