Above the north pole, beyond a room's walls

[Baby Astronaut]

When answering questions of how can space never end, a typical answer-in-question-form is "what is above the North Pole?" or "if the universe were a room, what is beyond the walls?" and then in self answer "-nothing".

 

I see a flaw in those analogies.

 

Obviously, above the North Pole is atmosphere, space, planets, dust, stars. And beyond the room's walls are other rooms with more walls or the great outdoors.

 

Doesn't it seem like when a caveman might say nothing exists beyond the horizon? No offense to anyone, just what it comes across as.

 

Anyone else feel that way?

[big314mp]

Well, the analogy is usually "What is north of the north pole" which makes a little more (less?) sense.

[Baby Astronaut]

Same conclusion. North of it is the stars, galaxies, etc

[dirtyamerica]

Same conclusion. North of it is the stars, galaxies, etc

 

The stars, et. al. are above the north pole.

 

I get the analogy. Nothing is north of the north pole because you physically can't go any farther north, just like you cannot go outside the universe.

[D H]

Same conclusion. North of it is the stars, galaxies, etc

North never points up. It is always horizontal to the surface (horizontal to the reference ellipsoid, to be exact) -- except at the North Pole of course, where "north" is not defined. Any direction horizontal to the surface at the North Pole is south.

[Mr Skeptic]

If you use a spherical coordinate system, then you could also say that any direction with a north component and an altitude component is northward, but straight north would be motion on a sphere. But you could argue that any direction toward the north side of the axis of rotation is north, even if you no longer travel only on the surface. The old timers really didn't have to worry about that as they couldn't fly nor go into space.

[D H]

If you use a spherical coordinate system ...

People who have to do navigation, or geodesy, or surveying, or cartography, or ... for a living generally don't use spherical coordinates. The Earth is a spheroid, not a sphere, so professionals (and any maps you have strewn about your car or house) use geodetic coordinates -- i.e., an ellipsoidal reference system. Latitude, for example, is not the angle subtended by a line to the center of the Earth and the Earth's equatorial plane. Rather, it is the angle subtended by a line normal to the surface (the reference ellipsoid, actually) and the Earth's equatorial plane. The difference between geocentric and geodetic latitude at 45 degrees north is about 12 arcminutes, or 22+ kilometers.

 

...then you could also say that any direction with a north component and an altitude component is northward

That's akin to saying that a heading of 1 milliarcsecond north of due east is northward.

 

We live in a three dimensional universe (at least that is how it appears to be), so another dimension is needed to describe position (or velocity, or whateve) in three space. That other dimension is of course down (or up, depending on whether you are talking to an airplane pilot or a gunnery seargent). Working with angles is a royal pain, so people use locally cartesian coordinate system instead. The two standard systems are north-east-down and east-north-up. Unless qualified with geocentric, north is geodetic north and up/down is normal to the reference ellipsoid.

Edited October 21, 2008 by D H
Grammar