Scientists Finally Have Live Proof That Earth's Core Is Solid

Researchers from the Australian National University are confident they have found direct proof, for the first time, that the earth's inner core is solid-albeit a little bit squishy.

In a paper published in the newspaper Science, Hrvoje Tkalčić and Than-Son Phạm describe how they detected so-called "shear waves" or "J waves" in the inner core. These are a type of wave.

"We found the inner core is indeed solid," said Tkalčić said in a statement.

"It turns out to be okay-the inner core shares," he continued. "The inner core is like a time capsule, if we understand it we'll understand how the planet was formed, and how it evolves."

Inner core shear waves are so weak that they can not be observed directly. In fact, detecting them has long been considered the "Holy Grail" of global seismology since the first predicted the center of the Earth was solid in the 1930s and 1940s.

The researchers used an approach that looked at the similarities between the signals and the peers of receivers after a major earthquake. This technique has been used by the same team to measure the thickness of the ice in Antarctica.

"We're throwing away the first three hours of the seismogram and what we're looking at is a big earthquake happens," Tkalčic said. "We want to get rid of the big signals."

An illustration of the Earth's structure. Scientists now have a solid proof that Earth's core is, well, solid. iStock

"Using a global network of stations, we take every single receiver and every single large earthquake-that's a lot of the same-and we measure the similarity between the seismograms," he said. "That's called cross-correlation, or the measure of similarity. From those similarities we construct a global correlogram-a sort of fingerprint of the earth. "

These results have been used to demonstrate the existence of inner waves. Despite the new insights, there is much that remains a mystery about the center of the Earth.

"For instance, we do not know yet what the exact temperature of the inner core is, what the age of the inner core is, or how quickly it solidifies, but with these new advances in global seismology, we are slowly getting there, "Tkalčić said.

"The understanding of the earth 's inner core, and the fact that there is no life on earth' s surface," he said.