4 ms·

As it says in the article, we don't have anything to fear at the surface. Reversals have never been associated with increased extinction. When the field does re

As it says in the article, we don't have anything to fear at the surface. Reversals have never been associated with increased extinction. When the field does reverse, it becomes increasingly disordered with higher-order moments dominating. If I recall, the dipole moment of Earth's magnetic field is normally over 90% of the strength. The higher-order moments dissipate faster, so it doesn't reach as far into space.

pbhjpbhj 8y ago
Given there are lots of species that use the Earth's magnetic field for navigation this is highly surprising. Perhaps there have been mass extinctions but they're not readily found, or our timings are wrong so they don't appear synchronised? I wonder if there wouldn't be more seismic activity?
- njarboe 8y ago
  The magnetic field also gets very weak (90% drop in intensity and the magnetic pole way down near the equator) quite often. These are call magnetic excursions. They happen at an average frequency of maybe 50 thousand years or so with a high variance. The last big one is called the Las Champ excursion and happened about 41 thousand year ago. Species that needed a strong magnetic field that points north or south to exist would have gone extinct long ago. These species must have ways to survive when the Earth's magnetic field is unstable and weak because that happens on timescales much shorter than species evolution. [1]https://en.wikipedia.org/wiki/Laschamp_event https://en.wikipedia.org/wiki/Laschamp_event
  - lenticular 8y ago
    That's interesting. Magnetic reversals actually take some time to complete (a few thousand years). If it changes slowly enough, if animals navigate through a learned magnetic field rather than genetic instinct, they'd do fine.
- Izkata 8y ago
  > there are lots of species that use the Earth's magnetic field for navigation And (possibly) one directly for hunting: http://blogs.discovermagazine.com/notrocketscience/2011/01/11/foxes-use-the-earths-magnetic-field-as-a-targeting-system/ http://blogs.discovermagazine.com/notrocketscience/2011/01/1...

pbhjpbhj 8y ago

Given there are lots of species that use the Earth's magnetic field for navigation this is highly surprising. Perhaps there have been mass extinctions but they're not readily found, or our timings are wrong so they don't appear synchronised? I wonder if there wouldn't be more seismic activity?

njarboe 8y ago
The magnetic field also gets very weak (90% drop in intensity and the magnetic pole way down near the equator) quite often. These are call magnetic excursions. They happen at an average frequency of maybe 50 thousand years or so with a high variance. The last big one is called the Las Champ excursion and happened about 41 thousand year ago. Species that needed a strong magnetic field that points north or south to exist would have gone extinct long ago. These species must have ways to survive when the Earth's magnetic field is unstable and weak because that happens on timescales much shorter than species evolution. [1]https://en.wikipedia.org/wiki/Laschamp_event https://en.wikipedia.org/wiki/Laschamp_event
- lenticular 8y ago
  That's interesting. Magnetic reversals actually take some time to complete (a few thousand years). If it changes slowly enough, if animals navigate through a learned magnetic field rather than genetic instinct, they'd do fine.
Izkata 8y ago
> there are lots of species that use the Earth's magnetic field for navigation And (possibly) one directly for hunting: http://blogs.discovermagazine.com/notrocketscience/2011/01/11/foxes-use-the-earths-magnetic-field-as-a-targeting-system/ http://blogs.discovermagazine.com/notrocketscience/2011/01/1...