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Earth's Magnetic Field Weakens 10 Percent
caryw writes "Interesting story from the AP. 'The strength of the Earth's magnetic field has decreased 10 percent over the past 150 years, raising the remote possibility that it may collapse and later reverse, flipping the planet's poles for the first time in nearly a million years, scientists said Thursday. At that rate of decline, the field could vanish altogether in 1,500 to 2,000 years, said Jeremy Bloxham of Harvard University. Hundreds of years could pass before a flip-flopped field returned to where it was 780,000 years ago. But scientists at a meeting of the American Geophysical Union cautioned that scenario is an unlikely one. "The chances are it will not," Bloxham said. "Reversals are a rare event."'"
As usual, I will probably be marked as flamebait, but sometimes people read rather than mod, so I'll post anyway. Creationists have done discussions on the earth's magnetic field before, which is one method that shows a young date for the earth: http://www.creationresearch.org/crsq/articles/39/3 9_1/GeoMag.htm
"The weakening -- if coupled with a subsequently large influx of radiation in the form of protons streaming from the sun -- can also affect the chemistry of the atmosphere, said Charles Jackman of NASA (news - web sites)'s Goddard Space Flight Center.
That can lead to significant but temporary losses of atmospheric ozone, he said.
Ozone Holes??
This is just a hair-brained idea a-la "I Love Lucy" but would it be possible to generate a fake magnetosphere in the event that we are without one for a few hundred years?
IANAP but would it be possible to place a giant electromagnet at L1 and have it deflect incoming Solar wind and particles?
It would probably have to be very powerful and possibly large (nuclear powered, 100 KM long) but would that work?
Blaze a trail to the New World
I didn't think it was too "alarmist" as towards the end they talk about the only major negative effects of a weakened magnetic field and eventual switch is a slight increase in cancer (compared with all the cancer in the world as we know it today.) It also presented the possibility of having more than 2 poles, and a positive effect of the was having the auroras being visible all over the Earth. I showed this in my Earth Science classes this weeek, as we just started talking about how magnetic reversals are recorded in igneous rock, and is one of the pieces of evidence for sea floor spreading and plate tectonic theory.
see, this is a great example of how 'left'/'right', 'up'/'down', 'positive'/'negative', 'clockwise'/'counterclockwise', and other conventions can be clung to and allowed to distort the truth.
for example, you care really badly which way compasses point, or more generally you care a lot about the polarity of magnetic fields staying how they are.
oh, really? well, do you care much at all about which way around the toilet your water swirls as it goes down the drain? of course you don't -- and it's a good thing because if you cross the equator and flush your toilet again, the water will go down the other direction.
the earth goes through a series of wobbles which lend its hemispheres 'seasons', while undergoing a process known as 'precession'. at the same time, the solar plane undergoes a bit of unsteadiness where it's located on the galaxy's arm, dipping over and under the galactic plane.
our solar system is heading toward the galactic plane, the denser part of the galaxy.
my intuition tells me that as we approach, we will notice changes in certain things that go 'one way around', either slowing or diminishing, and when we pass over -- ping? pong! -- even the magnetic field will be inverted.
but rest easy -- in this theory, you'll also be able to go to australia and experience the retro feeling of water going down the drain the way it used to in the united states.
also, magnetic pole flips aren't 'rare', they may have happened millions of times in the past at regular intervals, according to some geologists who have studied sedimentary rock layers and found that magnetically influenced particles in the sediment (settled over time,) pull this way, then that way, then this way again as they survey deeper.
"Stratigraphically the origin of agriculture and thermonuclear destruction will appear essentially simultaneous" -- Lee
As I recall from the Nova program, a field reversal was essentially caught in the act by a single layer of lava. The interior of the lava flow had frozen in it a magnetic field 6 degrees different from the field frozen in the top and bottom of the flow, which cool faster due to contact with the atmosphere and the ground. This happened in a short period of time (days or weeks?). So saying "at that rate of decline" is pointless, as the rate of change would probably increase during a reversal. To illustrate, I'd like to point out that the north magnetic pole has been migrating further north at an accelerating pace. Although the link's text claims the acceleration occurred around 1970, their map shows it started sometime between 1904 and 1948, with perhaps a brief deceleration in the '60s.
And the sun is becoming more active at the same time. Things could get quite interesting on our little planet.
"I'm so moist I'm sticking to the leather." -Kermit the Frog on The Late Late Show
The mechanism behind magnetic field reversals is poorly understood. I haven't seen any statistical analysis, but I would be interested to know if magnetic field reversals can best be modeled as periodic or as random, with some sort of variation about an expected value. It may be more accurate to say that the probablility of a reversal in any given year is increasing, rather than saying we are "overdue". Or maybe that is just splitting hairs.
Here's an article on Earth's magnetic field which appears to say different stuff to the link referenced above. "Dr. Humphreys is an ICR Adjunct Professor of Physics and a physicist at Sandia National Laboratories, Albuquergue, New Mexico. The Laboratories have not supported this work."
Here's a (linked) article celebrating his straight-over-home-plate predictions about other planetary magnetic fields from when Voyager II validated his predictions. The Sandia footnote has this interesting appendix: "and they neither affirm nor deny its scientific validity.".
It's not linked above, but here's the CRSQ article which led to all of the fuss. The next Mercury flyby that measures magnetic fields should be interesting.
I'm fairly sure none of this includes direct mention of the Earth's core fields, so either the article I have in mind wasn't written by Humphries or I've missed it somewhere along the line.
Got time? Spend some of it coding or testing
It's interesting to see that the majority opinion on the temporary loss of a net magnetic field (i.e., no magentosphere) would be nothing more than an inconvenience for satellite communication and herald the introduction of SPF 80.
IAAP. If we assume the Earth had no magnetosphere, and the soloar wind was not being routed to the poles, then the Earth would essentially be a very massive comet.
Solar wind has a lot of linear momentum (the proton density is small, but protons have lots of mass). Momentum is always conserved, but because of the field, the momentum is being transfered to the Earth through the coupling of the solar wind and the magnetic field (and since the solar wind impacts the atmosphere only at the poles, there is no net change). Now the Earth is pretty darn heavy, so the solar wind is like nothing at all.
Now consider the scenario if there is no field (or a bunch of randomly aligned fields). The solar wind hits the atmosphere everywhere on the day side. Wow! Aurora Universalis!! How pretty! That's true for a while. More importantly, momentum transfer is now occuring through interactions with the atmosphere. Ever see the tail of comet? That's the same thing, exepct in that case the solar wind is interacting with really cold water (solid ice). The atmospheric blanket that surrounds our planet is incrediblly light, and would essentially be blown off in a very short amount of time. (Comets survive since the tend to spend the majority of their existance out beyond pluto where the proton density is REALLY low, they only brighten up when the come visiting our neck of the solar system, which is many cases, is farther from the sun then we are). We could be talking a matter of decades, or even years until the Earth lacked an atmosphere.
This leads to the obvious question. If the Earth does lose its atmosphere every 1-2 million years. How does complex land dwelling life evolve?
This is the problem of knoing too much physics and staying up until 6 am.