In the 1970s, Soviet scientists embarked on a mission to drill the world’s deepest borehole.
The target was 15,000m, or 15km.
Although they fell short of this depth due to the heat encountered, they did succeed in the first aim, and the wonderfully-named Kola Superdeep Borehole remains the deepest hole on Earth.
Eventually reaching a depth of 12km, which is still deeper than the deepest depth of the deepest ocean, work on the borehole near the small Russian border with Norway was eventually stopped 24 years after it had begun.
Such a groundbreaking project requires groundbreaking technology, and an entirely new kind of drill had to be invented for this one. To get readings from the very bottom, new types of instruments also had to be created.
It’s true that we know more about some distant galaxies than we do the Earth beneath our feet, which is why the Soviets embarked on this endeavor.
So what did they learn?
Check out the video from SciShow above to see!