Imagine a scenario where a spacecraft maintains a steady velocity, moving horizontally to the right relative to Earth. Within this spacecraft, an observer positioned at its center observes two laser beams - one green, on the left side, and the other blue, on the right side - striking the endpoints of the spacecraft simultaneously as shown in the figure below. Concurrently, an observer stationed on Earth observes the same two events. From the perspective of the Earth-based observer, which of the two events occurred first?