Switching Poles...

[Eclogite]

The movement of the earth's magnetic field during the Miocene period was quite impressive. If we assume it moved 30 degrees per year, that is about 2000 miles per year or roughly six mile per day, or about 1/4 mile per hour.

I'm at something of a loss to understand how we would know this. Can you offer some citation?

[LaurieAG]

Hello Boerseun,

 

This being the case, any birds dependent on magnetic navigation should have had problems long ago, leaving only those navigating by sight or other means to continue the line.

 

Like the 10,000,000 that washed up on dead of exhaustion (lactic acid build up) on the south east coast of Australia around 4/5? years ago. At the time there were several issues with satellite navigation around the world, Greek ferrys and a cargo ship on the great barrier reef to name a few.

 

These events occurred, not from a planetary polarity change, but something else that didn't effect all things equally (like it was moving/orbiting).

 

Probably the most important impact on modern human society will be how safe are electronics that utilise earth return (or all electronic earths for that matter) circuits. If the circuit doesn't work both ways (modern cars are a good example of what happens if you reverse the polarity, unlike the older cars) then expect things to burn out or stop working.

[ggoodknight]

If you look at any proper map, it'll show you the magnetic variance to proper North, and the annual shift. Magnetic North is quite a distance from True North, and keeps on moving, as the Earth's guts keep on churning. This shift is well-documented, although, with the advent of GPS this addendum to maps might dissapear - its only usefull for Boy Scouts using magnetic compasses.

 

No, it's needed on a regular basic by pilots. GPS is really not that reliable to bet your life on, and aviation maps all have the local magnetic variance clearly marked. I believe even the most sophisticated airliners still have a magnetic compass somewhere in the panel (although that could have possibly changed in the last year or so).

[CraigD]

If you look at any proper map, it'll show you the magnetic variance to proper North, and the annual shift. Magnetic North is quite a distance from True North, and keeps on moving, as the Earth's guts keep on churning. This shift is well-documented, although, with the advent of GPS this addendum to maps might dissapear - its only usefull for Boy Scouts using magnetic compasses.

No, it's needed on a regular basic by pilots. GPS is really not that reliable to bet your life on, and aviation maps all have the local magnetic variance clearly marked. I believe even the most sophisticated airliners still have a magnetic compass somewhere in the panel (although that could have possibly changed in the last year or so).

Ggoodknight makes some good points, I think, about the continuing value of pre-GPS navigation systems, to which I can’t resist adding some of my own :doh:

 

Nearly all aircraft, light through heavy commercial, continue to carry high-quality magnetic compasses little different in basic construction from those of the late 19th century. In most light aircraft, the magnetic compass is used to manually set a gyrocompass (after starting the engine, as the magnetic effect of its ignition system substantially changes the magnetic compass reading, an effect precisely compensated for following construction or major maintenance), which is actually used during flight, as normal flight motion causes even well-dampened magnetic compasses to fluctuate (“swing”) too much to be used with much accuracy. The gyrocompasses on more expensive aircraft, including, I suspect, those in airliners (I’ve never actually sat and fiddled in the cockpit of anything larger than a 10-passenger corporate jet) are automatically “slaved” to a concealed magnetic compass, essentially setting themselves. Every cockpit I’ve seen still has a visible magnetic compass, for checking that the slaving compass is working correctly, and as backup in case of malfunction of the primary instrument.

 

In basic operating principle, GPS is unsuited for measuring the direction a vehicle is pointed (or “heading”). Although many GPS receivers provide a directional reading resembling a compass, this actually shows the direction of the vehicle’s travel, not its true heading. For a slow aircraft in a strong wind, a boat in a strong current, etc, these two kinds of readings may disagree considerably.

 

Even though many small and large aircraft use GPS systems for routine navigation, the primary navigation systems used by all aircraft are the VORs installed in the 1950s and 60s at most airports and major waystations. You can (and every pilot I know still does) turn up the volume on a VOR nav radio and listen to it identify its station with a short voice message and its abbreviation in Morse code.

