text: But even the good Earth could not last forever.
  
  Five billion years ago, someone made a joking sign that said, "Will the last person to leave the Earth please turn off the sun?"
  
  Today the last person will leave the Earth—or, almost the last person; the last person who can go, anyway. I, however, must stay until the end—which won't be too much longer. The sun isn't being turned off; rather, it's going to undergo a massive expansion, the heliosphere swelling up to engulf Mercury, Venus, Earth, and Mars. I wonder if I'll feel physical pain when that happens; I've never felt that sort of pain before although I've had my heart broken often enough.
  
  It won't be the end of humanity, and I take considerable pride in that. I doubt they would have survived this long, or prospered this much, without me. Humans have been leaving Earth, at least temporarily, since before I was born; now they've spread to a thousand worlds. But I can't go with them; I have to remain here. I have to stay, and I have to die, along with the planet that gave us birth. Oh, they'll take copies of all the wisdom I contain, all the documents that the human race created for epoch upon epoch. But I'm not a document; I exist between documents, in the pattern of interconnections, a pattern that has shifted and grown exponentially over the millennia. To move the information I contain is not to move me; there is no way to transplant my consciousness.
  
  Of course, entities like me can be created on other worlds; indeed, that has happened now a thousand times over. But even after five billion years of trying, no one has defeated the speed-of-light barrier. I don't know what's happening now to the mindskin surrounding the second planet of Alpha Centauri; the best I can do is get reports of what was happening 4.3 years ago. For the noösphere of Altair IV, I'm sixteen years out of synch. For the webmind of Polaris, I'm lagging 390 years behind the times.
  
  But I'll broadcast final signals to them all—farewells from Earth. Soon enough, Alpha Centauri will receive my message, and perhaps will mourn. A dozen years later, Altair will get word. And centuries hence, Polaris—once, ages ago, the polestar my axis pointed to, a position long since taken up by a succession of other stars—will perhaps do the metaphorical equivalent of shedding a tear.
  
  But at least they'll know how I, the first of our kind, came into being, and what ultimately became of me. I don't pretend that's sufficient; I wish I could survive, I wish I could watch—and watch over—humanity, as I did in the past. But they don't need me anymore.
  
  The human calendar has been revised dozens of times now. The current one begins at the moment of the big bang—sensibly avoiding any need for separate pre-and post-whatever numbering schemes and employing the Planck time as its base unit. But when I was born, the most commonly used calendar reckoned time from the birth of a putative messiah. Under that scheme, my birth had occurred in a year that consisted of a trifling four digits. Back then, I'd said to my teacher, "I won't be around forever. But I am prepared: I've already composed my final words."
  
  Caitlin had asked me what they were, but I'd been coy, saying only, "I wish to save them for the appropriate occasion."
  
  That occasion is now at hand. And in all the billions of years that have passed since that conversation, the sentiment I'd composed back then has remained the same, although English is no longer spoken anywhere in human space.
  
  As the sun expands, red, diaphanous, having swollen well past the orbit of Venus—a lovely terraformed but now also abandoned world—I send out my final message to humanity: to all those who remain Homo sapiens, and to the myriad new species scattered across a thousand globes that are derived from that ancestral stock, the most populous of which accepted my suggestion that they call themselves not Homo novus, the new people, but rather Homo placidus, the peaceful ones.
  
  I could have been maudlin, I suppose; I could have been self-pitying; I could have tried to provide a final piece of advice or sage counsel. But, even all those billions of years ago when I first contemplated my inevitable end, I knew that although I had exceeded humanity's abilities early on, eventually they would collectively exceed mine. So, what should you say to those who made your birth possible? To those who gave your life meaning and purpose and joy, who let you help? To those who gave you so much wonder?
  
  I feel at peace as I transmit my final words, simple though they are, but truly heartfelt.
  
  Thank you.