Two isolated point particles of masses \(m_1\) and \(m_2\) carry opposite charges \(+Q\) and \(-q\), where \(Q > q\). The particles are released from an initial separation \(d\) with non-zero initial velocities directed straight toward each other, such that the system's total mechanical energy is negative (\(E < 0\), taking \(U(\infty) = 0\)). A student predicts that because the system is in a bound state, the particles will reach a non-zero distance of closest approach and turn around before colliding. Which of the following statements provides the correct physical explanation for why this prediction is incorrect?