Surprising somebody hasn't dropped in the "It's Aliens" meme yet...

You just did, didn’t you?

quote:

Originally posted by frayedends:

quote:

Originally posted by Chris42:
Frayed - the problem has to do with compass inaccuries - the shipping north of Canada is rather close to the pole (relatively speaking). If the magnetic pole moves they can’t tell, by compass, where they are. If the magnetic field around the world shifts, the satellites that sense that field get thrown off too.

Kind of like sailing off shore and using a lighthouse as a reference, but someone keeps moving the lighthouse -

Surely there must be some technology to overcome this. Like GPS or something.

when I learned to sail, and finally earned a Captains license, the proper navigation method was to use Magnetic north along with a variance +/- for local magnetic field offsets. compute the direction, add or subtract for compass course, adjust for compass reading by adding or subtracting variance, then plot your heading.

as a blow boater, just using compass heading without the added math was always "good enough" for coastal sailing.


it would be interesting how this is being handled by current GPS technology. or if the old Loran system would be affected by shift in magnetic fields?


tymll

quote:

Originally posted by ds1962:
If the poles shift we will be in deep doodoo.

I wouldn't worry too much about the Poles, they are staunch allies.

Interesting (or maybe not) bit of aviation trivia here: Aeronautical navigation charts are printed on a grid, with the vertical lines oriented to true north.

VORs transmit navigation signals that are oriented to magnetic north. Or, are they? Maybe not.

The difference between true north and magnetic north, at any given location, is magnetic variation, usually shortened to just "variation."

When planning a flight that will use the magnetic compass in the airplane as the primary navigation aid (yes, we still do this for some flights, even in the age of GPS), the course line on the chart shows the desired track with respect to true north. The local variation, as determined by isogonic lines on the chart is added (for westerly variation) or subtracted (for easterly variation) to obtain the magnetic course. Standard stuff.

Now, if we use VORs for navigation, the signal transmitted by the VOR is already referenced to magnetic north, so no further correction is needed for variation. But wait, there's a catch. Because the magnetic north pole drifts around a bit, the variation at any given location might differ a bit from year to year. Magnetic north for VORs, as depicted on the chart, is not updated and is not necessarily current. It is shown on the charts as it was, at the time that the VOR station was commissioned, so there might be a difference between magnetic course as calculated using current variation, and magnetic course derived from a VOR.

The preceding little known fact was brought to you by Cliff Clavin.

quote:

Originally posted by ds1962:
If the poles shift we will be in deep doodoo.

Will my toilet flush in the opposite direction?

That'd be cool.

So, the South Pole is still on break?

It's from moving earth & building heavy objects.
Throwing the balance off.
I'm surprised the ppl that protect the earth haven't made laws covering global weight distribution.

I guess it's time to learn how to use a sextant.

I hope Guam doesn't tip over!

0-0

quote:

Originally posted by 9x18:
Yea, well, they'll really be upset when we have a complete magnetic reversal.

https://en.wikipedia.org/wiki/Geomagnetic_reversal

I thought this was common scientific knowledge. Apparently only to bona fide scientists. The sky is falling bullshit never gets old.

I didn't think anyone would notice. Sorry... I'll put it back.

If I can remember how

quote:

Originally posted by Gustofer:
Will my toilet flush in the opposite direction?

Not unless the earth reverses the direction of its rotation, or you move to the southern hemisphere. While it is true the direction of the rotation of the flush is not strictly due to the coriolis effect, it surely is not related to magnetism.

Disclaimer: Snopes apparently disagrees with my college professors, so YMMV.

quote:

Originally posted by eltonr:

it would be interesting how this is being handled by current GPS technology. or if the old Loran system would be affected by shift in magnetic fields?


tymll

Loran operated on essentially the same principles as modern GPS.

Both systems use stations transmitting synchronized signals. The user receives these signals, which are no longer synchronized because he is different distances from the different stations, so the signals take different amounts of time to reach him. By precisely measuring the offsets between the signals and referring to the known locations of the stations, the user can triangulate his position. It's just that Loran used ground stations and GPS uses satellites, and GPS is a lot newer so the stations are better synchronized and the users can measure the offsets more precisely.

In either case, magnetic north has nothing to do with the process.

They are more expensive than magnetic compasses, but many boats and I expect virtually all ships have gyrocompasses on board. A gyrocompass is a fascinating instrument that uses gyroscopic precession to automatically align itself with the axis of the rotation of the earth (true north). No dependence on the Earth's magnetic field at all.

Modern sensor technology has actually advanced to the point that now there are "gyrocompasses" that don't actually have gyroscopes in them - they can measure the movement of the instrument with enough precision that they can simply measure the rotation of the earth directly (yes, even in a moving vessel!) and determine the axis of rotation.

Like erasing a giant Etch-e-Sketch.

New York Times just said Trump did it!

The following professionals were quoted to predict (these are a couple of the leading scientists in these matters) :

quote:

Dr. Raymond Stantz: Fire and brimstone coming down from the skies! Rivers and seas boiling!

Dr. Egon Spengler: Forty years of darkness! Earthquakes, volcanoes...

Winston Zeddemore: The dead rising from the grave!

Dr. Peter Venkman: Human sacrifice, dogs and cats living together... mass hysteria

quote:

Not unless the earth reverses the direction of its rotation, or you move to the southern hemisphere. While it is true the direction of the rotation of the flush is not strictly due to the coriolis effect, it surely is not related to magnetism.

Please explain why when 2 dogs meet, butt-sniffing rotation occurs counter-clockwise? If the poles are reversed, will they start butt-sniffing clockwise?