Two spaceships 1 and 2 are heading towards the Earth (figure), moving along the same straight line at the same speeds. At some point in time, each ship and the Earth send each other short light signals (ship 1 sends a signal to ship 2 and the Earth, ship 2 sends a signal to ship 1 and the Earth, and the Earth sends a signal to ships 1 and 2). It is known that all signals are sent simultaneously in the reference frame associated with the Earth. It turned out that the time interval between received signals according to the onboard clock

Short solution. Format gif