What should you expect from a planet where you can't trust a compass to point the way you're used to? The magnetic field does more than provide compasses a reference point: It shields us from the full impact of the solar wind — charged particles emitted from the sun that would otherwise bombard us with ultraviolet radiation.
The origins of the magnetic field start thousands of miles beneath Earth's surface, where convection in the outer core produces electrical currents that, in combination with Earth's rotation, create and sustain a magnetic field that runs through the planet like a bar magnet with two poles, north and south aka the dipole.
When we talk about Earth's magnetic field flipping, we mean an event where those poles reverse. Based on information stored in cooled lava rocks, we know this has already happened before — about times in the last million years [source: Fleming ]. The last time it happened was , years ago, though a temporary reversal occurred 41, years ago and lasted less than 1, years [source: Livermore and Mound ]. The causes of these reversals remain mysterious, and there's no way to fully predict when the next one might occur [source: Roach].
However, we know that a flip doesn't happen overnight. Instead, it takes anywhere from a century to 20, years to complete, and it's accompanied by a decline in strength of the magnetic field. The last reversal happened , years ago during the Stone Age, and indeed there's evidence to suggest the planet may be in the early stages of a pole reversal right now.
But should we really fear this event? What will actually happen when north-pointing compasses make a degree turn toward Antarctica? Will the continents tear themselves apart, or are we in store for much more mundane changes? Earth's magnetic field takes between 1, and 10, years to reverse, and in the process, it greatly diminishes before it re-aligns.
According to John Tarduno, professor of geophysics at the University of Rochester, a strong magnetic field helps protect Earth from blasts of radiation from the sun. With a weak field, this shielding is less efficient. The charged particles bombarding Earth's atmosphere during solar storms would punch holes in Earth's atmosphere, and this could hurt humans. These 'holes' would not be permanent, but might be present on one- to year timescales — arguably important enough to be a concern in terms of skin cancer rates," Tarduno said.
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Animals This frog mysteriously re-evolved a full set of teeth. Animals Wild Cities Wild parakeets have taken a liking to London. Animals Wild Cities Morocco has 3 million stray dogs. Our modern way of life could cease to exist. We know this because we're already seeing a glimpse of this in an area called the South Atlantic Anomaly. Turns out, the direction of a portion of the magnetic field deep beneath this area has already flipped! And scientists say that's one reason why the field has been steadily weakening since As a result, the Hubble Space Telescope and other satellites often shut down their sensitive electronics as they pass over the area.
And astronauts on the International Space Station reported seeing a higher number of bright flashes of light in their vision, thought to be caused by high-energy cosmic rays that the weaker field can't hold back. Since experts started measuring the Anomaly a few decades ago, it has grown in size and now covers a fifth This is so extreme that it could be a sign we're on the brink of a polar flip, or we may already be in the midst of one! Mitchell: They don't know.
The last time the poles reversed was , years ago so it's not like we have a record for this. Mitchell: In the past 65 million years since the last mass extinction there have been reversals roughly every , years. So what gives? Well, scientists haven't figured it out yet.
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