How do we decide which way is "North" on other planets?

[mmntech]

We do? I'm pretty sure we use magnetic north given that every traditional compass says so. Cartographers fixated on magnetic north because it hasn't changed during humanity's written lifespan.

This thread also makes me ask the question - in space, which way is "up"?

Modern navigational instruments use rotational north. The reason being that the magnetic north pole tends to drift around. It's not as accurate.

 

[z1ggy]

Yep, because tomorrow all our compasses are just going to point the wrong way, just like that!!!!

Besides, I was trying to be humorous and point the fact out that 'we' probably won't be around because we will have killed each other off before we see it flip.

 

[vailr]

Alright. Suppose there is a huge, round rock floating in space. It has no magnetic field. It is not part of a planetary system (no star). You can't even really tell if it's rotating. Which way is north? How do you even start to draw a map?

Just arbitrarily pick a prominent feature, and assign that as "ground zero": zero degrees latitude & longitude. Pick another feature, and draw a line between the two features, and extend that line circling around the object's center of mass. Call that line the equator line, or zero longitude line, whichever. And go from there.
But if you're not planning on landing on it and digging minerals or something, just take some photos and don't bother with what direction north is.
There are some planets (such as the planet Uranus) that somehow got knocked on it's side, so that the line between the 2 rotational poles are at nearly the same angle as the (relatively flat) plane of the solar system. Uranus has no solid features, so knowing which direction is "north" wouldn't really be of much practical use, anyway.
Venus is another planetary oddity, in that one Venusian day is longer than a Venusian year.

 

[mmntech]

Yep, because tomorrow all our compasses are just going to point the wrong way, just like that!!!!

It does matter when you're doing precision navigation over long distances. This is called declination. It can be a big issue if charts are out of date or don't account for it. GPS uses true (rotational) north. True north never moves so it gives you a consistent reference point for navigation.
http://adventure.howstuffworks.com/outdoor-activities/hiking/compass-or-gps2.htm

 

[SunnyD]

Modern navigational instruments use rotational north. The reason being that the magnetic north pole tends to drift around. It's not as accurate.

Modern navigational instruments use "GPS North", which can be wildly inaccurate depending on whether your drone happens to be flying over Iran or not.

 

[Ichinisan]

Why would we waste our time with it, to the point we need factual references for North?
For simple mapping, recon, and possibly mining operations, they could just as easily make an arbitrary North and agree that all maps and operations will reference that orientation.

Then how do you, looking at the map and looking at the object, find the point of reference on that object?

Thought experiment:

Imagine the object...

1. Is not part of a planetary system. No star.
2. Has no magnetic field.
3. Has no distinguishing features aside from marks that are all equidistant from each other.
4. Has no discernable rotation.

"Meet the pioneer miners at location X." -- Where?

 

[Ichinisan]

If it's not rotating, the rock probably isn't round.

Anyway, since you're the first person on the non-rotating rock you get to pound a stake and declare the spot to be the 0, 0 point, pace off ten meters, pound another stake, scrawl an N on it, and start mapping. For longitude, it worked for the folks at Greenwich.

Round or not...it's an object to be mapped.

OK. I have a map. How do I program a blind computer-guided probe to find the stake at point 0?

 

[Ichinisan]

Modern navigational instruments use "GPS North", which can be wildly inaccurate depending on whether your drone happens to be flying over Iran or not.

I wonder how many people understand the Iran reference :hmm:

 

[mmntech]

Modern navigational instruments use "GPS North", which can be wildly inaccurate depending on whether your drone happens to be flying over Iran or not.

That's what happens when you have lack of military intelligence. :sneaky:

 

[randay]

Alright. Suppose there is a huge, round rock floating in space. It has no magnetic field. It is not part of a planetary system (no star). You can't even really tell if it's rotating. Which way is north? How do you even start to draw a map?

I suggest using landmarks.

 

[randay]

Modern navigational instruments use "GPS North", which can be wildly inaccurate depending on whether your drone happens to be flying over Iran or not.

there is no such thing as gps north. not sure if you are being facetious for the sake of your joke or not, if so disregard.

 

[vailr]

Round or not...it's an object to be mapped.

OK. I have a map. How do I program a blind computer-guided probe to find the stake at point 0?

Use a probe that isn't "blind": put a GoPro HD camera on the probe. If necessary, use a paint ball gun loaded with white paint to mark the spot.

