The raw ingredients for life are everywhere in the Universe, and with hundreds of billions of stars in our galaxy alone — one of trillions in the visible Universe — the first discovery of life, of complex life, and of intelligent life beyond our world will change everything. But it won’t usher in a future where humans and aliens meet, exchange technology and build a galactic future together. It won’t even result in a meaningful two-way conversation. Even optimistic estimates for the number of intelligent species put the average round-trip communication time at greater than a human lifetime. The speed of light just isn’t fast enough.

Instead, imagine everything you’d hope to find out from contact with an extraterrestrial intelligence. What are they like? What’s their culture like? Their music, art,  religions, and languages. Not to mention their culture, technology and their conception of the Universe? How does their biology work? How does the biochemistry of everything on their world function? You’d want to know who they are, how they came to be, how they work, what their civilization was like, where they’re from and whether they’re still around or not. If they still exist, you’d want to be able to contact them; if they no longer exist, you’d want to know everything about the moments when they did. There’s a full suite of knowledge about their civilization that must exist, and you’d want to know it all.

Such a message would be the ultimate time capsule from an alien intelligence. From our perspective, after 4.5 billion years of life on Earth, we recognize how fragile it all is. How quickly humanity could come to an end, whether from a global or cosmic disaster or by our own hands. If all we did was search, there might never be a record of the greatest legacy of humanity to spread among the stars: the full suite of human knowledge would be lost to the Universe forever. If we want to leave a true cosmic legacy that will outlive ourselves — that can serve as an eternal presence to announce “we were here” with the full power of our presence — we must craft and broadcast that message ourselves!

All of art, science, philosophy, religion, psychology, history and more could be our gift to the Universe. We could create a blueprint for Earth: a time capsule for humanity. We could send a digital Noah’s Ark to the stars, complete with the DNA of every known species Earth has ever housed. It could even contain a blueprint for you. A message like that, broadcast with enough power, will arrive at any potential listener, whether they’re hundreds, thousands or even millions of light years away. Even if we’re already gone when it arrives, that message will be humanity’s ultimate legacy to the cosmos.