The year is 2075. Twenty-one years earlier, SETI detected a message from an alien civilization. It took almost a year to decipher it. SETI scientists then sent a reply message to planet X, located some 10 light-years from Earth. Now, twenty years later, they have received a reply.
The aliens have asked many questions about the environment of Earth and about its inhabitants. It is clear that the aliens are advanced, but it is unclear how much of a scientific superiority they have. An international conference has been organized to decide how to respond to the aliens' questions.
Jupiter Scientific has been contacted in an advisory role. World leaders are quite concerned that the aliens may attempt to travel to Earth if they have sufficiently powerful space-travel technology. What can be done to discourage this, since such a visit is not guaranteed to be friendly? Perhaps the aliens are looking for another planet to colonize.
Jupiter Scientific has devised a scheme to convince the aliens that we are extremely scientifically advanced. A series of spacecraft should be launched in the coming year so as to span the entire solar system along a line perpendicular to the direction of planet X.
When in place, the craft at one end of the solar system will begin transmitting the first part of the reply message. Soon after, the next craft will send out the next part of the message. The process will continue along the line until the last craft, at the opposite end of the solar system from the first, finishes the transmission.
The timing of the emissions will be such as to create the impression that the message is coming from a single spaceship traveling at slightly faster than the speed of light. The content of the message is to be a reply to the aliens' questions ending with "We are an advanced civilization, but have no intentions of visiting your planet; our solar system is sufficient for our needs. We respect the right for all life to develop independently and in peace."
"A visit from us to your planet might introduce a deadly microbial infection that your immune system will not be able to fend off. Likewise, a visit from you might be unhealthy for us. Please do not attempt to travel to Earth. We wish you the best for your civilization."
Jupiter Scientific believes that the aliens, seeing that we have achieved near-light-speed travel, will not dare visit Earth even if they have the capability. If SETI receives a reply in another twenty years, we will respond by proposing a non-aggression pact, which would be the first of its kind between life forms from different planets.