Background In Europe, the Farm to Fork Strategy provides ambitions for sustainable and circular food systems. However, what are the driving and uniting forces that keep systems sustainable? Scope and approach First, food systems are regarded as open thermodynamic systems, fuelled by solar energy, with seven building blocks: players, pieces, moves, playing fields, rules, wins, and time. Second, sustainable food systems are complex adaptive systems evolving in a melting zone, or safe and just operating space, between frozen states and chaos. Third, players (actors) and pieces (resources and products) are bound by 4 fundamental forces, as in physics, namely the strong, weak, electromagnetic energy, and gravitation forces. Key findings and conclusions A physics-based first-order approximation concept of sustainable food systems permits formulating relevant, future Food Science and Technology Developments. A network of food actors re-orient single food chains towards systems of diverse food products, resources, and diets. Their features are multi-functionality, resilience, adaptability, temporal and spatial flexibility regarding food handling. Their pathways are characterized by balancing patterns between frozen states and chaos, and not endless growth curves.