A century ago, science went quantum. To celebrate, physicists are throwing a global, year-long party.In 1925, quantum mechanics, the scientific theory that describes the unintuitive rules of physics on very small scales, began to crystallize in the minds of physicists. Beginning in that year, a series of monumental papers laid out the theorys framework. Quantum physics has since permeated a wide range of scientific disciplines explaining the periodic table, the lives and deaths of stars and more and enabled technologies from the laser to the smartphone.In honor of that century of progress, physicists are celebrating 2025 as the International Year of Quantum Science and Technology, as designated by the United Nations. The festivities kick off February 4 with an opening ceremony in Paris, and continue throughout the year with scientific conferences, public lectures and more, including QuantumFest, an event in March at the American Physical Society Global Physics Summit in Anaheim, Calif., featuring hands on activities and demonstrations.Beginning around 1900, a variety of experiments and theoretical advances began unveiling bits and pieces of the puzzling quantum realm. Then, a 1925 paper by German physicist Werner Heisenberg, followed shortly thereafter by papers from others including Austrian physicist Erwin Schrdinger, turned the hodgepodge of hints into a cohesive picture.We still use those equations that were published in 1925 and 26, says theoretical physicist Ana Mara Cetto of the National Autonomous University of Mexicos Institute of Physics in Mexico City. And they have led to a huge amount of theoretical results and experimental results and technological applications. The ensuing quantum revolution became the basis for much of modern physics.In those all-important years, says quantum physicist Smitha Vishveshwara of the University of Illinois Urbana-Champaign, the foundations of a completely different way of looking at nature became solidified.According to that new view of nature, matter absorbs energy in tiny, discrete packets, or quanta. And strangely, seemingly disconnected objects can be entangled, their properties correlated by an intangible link. Heisenbergs uncertainty principle, formulated in 1927, states that its impossible to precisely determine both the speed and momentum of an object. The weird quantum limbo known as superposition was famously illustrated in 1935 with Schrdingers cat, a scientific parable in which a hypothetical feline is both dead and alive. Over the past century, such oddities have permeated not only science but also the popular imagination.Science News spoke with Cetto and Vishveshwara, who are involved with this years celebration. Their responses have been edited for length and clarity.SN: Whats the importance of quantum physics today?Cetto: In these 100 years, quantum physics has become one of the major areas if not the major area of contemporary physics. It is difficult to find some area in physics or some problem in physics where quantum mechanics doesnt play a role, especially now that we are working with systems that are smaller and smaller in scale or shorter and shorter in time. Because that is where the quantum phenomena really show up.SN: What are the technological applications?Vishveshwara: Semiconductor technology, MRI, quantum computation, lasers all this comes from understanding quantum physics. You absolutely need to have an understanding of the atoms and elements and compounds at a quantum level to even create the basic circuit element that goes in your smartphone.Sponsor MessageSN: What are the goals of the International Year of Quantum Science and Technology?Vishveshwara: One is to really help raise public awareness of the wonders of quantum science and the way it affects our daily life. There are 60-plus countries behind it, so its really a global celebration. In addition to raising public awareness and bringing together different communities, I think its bringing people together from across the globe and across different walks of life in a way that I havent seen in my lifetime.SN: Quantum physics has a reputation for being mysterious is it?Vishveshwara: Its absolutely mysterious. I think thats part of its charm, because we all love mysteries. Already in popular culture, theres appeal. Now quantum is this ultracool word, where you have [Marvel character] Ant-Man going into the quantum realm.SN: What are some open questions that remain in quantum physics?Cetto: We are still lacking some basic elements that can get us the full picture. What is the physical cause of entanglement? What is the physical cause of the indeterminacy that is expressed in the Heisenberg [uncertainty principle]? Its not that it cannot be understood, because its not magic, its physics. We just have to work on it.