LIKE the 1864 classic science fiction novel by Jules Verne, humankind has always wondered what we'd find were we to undertake a 'Journey to the Centre of the Earth'.

With drilling only delving some seven miles into the Earth, we have to rely on other technology to unravel what is at the Earth's core.

In a recent science paper, the understanding that the Earth is made up of four main layers: crust, mantle, outer and inner core has been challenged.

"It's very exciting - and might mean we have to re-write the textbooks!" said Australian National University geophysicist Joanne Stephenson, lead author of the newly published work.

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Using seismic wave technology, Stephenson and her colleagues deduced that the inner core has an inner core itself. The technology is not dissimilar to that of 'echolocation' used by bats and dolphins.

This potential “innermost inner core” may have been caused by a dramatic event early in Earth’s history added Ms Stephenson.

"The details of this big event are still a bit of a mystery".

So what are these 'structures'?

Within the Earth's inner core, a sort of dense metal ball which is only slightly smaller than the moon, Stephenson and team found structural differences in the iron, the first detection of an even more-internal core.

While data about the core is slowly becoming more robust, it still remains sketchy.

However, there’s enough for scientists to be fairly sure Earth’s magnetic field which protects us from much of the harmful radiation for space is still controlled by the core.