Yes, measuring or observing a quantum system has a fundamental effect on quantum physics. This effect is commonly known as the "measurement problem" or the "observer effect." The measurement process in quantum mechanics causes the wavefunction, which describes the quantum state of a system, to collapse into a particular eigenstate corresponding to the measured value.
According to the principles of quantum mechanics, prior to measurement, a quantum system exists in a superposition of multiple possible states. The act of measurement forces the system to "choose" one particular state out of the superposition. This collapse of the wavefunction is a non-reversible process and introduces a fundamental indeterminacy into quantum physics.
Furthermore, the measurement process is probabilistic in nature. The outcome of a measurement is not deterministically predictable, but rather it follows statistical probabilities governed by the wavefunction of the system. The probabilities of different measurement outcomes are given by the squared magnitudes of the coefficients in the wavefunction expansion.
The measurement process and its effects are at the core of many intriguing aspects of quantum mechanics, such as the uncertainty principle, entanglement, and the phenomenon of quantum superposition. These effects have been experimentally verified through numerous experiments in the field of quantum physics and have profound implications for our understanding of the nature of reality at the microscopic scale.