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In the 19th century, it was generally thought that man would reach the center of the Earth long before he reached the Moon . This shows just how unpredictable technology can be. A journey to the centre of the Earth is actually much more difficult than it sounds.
The pressure at the centre of the earth is enormous because, quite literally, entire weight of the earth is on top of you. This is no known substance, not even carbon nanotubes, that can maintain its shape at such a great pressure. While the Earth's deep interior may offer vast amounts of energy, its may be quite a while before we can tao into it directly...
Such a nice article hope you'll do better in future