Fields are a fundamental concept in physics that describe the interactions between particles or objects in space. According to our current understanding, fields do exist independently of the presence of particles. In classical physics, fields are considered continuous and spread throughout space.
In the context of quantum mechanics, the concept of fields becomes intertwined with the behavior of particles. Quantum field theory (QFT) is the framework that describes the behavior of both particles and fields. In this theory, particles are understood as excitations or quantized vibrations in their corresponding fields.
The statement you mentioned, about particles acting like they have well-defined positions only when observed, refers to the concept of wave-particle duality. In quantum mechanics, particles can exhibit both wave-like and particle-like properties, depending on how they are observed or measured. The act of measurement or observation can indeed affect the behavior of particles.
However, it's important to note that the existence of fields is not dependent on the act of observation. Fields exist and interact with particles regardless of whether they are being measured or observed. The observation affects the properties of the particles themselves, revealing certain aspects of their behavior, but the fields are still present and interacting with the particles throughout.
In summary, fields are considered fundamental entities in physics, and they are not dependent on the act of observation. While the behavior of particles can be influenced by observation, the existence of fields is a separate concept that describes the interactions between particles and their surroundings.