Imagine stepping into a machine, pressing a few buttons, and emerging in a different century. What once existed purely in the imagination of science fiction authors is now increasingly entering the domain of scientific possibility. The idea of time travel—moving forward or backward through time—has captured human curiosity for generations. In tandem, the mysterious concept of dark energy—an unseen force accelerating the expansion of the universe—has become one of the most important puzzles in modern physics. It’s no coincidence that conversations about time travel and dark energy have surged during this symbolic year. In January 2025, a transatlantic consortium of European and American physicists announced a collaborative quantum simulation project (total cost USD 5.5 million) aiming to model dark energy using next-generation quantum processors—an exemplar of the growing nexus between quantum mechanics and cosmological inquiry. As 2025 has been formally designated the International Year of Quantum Science (IYQS), the global scientific gaze is now firmly affixed upon the quantum arena, which may well harbour the elusive resolutions to some of the universe’s most profound ontological riddles. 

Time travel has mesmerised both the public and physicists, but modern science suggests that it may be theoretically possible. Albert Einstein’s general theory of relativity (1915) remoulded our understanding of time and space by showing that time is not a fixed constant. Instead, it can stretch or compress depending on gravity and velocity. This led to the phenomenon of time dilation, which is now a proven effect. Astronauts on the International Space Station age just a little bit more slowly than those on Earth due to their speed and distance from Earth’s gravity. More exotic ideas come from concepts such as wormholes—hypothetical tunnels in space-time that could potentially connect two different points in time or space. These ideas are based on solutions to Einstein’s equations but remain highly speculative due to stability issues and the need for exotic matter with negative energy.