A distant memory

Nothing can travel faster than light. When we look upon the night-time sky, the twinkling of the stars is but a distant memory, one that took years, decades, millennia to arrive. Is it any wonder, then, that nobody responded to Earth's radio broadcast? From the perspective of those who sent it, it was cast into the void more than ten years ago. Twenty-one more years would have to pass between each matched set of message and reply. Its meaning had not been easy to decipher for the people of Rán Beta, either. Extraordinary claims took time to verify, and this one - that the signal was intended as a greeting from an alien civilization that had emerged right next door - was an extraordinary claim indeed.

"They can't possibly know we're here," was a common counter-argument from astrophysicists. "Look here, at the part where they describe the radio telescope that they expect to receive our response. Mounted on their planet's surface, incapable of detecting the existence of other worlds - I doubt these people can even travel into space. Surely, we would have noticed if they could." The scientific community had not noticed anything unusual about Earth before its greeting came blasting through, because they kind of hadn't been paying attention. Once they'd actually aimed their telescope array in the right direction, they noticed a lot of unnatural radio signals that definitely hadn't been there a couple centuries ago.

One of the most prominent philosophers of Rán Beta had other concerns: "To announce your presence like this is recklessly optimistic. The people of Earth must be a peaceful civilization without war or oppression, to be so unafraid of what we could do to them and to the only planet they have. To respond to this message at all would irrevocably harm their society. The only ethical thing to do, is to not reply."

"Right, so we should greet them in person!" said the scientific community.

"That's the exact opposite of what I just-"

"Yes, this is the best idea! That way, if our response somehow causes them to turn evil, we will actually be able to notice the misinterpretation and tell them that that's not how we meant it. Now let's go meet some cool aliens!"

So, plans were drafted for the immediate construction of a hyperspace tunnel that would connect the two planets in time and space, and these were submitted to the government of the Interplanetary Alliance. After some bureaucracy (and arguments about whether it was economically viable to do this), construction started. Even with the assistance of more than just one world, it would take a while, but it was a short enough time that many people would see its completion in their own lifetime. And if it turned out that by the time it was done, Earth civilization had already wiped itself out in a robot apocalypse (as civilizations were wont to do), the tunnel could still find use as a shortcut between Rán Beta and some other place.

From Earth's perspective, humanity had spent a couple of decades scouring the universe for intelligent life and finding nothing, until suddenly a big alien spaceship appeared really close to Earth and started broadcasting radio signals. Their memories of the original greeting might have faded with time, but the Internet hadn't forgotten. The people of Earth knew exactly what they'd done, and what the response meant, because it held enough of a resemblance to the original.

"Hello, Earth! Nice to meet you :)"