"For the future," says the astronomer. "Humanity always needs challenges, horizons, adversity, to be constantly striving for the future. We had plans for the future. We went to the Moon and we were going to found a colony there. We were going to go to Mars, and found a colony there too. We were going to colonise Europa, and Titan, and maybe others. We were going to capture and mine the asteroids, build space elevators, build ark ships and go to other star systems. We need space... so that we can study, and learn more about the universe and discover new science. We could be like you, flying faster than light-- we know it's possible now! We could gain that much power. If you only gave us the time. We could colonise the galaxy and the universe."
"But you haven't."
The astronomer lowers his gaze from the growing ink blot in the sky and looks towards the horizon. Bright city lights. "To survive," he says. "One world cannot protect us forever. Humanity is vulnerable, living on a single unprotected rock. We need to be insured in case of asteroid impacts, or gamma ray bursts from space. We need to diversify genetically, to adapt to new environments and live on new worlds and look at the universe through new eyes. There's no other way to survive. You're taking away billions of years of potential future."
"No, we aren't."
He tries to stop shaking. "We need... something to shoot for. It's the only reason we ever built anything. It's the only reason we have mathematics, the only reason we have science. Because we wanted to understand the sky. We need light. We need stars to follow. We need inspiration."
Bright city lights. Millions of people who never even looked at the stars.
The voice says, "With the Moon and stars and planets we provided you with boundless opportunities. We gave you gifts. But you have shown no inclination to take advantage of them. Thus, the gifts are worthless to you, and we are giving them to somebody else."
The planets are all long gone. The inkblot finally closes overhead and the last star winks out. The gibbous Moon remains shining balefully down on the world for a tense and hopeful minute, but then, in an eyeblink, is swallowed up by one final event horizon, and spirited away.
Left in utter darkness, the former astronomer tries and fails to deal rationally with his loss, and his isolation from the human race who, as the voice rightly tried to tell him, has really lost nothing.