HIP Quiz 2025

A linear accelerator is a long, straight device in which particles gain speed through carefully timed electromagnetic fields. These fields alternate in rhythm, giving charged particles a sequence of pushes in the same way a child on a swing gains more height with each well-timed push. Step by step the particle’s velocity increases until it reaches enormous energies. Linear accelerators are central tools in particle physics, where scientists explore the building blocks of matter and the fundamental forces of nature. They also have practical applications in medicine, such as in radiotherapy machines that treat cancer. At the Observatory a simple demonstration uses a metal ball that is accelerated by small magnets along a track. The ball never comes close to the speed of light, yet the principle is the same: successive kicks add up to high speed. This playful experiment helps the audience imagine how real accelerators work and why they are so crucial for science.

The Large Hadron Collider (LHC) is the world’s largest particle accelerator, a gigantic 27-kilometre ring near Geneva. Before reaching the main machine, protons are boosted by smaller accelerators such as the PS and SPS, preparing them for the ultra-energetic collisions ahead. Inside the LHC two proton beams travel in opposite directions at nearly the speed of light and meet at four huge detectors, where millions of collisions take place every second. These violent encounters create a wide variety of particles, many of which exist only for a tiny fraction of a second but reveal deep truths about the laws of nature. In 2012 the LHC enabled the discovery of the Higgs boson, one of the landmark achievements of modern physics. The simple computer game, where the task is to steer beams so they collide, gives visitors a taste of how extremely difficult it is to keep real proton beams on course. Even the smallest misalignment would mean no collisions at all, wasting the opportunity for discovery.

Researchers use synthetic diamonds as radiation detectors, because diamond is extremely resistant to radiation and produces clear electronic signals. Metal electrodes are deposited on the surfaces, collecting the charge created by passing particles. When these diamonds are examined with light microscopes, internal defects become visible. These imperfections often look surprisingly artistic: tiny cracks or electrical discharges resemble a supernova, a starry sky or even a flower. The exhibition images are genuine scientific data, yet they also evoke aesthetic impressions. Defects can arise from irregularities in the crystal lattice or from damage to the electrode during measurements. By analysing them, scientists learn about both the strengths and weaknesses of the material, while visitors are invited to see science from a new angle – at the boundary between knowledge and art.

A cloud chamber is a classic device that makes invisible radiation visible. Inside the chamber the gas is kept supersaturated so that even the smallest ionization causes vapour to condense. As a particle passes through, it leaves a delicate trail behind, as if drawing a line in mist. Different particles produce characteristic shapes: alpha particles leave short, thick tracks, light electrons bend and curl, while protons create long, straight traces. In this way it becomes possible to distinguish what kind of particle has been observed. The cloud chamber was an essential instrument in the early days of particle physics, leading to the discovery of several new particles during the 20th century. Today it serves mainly as an educational tool and public demonstration, but the principle remains unchanged: invisible particles are revealed as elegant patterns that can be followed with the naked eye.

The research of the very early universe is difficult, since we are trying to look back to the first fraction of a second after the Big Bang. Cosmologists try to model the phenomena by using e.g. simulations that run on powerful supercomputers. One interesting question concerns the electroweak phase transition (electromagnetic and weak force break apart) that may have happened during this primordial epoch and the new answers it may offer us about the early stages of our universe. Although nobody can observe the very first instants directly, computational models provide a way to test theoretical models and compare them with upcoming data from future experiments like LISA.

Surprisingly, a simple device for detecting particles can be built from an ordinary aluminium beverage can. Inside the can a suitable gas is introduced, with a thin wire serving as an electrode. When ionizing radiation passes through, it knocks electrons off gas atoms. Their movement creates a tiny electrical pulse that can be amplified and measured. The principle is known as a gaseous proportional counter, and the same idea underlies many professional radiation detectors. The can detector therefore demonstrates how invisible particle interactions in the air can be turned into visible signals. Although the construction is basic, the physics is identical to that used in the sophisticated detectors at CERN. Visitors can thus appreciate how even everyday materials can be transformed into real scientific instruments that reveal the hidden world of radiation.

Semiconductor particle detectors are central to modern physics. When a charged particle passes through silicon, it breaks bonds and creates electron–hole pairs. These are collected by an electric field, producing a pulse that reveals the particle’s energy and path. Such detectors are extremely precise: at CERN they can pinpoint a particle’s position to a fraction of a millimetre and trace what happens in collisions. Semiconductor detectors have replaced many older technologies thanks to their speed, compactness and reliability. They are also used outside physics, in medical imaging and in security systems such as airport scanners. Although the underlying principle is straightforward, it enables the construction of highly complex instruments that open a window into the deepest structure of matter.

Dark matter is a mysterious component of the universe: it emits no light and cannot be seen with telescopes, yet its gravity binds galaxies together and shapes the large-scale structure of the cosmos. Without dark matter, galaxies would spin apart instead of holding together. Studies suggest that about one quarter of the universe’s total energy content is dark matter, though its particles remain unknown. Theories propose candidates such as WIMPs or axions. Cosmological observations, from maps of the cosmic microwave background to the motions of galaxies, provide strong evidence for its presence. Experiments at CERN and elsewhere are designed to search for dark matter particles directly. Visitors are invited to reflect on how much of reality is still hidden and how future discoveries may transform our view of the structure of the universe.