Climbing Mt Everest

Ankit has wanted to climb Mt Everest since the day he found out it was the tallest mountain the world. One day, this desire becomes extra strong and he takes it up with Mummy.

Ankit: Mummy, Mt Everest is 5 miles tall, right?
Mummy: Yes, Ankit.
Ankit: Then why can we climb Mt Everest? We went to Rattlesnake Mountain. And that was 5 miles.
Mummy: Because Ankit, walking 5 miles is not same as climbing 5 miles.

Ankit looks confused. Mummy sees his confusion and decides to explain it to him using a glass and a string.

Mummy: Do you see this string? It is as tall as the glass is?
Ankit: Yes.
Mummy, wrapping the string around the glass: Now, when you climb a mountain, you don't go up and up. You go round and round like this. You see how you cannot get to the top by going the same distance?
Ankit: Yes.
Mummy: That is why you cannot climb Mt Everest by walking 5 miles.
Ankit: Yes. Also, if there was a string there, it would be much easier to climb.