Sometimes, it might seem like we know everything about Earth.
Look at these pictures.
But there is a lot that we still do not know about Earth!
How many caves are there on Earth?
No one knows. Many caves have never been explored by humans.
The deepest cave in the world, Krubera, has never been explored fully.
No one has ever been to the deepest parts of Krubera.
More than 3,500 people have climbed to the top of Mt. Everest, the highest mountain in the world.
But what about Gangkhar Puensum, in Bhutan?
This 7,570m high mountain is the highest mountain on Earth that has never been climbed!
No one has ever been to the top of Gangkhar Puensum.
There are not only new places to discover.
There are also new animals.
Scientists discover new animals all the time.
In 2011, during an expedition to the Philippines, scientists found hundreds of brand new animals!
Finally, there are some times when it is best to stop exploring.
There are some groups of people in the world who do not want to be found.
The people of the Sentinelese tribe live on North Sentinel Island in India.
They live away from people in cities and villages.
No one outside the Sentinelese tribe has ever met a Sentinelese person or seen a Sentinelese home.
The land of the Sentinelese tribe has never been explored.
But sometimes, it is best to stop exploring.
Sometimes, it is best to leave mysteries in peace!
Exercise
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