One measured photon has roughly the energy of a falling ping-pong ball.
The Tibetan Plateau is a vast elevated plain almost five kilometers above sea level, sometimes called the Roof of the World. It is bordered to the south by the world’s highest mountain range and to the north by desert lands. It is one of the most isolated places on Earth.
But the extreme altitude makes it a useful place for scientists. In 1990, they built an observatory here to study the showers of subatomic particles that rain down from the upper atmosphere whenever it is hit by a high-energy cosmic ray. This work is better done at high altitude because there is less atmosphere to absorb the particles.