 

[SunnyD]

I wonder how many people understand the Iran reference :hmm:

Obviously not this guy. :whiste:

there is no such thing as gps north. not sure if you are being facetious for the sake of your joke or not, if so disregard.

 

[vailr]

True north never moves so it gives you a consistent reference point for navigation.

Except that there's something called "earth wobble" that takes ~23,000 years to complete one rotational cycle. And, given a sufficiently large outside force collision from an asteroid, the outer skin of the earth could temporarily dislodge from the inner core and slide like the peel of an orange to some new geographic location. And may have actually occurred at some point in ancient history.

 

[Fritzo]

If I recall, astro-navigation is the planned standard for directional measurements on other planets. As stated, some planets do not have a magnetic field.

 

[IronWing]

Round or not...it's an object to be mapped.

OK. I have a map. How do I program a blind computer-guided probe to find the stake at point 0?

Put a beacon on it. There is no organic method of establishing a navigational reference net.

For rotating rocks with poles one can organically create a latitude system site un-seen but longitude is going to be arbitrary.

For truly non-rotating rocks I suppose one could program a probe to use a star map to establish a reference grid against suitably far away stars.

For ever so slowly rotating objects, just pount a stake with a beacon and start mapping.

 

[destrekor]

Yep, because tomorrow all our compasses are just going to point the wrong way, just like that!!!!

Besides, I was trying to be humorous and point the fact out that 'we' probably won't be around because we will have killed each other off before we see it flip.

Point 1: Yes, it is actually possible, and will eventually happen. Don't worry, mass chaos and destruction won't be apart of the event. Birds might go a bit nuts and compasses will need corrected, but in the age of GPS, it won't be a disaster.

Point 2: I'm still saying we'll be alive and kicking. I don't trust our ability to survive the long haul, but I don't suspect we'll be dead in a thousand years either.


Also, there's already been evidence that the field is growing unstable and a flip is "imminent" - instability may last a long while with local pockets of reverse polarity, but the "big flip" would likely be quick. It will probably wobble back and forth in polarity, that much isn't known for certain, but it seems routine. For human lifespan references, it might flip for a thousand years, flip back for another five thousand years, and then once again flip back to a reversal of today's polarity and maintain that for a five hundred thousand years.

Relevant image:

Edit: actually, reversals can be harmful. :hmm:
Contrary to that image, which depicts a perfect geomagnetic polarity lasting for over 750,000 years, there is one "major" event to report. A reversal occurred a little over 40,000 years ago, which was around 500 years in length with an actual reversed geomagnetic field lasting about 250 years.
http://en.wikipedia.org/wiki/Laschamp_event

It suggests field strength during the transitional times was roughly 5% of the current strength. That is certainly not a good thing for living things. If it were to coincide with nasty solar storms, yuck. Especially in this age of sensitive electronics.

 

[randay]

[*]Has no discernable rotation.

but does it rotate? if so you may be able to use a ring laser gyro.

 

[sao123]

north is an arbitrary concept, why shouldn't it have an arbitrary value?

North is the vector which is perpendicular to the universal plane which contains the most mass.

 

[MongGrel]

Why do you think he's trolling? Go do some research. The poles are overdue for a flip, based on scientific evidence.

Yep.

 

[SteveGrabowski]

We do? I'm pretty sure we use magnetic north given that every traditional compass says so. Cartographers fixated on magnetic north because it hasn't changed during humanity's written lifespan.

This thread also makes me ask the question - in space, which way is "up"?

The magnetic north pole actually moves around a lot. Even to the point you'll get different declinations for the same topographic maps printed in different years. Declination is the difference between magentic north measured by a compass and true north pointing to the axis of rotation. Hiking maps usually show declination from both true north and north star north.

 

[Hayabusa Rider]

Too easy.

Find the pole that has penguins. North is the opposite one.

 

[Ichinisan]

Too easy.

Find the pole that has penguins. North is the opposite one.

I like this answer.

 

[CZroe]

You trollin' or something? I didn't see a /s after that remark.. so......

wot?

I think it's clear that you don't realize that magnetic pole flips are not the same thing as magnetic North wandering into the southern hemisphere at 25 miles per year. The poles can change polarity to flip relatively fast. It has happened many times, but not in written human history. We are overdue for another flip. It could happen tomorrow. Heck, it could happen today.

 

[Ruptga]

Has anyone mentioned magnetic reversals yet?