Last night was revelatory to me – I watched a programme about the centre of the earth on BBC Horizon, and was shown how mistaken I have been for my entire life, in the idea that the earth under my feet is solid. Not only is the centre of the earth as hot as the sun, and molten, thus fluid, but now the scientists believe there to be a further inner core that is solid. Earth has a molten outer-core, “an enormous ocean of white hot molten metal that’s almost as runny as water’ as large as Mars and an inner-core – a solid metal ball almost the size of the Moon.
The bulk of the Earth’s magnetic field is generated not in the inner-core but in the molten metal of the outer-core. This acts as a massive electromagnetic dynamo powered by the Earth’s rotation and the long-term cooling of the planet.
Scientists believe the solid inner core is made of an iron-nickel alloy. Because of the characteristics of the iron-nickel under the conditions of heat and pressure at the centre, the crystals effectively are fluid, and can create changes to the magnetic fields that in turn effect life on earth and beyond.
By studying two phenonemon simultaneously, one scientist spending ten years of his life experimenting with iron nickel under extreme conditions, and the experience of scientists finding satellite equipment behaving erratically in space, the opportunity to investigate the magnetic fields and their effects led to new understanding of the relationship between the centre of the earth, and space.
The Earth’s magnetic field has been steadily weakening over the past 180 years. And there is one patch that is weakening faster than any other. It is an area scientists have dubbed the “South Atlantic Anomaly”, which sits over the South Atlantic and the centre of South America.It is a known hazard for spacecraft because it creates a dip in the field, allowing charged particles into the orbit of satellites and upsetting their electronics and instrumentation. When scientists mapped the Earth’s magnetic field down to the level of the outer-core, they discovered that under the South Atlantic Anomaly the simple north-south divide we know at the surface had broken down. There are patches where the field has actually flipped and points north instead of south.
So what? Well, birds migratory habits may have to change, when up becomes down,and down becomes up, bees become madder than ever, and maybe, just maybe, we will look out from our windows in UK and be able to see the magnificence of the Northern Lights. And the scientists in charge of the satellite equipment can rest a bit easier, knowing they just need to turn them off whilst they hang over the South Atlantic Anomaly, where the equipment goes potty because it is attacked by protons . Where there are ‘holes’ in the magnetic field, there is a lack of protection from these protons, and thus the results appear gobbledegook.
You might wonder how this theory is arrived at, since it is more than hot down there, the deepest we have mined is 12 km, and the centre is about 6000 km , so we’re only able to scrape the surface. Seismology has allowed scientists to sense right into the core of the planet. The seismic waves generated during major earthquakes travel from one side of the Earth to the other, allowing scientists to build up a picture of the interior. If you want to know more, I can refer you here http://www.bbc.co.uk/science/earth/surface_and_interior/inside_the_earth and good luck on your journey to the centre of the earth!
or alternatively watch the programme on here http://www.bbc.co.uk/programmes/b0148vph