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China and Nepal, the countries that border Mount Everest, have announced that the world’s tallest mountain is 86 centimeters higher than the conventionally accepted measurement to date. Based on the data collected by the respective surveys, the two countries agreed on a new height: 8,848.86 meters. The common conclusion should sanction the end of a confrontation between China and Nepal that has been going on for years, and for reasons more political than scientific.
According to previous Chinese official measurements from 2005, Everest was 8,844.43 meters high, while according to Nepal it reached 8,848 meters. In 2010, China and Nepal agreed to take new measurements separately to establish the precise height of the mountain with more appropriate methods and with an agreement in 2019, they decided that they would report the survey results together. Among other things, various geologists and scientists estimated that the height of Everest may have changed due to the disastrous earthquake in Nepal in 2015.
The east, north and west sides of Everest belong to the Tibet Autonomous Region, which is part of China, while the south side, where most of the expeditions depart to reach the top, belongs to Nepal. For both countries, the possibility of participating in a mission to establish the height of the highest peak in the world was a source of pride, especially since all the measurements so far had been carried out by American, European or Indian research teams. At the same time, it was a scientific opportunity: the latest measurements had been made with less precise tools and methods than those that can be used today.
Nepal’s plan to define the timing and methodologies to be adopted for the new measurements of Mount Everest was launched in 2017. The first survey was carried out in 2018 and the analysis of the collected data began in 2019. The announcement of However, the survey results had been postponed due to the coronavirus pandemic, but also because, according to Nepalese times (Nepal’s main English-language newspaper), the Chinese team was still completing its measurements.
Nepal carried out its research in collaboration with the New Zealand government, which helped train the technicians by explaining how to install and manage the various GPS systems and how to read data and measurements.
To manage the surveys, the Nepalese exploration team used both traditional methods, such as trigonometric leveling, which allows calculating height differences with an accuracy many times less than one meter between two distant points up to a few kilometers, the distance between which is already known. and more innovative methods used in geodesy, which is the science that deals with studying the shape and size of the Earth, along with the field of gravity and its variations over time.
Among other things, the Nepalese team took into account factors such as Earth’s gravity and used radar and satellite systems to achieve even more accurate classification results. However, between May and June 2020, the Chinese team carried out further studies thanks to the Chinese constellation of BeiDou satellites and a series of exploration flights over the area around Everest; The data obtained were crossed with the survey instruments that the team of Chinese technicians had placed on the top of the mountain on May 28.
In the past, Nepalese and Chinese surveys had given different results because they used different measurement criteria, for example whether the height of the summit was calculated with or without the ice sheet on top. In the case of Everest, it is estimated that the ice sheet at the top is about 4 meters high, and its thickness also varies according to rainfall and wind (lately also due to global warming).
In addition, to calculate the height of Everest, China and Nepal used different places to establish the sea level, that is, the one from which the height of a mountain is calculated. China used the average level of the Yellow Sea, which lies between China and South Korea, as a starting point, while Nepal used a point in the Bay of Bengal, which separates India, Bangladesh and Burma. Despite this, the measurements of the two countries turned out to be very “close”, as had been anticipated. Times of Nepal.
Everest suffers an increase of about 1 centimeter per year due to the movement of tectonic plates. However, according to several geologists, Everest has collapsed in recent years, mainly due to the earthquake that killed more than 2,000 people in April 2015 and left many more missing. Christopher Pearson, a coach from the University of Otago (New Zealand) who collaborated with the Nepalese team in 2018, told the Nepalese times that the aftermath of the 2015 earthquake is only “the most recent contribution” to Everest’s continuing change due to tectonic activity.
The first measurement of the height of Mount Everest was that of the Great Trigonometric Study of India, an initiative launched in the mid-19th century with the aim of making precise scientific measurements in various parts of the Asian continent. In 1856 the height of the highest mountain in the world was calculated to be 8,840 meters, and the summit was named after the head of the Survey of India, George Everest, who, however, had nothing to do with the measurements. .
A century later, in 1955, a new expedition of the Survey of India concluded that the height of Everest was 8,848 meters. New Italian studies in 1992 had determined that the height of the mountain was 8,846 meters, while according to American estimates in 1999, Everest was 8,850 meters high.
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