Everest: The world's tallest mountain... or is it?

Some things in life are certain: Everest is the world's highest mountain... the sun always rises in the east... and if you drop your brekkie slice of toast on the floor, it's sure to land with the buttered side down.

But now a team of experts are being sent to check one of those certainties - just how tall is Mount Everest?

Officially, the summit of Everest stands at 8,848 metres in height, a measurement first recorded by an Indian survey 65 years ago in 1954.

Now four land surveyors from Nepal, who have spent two years training for their mission, have begun the treacherous climb to the peak of Mount Everest to check whether that measurement really is correct.

They'll use advanced equipment to try and find the true height of the pinnacle.

Everest sits on the border of Nepal and China, but the two countries can't agree on its height.

Chinese experts think that only the rock should be counted in the measurement, while Nepalese scientists say the snow should also be included.

And if that wasn't enough of a complication, many think that a powerful earthquake in Nepal in 2015 could have knocked some height off the peak.

Others argue that Mount Everest might have grown because of the shifting tectonic plates it sits on.

Whether or not this mission to the top helps geographers to agree a definite answer is yet to be seen. But it definitely sounds like a very exciting project.