No, it is not accurate to say that quantum mechanics requires the act of observation to determine definite properties. This statement is a simplified and often misunderstood interpretation of certain aspects of quantum theory.
In quantum mechanics, the behavior of particles and systems is described by mathematical equations called wavefunctions. These wavefunctions contain information about the probabilities of different outcomes when a measurement is made on a quantum system. According to the Copenhagen interpretation of quantum mechanics, which is one of several interpretations, the act of measurement causes the wavefunction to "collapse" into one of the possible states, yielding a definite outcome.
However, it is crucial to understand that this collapse of the wavefunction is not dependent on conscious observation or human interaction. Instead, it is any interaction between the quantum system and its environment that can cause this collapse. For example, a photon colliding with a particle or a particle interacting with a measuring apparatus can trigger the collapse.
The idea that quantum systems exist in a superposition of states until observed is often referred to as the "observer effect" or the "measurement problem." It is an area of ongoing debate and discussion among physicists, and various interpretations exist to explain these phenomena, such as the Many-Worlds interpretation, the pilot wave theory, and the objective collapse theories.
Ultimately, the mathematics of quantum mechanics accurately describes the behavior of microscopic particles and systems, and experimental observations support its predictions. However, the interpretation and philosophical implications of quantum theory continue to be subjects of active research and scientific inquiry.