There is a particle that moves like a ghost, silently altering our understanding, and it is the neutrino. Walking under a quiet night sky, you suddenly hear a faint sound from afar-that is the arrival of a neutrino. Recently, scientists discovered a "ghost particle" with an energy so high it is astonishing in the deep waters of the Mediterranean. Its energy is 100 times that of previously observed neutrinos!

This ultra-high-energy neutrino, like a comet, travelled through thousands of meters of seawater and silently collided with the KM3NeT neutrino telescope that moment, the material inside the detector suddenly began to jump, producing the "Cherenkov radiation" we are familiar with. It is like tossing a stone into a calm lake, creating ripples on the surface of the water. Through this special radiation, scientists were able to capture the trace of this mysterious neutrino. Neutrinos are like invisible travellers, barely interacting with normal matter. Every day, billions of neutrinos pass through us silently. Like spirits flowing in the shadows, silently traversing the Earth and even the entire universe. Every second, about 100 billion neutrinos pass through every square centimetre, undeterred by obstacles, passing through walls and the Earth as though entering every space, yet without a sound. These seemingly fragile neutrinos are capable of undergoing a "transformation battle". They undergo "neutrino oscillations", meaning they change from one type to another during their propagation. This discovery not only overturns our understanding of neutrinos but also suggests they have a tiny mass. This small discovery seems to unveil a new veil of the universe, fueling scientists curiosity even more.

However, neutrinos are not easy to catch. They are like a hidden cheetah, always lurking in the most secretive places. Traditional detection methods can't easily capture their traces because the neutrino flow from the Sun always acts like noisy background interference, masking the faint signals of high-energy neutrinos. It is like trying to hear a faint sound in a noisy marketplace. To chase after these elusive particles, scientists had to invent more sensitive detection equipment. This is the moment for the KM3NeT neutrino telescope to "make its appearance". it is like the eye of the universe, hidden beneath the Mediterranean Sea, capable of capturing the deepest secrets of the cosmos. Unlike the IceCube detector located at the South Pole, KM3NeT chose the unique location of the Mediterranean, using seawater as the detection medium. The optical properties of seawater give it extremely high sensitivity when capturing neutrinos. The design of the KM3NeT telescope is like a giant "net", catching those "ghost particles" from distant interstellar space. However, capturing the trace of neutrinos is not an easy task.

Scientists rely on a special phenomenon called Cherenkov radiation. When a neutrino collides with molecules in seawater, secondary particles travel through the water faster than the speed of light, emitting unique blue light. This blue light is like lightning coming from the depths of the universe, revealing the moment of the neutrino's collision. By analyzing the intensity and angle of this light, scientists can infer the neutrino's energy and direction of motion, thus tracking its "shadow".

With this technology, it is like opening the door to a new world--those cosmic monsters that have always existed but were "invisible" to humans: black holes, supernovae, pulsars. However, with these technologies and devices. We can only glimpse a small corner, more mysterious events are happening and existing that we have not yet seen. To witness those scientists will need to keep working and create new detection equipment.

（Writer：Ciki）