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We can even see a magnetic field in the oceans when we’re looking at the data collected by low Earth orbiting satellites. So because the oceans are a salty water, as they move around they also generate a magnetic field in a rather similar way to the Earth’s core itself. And we can see the ocean tides even.
The moon being a bit smaller, colder, smaller and made principally of crust material doesn't have that iron core that's liquid, spinning around making that magnetic dynamo effect, and therefore doesn't have that magnetic field. If we didn't have that magnetic field on Earth we would largely resemble Mars: a dried out prune of a planet because ...
The animals were tested in the dark to avoid giving them light-related cues. A set of coils were used to generate a magnetic field that cancelled out the planet's natural field and then applied its own. The researchers varied the orientation of this field, which was equivalent in strength to the Earth's own magnetic field, in 10 degree steps.
Stuart - Yeah! It has geographic poles – these as the two points on the surface of the globe which the earth rotates around. But it also has magnetic poles. These are where the Earth’s magnetic field lines flow in and out of the earth’s surface. But the magnetic and geographic poles aren’t the same – they’re a few hundred kilometres ...
The Earth's magnetic field does seem to flip every few hundred thousand years and we're overdue for one at the moment. A few years ago they thought this would take hundreds of thousand of years for it to flip slowly. But recent evidence suggests that it'll maybe flip over faster. In the process of it flipping over it doesn't tend to flip over ...
So a great big globe of liquid iron and nickel as Jan says. As it cooled down, it started to solidify. So, in the centre of the Earth now, we have an inner core which is about a thousand kilometres in diameter which is solid and then the outer core is liquid. It's the movement of this outer core in fact that makes the Earth's magnetic field.
Chris - Because one other argument was that Mars used to have a nice atmosphere, rather like we've got, but that having lost its magnetic field, possibly because it cooled down because it's a much smaller planet, that magnetic field loss meant that the wind coming from the sun, the solar wind, was then able to pluck away, slowly eroding away ...
There's no reason why the magnet shouldn't carry on. Chris - It's basically not burning off any energy to make the magnetic field, and it's something interacting with the field that actually makes an effect rather than the other way around. Diana - But why is it then that some magnets get demagnetised over time? Dave - Okay.
Connie - So this paradox lays out a problem. We have a highly conducting molten core of iron but, if it's highly conducting, then either: 1) the Earth's magnetic field couldn't have been around for that long, it would have burnt itself out. And we have rocks that date back almost to the beginning of the Earth showing its presence.
Liam Messin set out to answer this attractive question with Tim Boyd, a Cambridge undergraduate...Tim - Thinking of magnets having a north and south pole is slightly misleading. They have a thing known as a dipole. This means that they have one pole with a north and south end, but it is a little more complicated than that.