The Core

The Core Photo Credit: Clipart.com

In the recent movie The Core, intrepid explorers called "terranauts" burrowed down into the earth's fiery center to fix a freak malfunction in the planet. Although sending humans to the core is pure science fiction, this Science Update tells of a recent proposal to send a robotic probe to this uncharted territory.


A road map to the earth's core. I'm Bob Hirshon and this is Science Update.

In 1864, author Jules Verne wrote of a fictional "Journey to the Center of the Earth." In a recent letter to the journal Nature, Cal Tech planetary scientist David Stephenson proposed a possible way to get there.

He says a small, unmanned probe could be sent to the rim of the earth's fiery core—first by blowing open a deep crack in the earth, and then filling the crack with hot molten iron.


And then because of the force of gravity acting on the heavy iron, the crack will open up at the bottom and travel through the earth, closing up behind as it goes.

As it oozes downward, the molten iron would carry the grapefruit-sized probe to the core. Once there, the probe would transmit information about the core's composition—which could shed light on our planet's origins.

Stephenson's letter doesn't go into practical details. He says his goal is just to plant a seed for future thought.


Many of the scientists who have read my paper laughed out loud when they read it. And I'm delighted by that response. I'm also hoping that there are some people who will laugh, but will also take it seriously enough that they will store it away as an idea that is worthy of more attention.

For the American Association for the Advancement of Science, I'm Bob Hirshon.

Making Sense of the Research

If this sounds like a wild idea, you're right. Even Stephenson, who's proposing the idea, would admit that it's wild. But there's a crucial difference between wild and impossible, and that's his point. Centuries before the Wright Brothers, Leonard da Vinci sketched out wild ideas for machines that would allow humans to fly. Early in the 20th century, the biologist Alexander Fleming introduced the wild idea that penicillin from bread mold might be used to fight diseases. Years would pass before anyone tried to make it practical. The author Arthur C. Clarke wrote about the idea of space stations decades before they became reality.

In fact, all practical advances in science and technologies were once just wild ideas. And today, there's an organized way that scientists can present them: they can publish their thoughts and let the seed germinate in other people's minds. In many cases, nothing will come of it. In some cases, the idea will be developed further and then abandoned. But once in a while, it leads to something that works.

So what do we know about Stephenson's proposal right now? Probably the biggest question mark is how to rip a kilometer-deep hole in the earth to get the whole thing started. There's no question that we can do it—we do have nuclear weapons—but how to do it safely is another question.

As for the liquid iron transport system, that's just mimicking something that happens naturally inside the earth all the time. A volcano is just molten rock and metal that's risen up from the earth's interior and cracked through the surface. Stephenson's proposal is merely to reverse the process, by dumping liquid iron into a man-made hole.

The temperature at the earth’s core is 3000 degrees Celsius. That's way too hot for people, but an unmanned device could probably survive it. We do know of materials that can stay solid at such high temperatures. In fact, the earth's core itself is believed to be solid—that's why Stephenson's trip could reach only the edge of the core. So if a probe could be built from materials that could withstand such high temperatures, it could make it. And although the high temperatures would tend to melt or vaporize most materials, the incredible pressure at the earth's core helps to keep things solid.

The remaining question is: Why go through all the trouble? It's a good question, and it may turn out that the trouble and expense isn't worthwhile. But if a plan like this could be made practical, it would mark the first time that humans had direct evidence of the composition of the earth's core. Understanding the earth's composition could enhance our understanding of how the planet functions. And most importantly, it could open the door to new information that we might never have thought was there.

Now try and answer these questions:

  1. How does Stephenson propose reaching the earth's core?
  2. What are some of the questions that would need to be answered in order to develop this idea further?
  3. What is the purpose of publishing proposals of this nature? If you were the editor of a scientific journal, and someone submitted an "idea paper" like this one, how would you decide if it was worthy of publication? Give specific examples of rules or criteria that you would use in your judgment.

For Educators

Savage Earth Animation, part of the PBS Online website, features an animation of the layers of the earth and shows how the processes beneath the earth cause earthquakes, volcanoes, and other violent natural occurrences.

The Earth's Layers, from the Volcano World site, is an interactive tutorial on the inner structure of the earth.

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