A student models the journey of a deep-space probe that takes exactly two years. The probe travels directly away from an observer at a constant speed of 1.5 × 10⁷ m s^-1. The student predicts that a clock stationary relative to the observer on Earth will record a time at least three days longer than an identical clock on the probe.

Comment on the student's prediction. Support your answer with a time dilation calculation.

In practice, the gravitational field of a nearby star affects the probe's trajectory, causing it to deviate from a straight-line path. Explain why this means that the theory of special relativity cannot be applied to this journey.