Starplex

"But, as I said, you — l — we are a special case of immortality."

"How so ?"

"There are, in fact, only three older human beings than me in the entire universe. Apparently, I had a — what do you call it? — an 'in' that got me the immortality treatments early on."

"Rissa was working on senescence research; I assume she ended up being codeveloper of the immortality technique."

"Ah, that must have been it," said Glass.

"You don't remember?"

"No — and that's the whole problem. You see, when they first invented immortality, it worked by allowing cells to divide an infinite number of times, instead of succumbing to preprogrammed cell death."

"The Hayflick limit," said Keith, having learned all about it in conversations with Rissa.

"Pardon ?" "The Hayflick limit. The phenomenon that limits the number of times a cell can divide."

"Ah, yes," said Glass. "Well, they overcame that. And they overcame the old, natural limitation that said you were born with a finite quantity of brain cells, and that those cells were not normally replaced. One of the keys to immortality was to let the brain constantly create new cells as the old ones wore out, so-"

"So if the cells are replaced," said Keith, eyes growing wide, "then the memories stored by the original cells get lost."

Glass nodded his smooth head. "Precisely. Of course, now we offload old memories into lepton matrices. We can remember an infinite amount of material I don't just have access to millions of books, I actually remember the contents of millions of books that I've read over the years.

But I became an immortal before such offloading existed.

My early memories — everything from my first couple of centuries of life — is gone."

"One of my best friends," said Keith, "is an Ib named Rhombus. Ibs die when their early memories get wiped out — new memories overwrite their basic autonomous routines, killing them."

Glass nodded. "There's a certain elegance to that," he said. "It's very difficult to live without knowing who one is, without remembering one's own past."

"That's why you were disappointed that I'm only forty-six."

"Exactly. It means there's still a century and a half of my life that you can't tell me about. Perhaps someday, I'll locate another version of me, from — what would that be? — from about the year 2250 in your calendar." He paused. "Still, you remember the most crucial parts.

You remember my physical childhood, you remember my parents.

Until I spoke to you, I wasn't even sure that I'd had biological parents. You remember my first love. All of that has been gone from me for so incredibly long. And yet, those experiences shaped how I behave, set down the patterns of my personality, the core neural nets of my mind, the fundamentals of Who I am." Glass paused. "I have wondered for mille

There had been a horizon in my past, a curve beyond which I could not see. You have taken that away. What you have given me is beyond price." Glass paused, then his tone grew lighter. "I thank you from the bottom of my infinitely regenerating heart."

Keith laughed, like a yelping seal, and the other Keith laughed too, like wind chimes, and then they both laughed at the sound the other had made.

"I'm afraid it's time for you to go home," said Glass. Keith nodded.

Glass was silent for a moment, then: "I have refrained from giving you advice, Keith. It is not my place to do so, and, frankly, there are ten billion years between us. We are, in many ways, different people.

What is right for me, now, at this stage of life, may not be right for you. But I owe you — for what you have given me, I owe you enormously, and I would like to repay you with a small suggestion."

Keith tilted his head, waited.

Glass spread his transparent arms. "I have seen the ebb and tide of human sexual morality over the eons, Keith. I've seen sex given as freely as a smile, and I've seen it guarded as though it were more precious than peace. I've known people who have been celibate for a billion years, 'and I've know others have had more than a million partners. I've seen sex between members of different species from the same world, and between those who evolved on different worlds. Some people I know have removed their genitals altogether to avoid the issue of sex. Others have become true hermaphrodites, capable of procreative sex with themselves.

Others still have switched genders — I have a friend who changes from male to female every thousand years, like clockwork. There have been times when humans have embraced homosexuality, and heterosexuality, and incest, and multiple concurrent spouses, and prostitution, and bestiality, and sadomasochism, and there have been times when all of those have been abjured. I have seen marriage contracts with expiration dates, and I have seen marriages last five billion years.

And you, my friend, will live long enough to see all these things, too.

But through all of it, there is one constant for people of conscience, for people like you and me: if you hurt someone you care about, there is guilt."

Glass dipped his head. "I do not remember Clarissa. I do not remember her at all. I have no idea what happened to her. If she, too, became an immortal, then perhaps she still exists, and perhaps I can find her.

I have loved a thousand other humans over the years; a paltry number by many people's standards, but sufficient for me. But there is no doubt that Rissa must have been very, very special to us; that's apparent in the way you speak of her."

Glass paused, and Keith had the eerie feeling that eyes — invisible in that smooth transparent egg of a head — were seeking out his own, seeking the truth behind them. "I can read you, Keith. When you told me earlier to move along, to pick another topic, it was obvious what you were hiding, what you have been contemplating." A beat of silence; even the forest simulacrum around them held its peace. "Don't hurt her, Keith. You will only hurt yourself."

"That's the advice?" asked Keith.

Glass lifted his shoulders slightly. "That's it."

Keith was quiet for a time. Then: "How will I remember that? You said you were going to wipe my memories of this meeting."

"I will leave that thought intact. You will indeed have no memory of me, and you'll just think it came from yourself — which, of course, it did, in a way."

Keith thought for a time about what the appropriate reply was.

Finally, he said, "Thank you."

Glass nodded. And then, sadly, he said, "It's time for you to go."

There was an awkward moment during which they stood and looked at each other. 'Keith started to extend his hand, but then let it drop to his side. Then, after a second of hesitation, he surged forward, and hugged Glass. To his astonishment, the transparent man felt soft and warm. The embrace lasted only a few seconds.

"Perhaps someday we'll meet again," said Keith, taking a step back now.

"If you ever feel like popping through to the twenty-first century for a visit…"

"Perhaps I will. We are about to start something very, very big here.

I told you at the outset that the fate of the universe is in question, and I — meaning you, too, of course — have a key role to play in that. I gave up being a sociologist ages ago. As you might guess, I've had thousands of careers over the mille

"Just remember our full name, for God's sake," said Keith. "I'm listed in the Commonwealth directory, but you'll never find me again if you forget."