 

A similar kind of system, shorter-range and 3-dimensional, ILS, continues to be the used for approach and landings – although GPS has been capable of operations of this kind for over a decade, there’s been reluctance to use it as a primary system, vs. the old (first installation and use in 1936), proven ILS systems. Also, most GPS receivers, even those in expensive aircraft navigation systems, are accurate only to about 10 m, making them suitable only for the lowest-level of US ILS certification, “Category I”, for which FAA-certified adoption is currently (as of 1997) under way. Cat I operations require 800 m horizontal visibility and that the ground be visible from an altitude of 60 m above it, vs. the highest certification level of a non-GPS ILS, Cat III C, which allows “zero-zero” operation – that is, landing completely blind.

 

While GPS is tremendously useful, it doesn’t appear poised to eliminate the previous century’s radio navigation systems anytime soon. In the event of some catastrophe causing the maintenance of the GPS constelation.

[ggoodknight]

The gyrocompasses on more expensive aircraft, including, I suspect, those in airliners (I’ve never actually sat and fiddled in the cockpit of anything larger than a 10-passenger corporate jet) are automatically “slaved” to a concealed magnetic compass, essentially setting themselves.

 

The heading gyros (aka Heading Indicator or HI) that are slaved to a magnetic fluxgate are generally Horizontal Situation Indicators (HSI) that are combination gyrocompass/VOR/ILS indicators. Very cool. Some GPS navigators present the information in the same way and it is very easy to use when flying by instruments.

 

Every cockpit I’ve seen still has a visible magnetic compass, for checking that the slaving compass is working correctly, and as backup in case of malfunction of the primary instrument.

 

Yes, they have been required equipment for all certificated aircraft.

 

 

In basic operating principle, GPS is unsuited for measuring the direction a vehicle is pointed (or “heading”). Although many GPS receivers provide a directional reading resembling a compass, this actually shows the direction of the vehicle’s travel, not its true heading. For a slow aircraft in a strong wind, a boat in a strong current, etc, these two kinds of readings may disagree considerably.

 

Even though many small and large aircraft use GPS systems for routine navigation, the primary navigation systems used by all aircraft are the installed in the 1950s and 60s at most airports and major waystations.

 

Actually, nowadays air traffic controllers pretty much expect that even aircraft whose designators do not show they are equipped with a GPS at least has a handheld GPS. While the airways continue to be defined by VOR placements, the primary nav really is GPS and the FAA's policy has been that the terrestrial navaids will be decommissioned as they age.

 

 

You can (and every pilot I know still does) turn up the volume on a VOR nav radio and listen to it identify its station with a short voice message and its abbreviation in Morse code.

 

This is required, though if you are using a GPS to fly the VOR defined Victor airways you don't verify the VOR because your NAV gear isn't really using the VOR, it's just assuming the VOR is where the database says it is.

 

A similar kind of system, shorter-range and 3-dimensional, continues to be the used for approach and landings – although GPS has been capable of operations of this kind for over a decade, there’s been reluctance to use it as a primary system, vs. the old (first installation and use in 1936), proven ILS systems.

 

It is unclear to me that the "ILS" first used in a very few airliners at a very few airports in '36 (or '38) is the final ILS system that was put into wide use later. I have seen a number of claims that the first of the modern ILS systems was at Arcata, California, a site with the most foggy days of any US airport (and coincidentally the airport I flew my first solo IFR ILS approach through the coastal stratus).

 

A standard ILS approach will generally give a private aircraft guidance down to 200' above ground level, at which time if you can't see the runway you start a climb, pronto. GPS approaches can bring you down almost as low.

 

 

While GPS is tremendously useful, it doesn’t appear poised to eliminate the previous century’s radio navigation systems anytime soon.

That is in process and is the policy of the US FAA. A sticking point among many is that there is a defacto monopoly for the database updates required for operation, by a company called Jeppessen. It galls many that Jepp rakes in a bundle of money for repackaging information that the FAA generates.

[pmaust]

Perhaps these shifts that have windows that allow lots of harmful radiation may be one of the keys in explaining genetic mutations for evolution? This would greatly increase the mutation rate above the "normal" and could perhaps be yet another mechanism for change.

 

If I were a betting person, I'd bet on some more new extinctions occuring. What evidence in nature do we have that adaptation to radical environmental changes happen quickly enough to save most creatures? Adaptation through mutation appears to be a very slow process in most instances. This sounds like a potententially interesting new topic. :evil: