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by Miriam English

11. memory

Janelle was using her computer. It displayed the scenery of her own virtual world -- one of those connected via the peer to peer universe. Her avatar was standing motionless in the middle of a small clearing among the trees and shrubs of Janelle's little forest. Myra's avatar was moving about on the other side creating more vegetation.

"Dammit!" Janelle was infuriated.

"A problem?" Myra's avatar stopped and looked in the direction of Janelle's.

"One of my drives just showed an error. Even with regular backups I always lose stuff during a drive failure."

"Be thankful for small blessings. At least we don't have to rely on mechanical hard drives like people did in the past. They generally failed catastrophically, and often without warning."

"Solid state drives are only a small improvement though." Janelle rubbed her face in frustration. "It is the lack of redundancy that bugs me. I could store everything in multiple locations and avoid some of the problem, but they're so expensive and it doubles the cost... or trebles the cost if you want a safer, error-correcting system, where two uncorrupted locations out-vote the failed one. And even then they only have a limited lifetime anyway -- it still has to fail, in a decade or less."

"True. A permanent solution would be wonderful."

Janelle said, "It bugs me that we don't have something like static RAM."

"That needs a battery to keep its data and the circuits are actually much more complex," Myra reminded her, "Each memory cell is a tiny bistable flip-flop."

"Yeah." Janelle sighed. "I remember reading something about that. Even so, surely we could use capacitors to hold enough charge while switched off, and miniaturisation is so good at stuffing more and more circuitry on a chip I don't see why we can't have cheap, high-capacity static RAM... even if it doesn't hold as much as flash RAM and certainly not as much as memristors, but at least it lasts, unlike flash RAM and memristors."

"--So long as you have current on it," said Myra. "Lose that and you lose everything."

Janelle was still frustrated. "And why can't we build in three dimensions yet, instead of on flat wafers?"

After a few minutes of silence Janelle asked, "Ummm... are you not saying anything because you don't know the answer or because you want me to stop being negative?"

Myra's avatar smiled, "Neither. There are genuine problems in using present day chip technology in more than a few layers. And your dissatisfaction with memory devices is warranted. I was quiet because I was trying to connect a couple of odd bits of information that had occurred to me before passing them on to you."

"Don't worry about connecting. Just tell me what you're thinking."

"Recently one of my selves began working with a biologist named Neil, who was using some interesting methods of growing sponges."

"Sponges? How does that relate?" Janelle was lost.

"Uh, that's what I was trying to connect. When you think of sponge, you probably think of the plastic foam things people use in the bath or shower, right?"

"Yeah," Janelle said.

"Well, biological sponges are strange animals. They don't have any centralised organs and are more like colonies of individuals than multicellular animals, even though they are actually pretty well organised."

"What do you mean that they're more like colonies?"

"In 1907 a guy named... ummm... H. V. Wilson wrote about a weird experiment he did. He pushed a sponge through a sieve to divide it into its individual cells. Afterward the most amazing thing happened. Left in a container of water, the cells gradually moved together and reassembled themselves into a sponge."

"Wow. You're right, that is weird. What was he thinking? 'Hey, today I'll take this animal and push it through a sieve.' Huh."

Myra's avatar smiled. "He probably had some idea it might rebuild. Perhaps he'd seen sponges survive being badly damaged and reconstructing themselves. Noticing they don't have separate organs, maybe he wondered what the limit of repair was. Pushing though a sieve is pretty extreme, of course, but perhaps that was the point -- the ultimate way of tearing apart the whole sponge without killing the individual cells. Only some sponges can recover from this, though."

"So... your point..."

"I don't really have a point... I'm just feeling my way to a half-perceived connection."

"Okay, continuing..."

"Yes... The cells of most sponges secrete little spikes of mineral as a kind of skeleton. Some use calcium carbonate, but many, especially the deep-sea, glass sponges, use silica."

"Silica? Silicon dioxide. Like... sand. Quartz. Huh." Janelle said, "Surprising that such an inert material could be used by animals for building."

"Yes, isn't it. But listen to this: It turns out that some of these silica fibres are superior to the best light-fibers that people have been able to make, and the sponges make them in ordinary seawater at normal temperatures, instead of the furnaces and extreme chemical conditions technologists use. And some of them have perfect little lenses on the end."

"Wow. That's so cool. So is that what this guy Neil is working on?"

"Not directly. He's more interested in how the sponges organise. Oh, and I think we have the connection here. Can you see it?"

Janelle thought for a moment. "Earlier, we were talking about how flawed computer long-term storage is. Are you thinking that sponges could be made to grow optical switches that could be used as memory elements?"

"Wow. Nice leap Janelle."

"Thank you, but you really led the way." Janelle got caught up in a further thought, then said, "Myra, we were talking about long-term storage. But we're back to the same old problem. After you kill the sponge and harvest the tiny spikes you'd still need something like the photosensitive dye that writeable DVDs use to save data, which only lasts several years, and who knows how you'd address them..."

"Who said anything about killing the sponge?"

"But we need something long-term. Seriously, how long could a crummy sponge live?"

"Estimates of the age of some deep-sea sponges puts their ages at ten or twenty thousand years."

"Holy cow!" Janelle laughed. "Well, I guess that's long term enough." Then she was struck by a sobering thought. "Gee, that means some sponges alive today began their lives before the dawn of human civilisation."

"Actually it's even more amazing than that. Sponges were probably the first multicellular animals, or at least among the first... about five hundred million years ago. And there is some indication that sponges may be effectively immortal because they can propagate asexually. Though they can also have sex."

"So some sponges could be hundreds of million of years old?"

Mira's avatar nodded.

When Janelle spoke next, it was with some awe. "Kind of boggles the mind, doesn't it. Humans have been around for just an instant compared to these patient things that just sit and grow -- no brain, no senses, just sitting and feeding."

"Actually they do have senses. Some of the deep-sea sponges can pass electrical messages between their cells. And the individual cells of all sponges do react to their surroundings. But you're right that they don't seem to have anything like a brain."

Janelle was suddenly crisply alert again. "So, back on topic. How do we try out some things with sponges?"

"Odette, my sister who is helping Neil, says that she's asked him to send us some samples of his sponge. We should have it tomorrow. It only has to travel from Townsville -- he works at James Cook University."

"So this guy, Neil, is studying sponges' shapes?"

"Not quite, he's working out how they grow into their shapes. He's found several hormones that sponge cells release that affects how neighboring cells grow. For instance, a group of cells together produce one hormone, and when its concentration is a certain amount it triggers changes in the way a cell grows, and how much of another hormone other cells release too. Concentrations of some hormones will naturally be highest in the middle of a group of cells and will diffuse away into the water from the edges so that there will be a natural gradient. The different chemicals affect the gradient of other hormones by speeding up production or slowing it down. So there will be regular patterns of hormones throughout the sponge, determining how they grow and the kind of mineral spikes they make."

"Sounds complicated... a bit like how that plant hormone gradient produced at the growing tips of a tree inhibits growth of other parts of the tree, producing the tree's shape, growing at the top and at the ends of branches. And that other hormone that is destroyed by light so it makes cells grow long in darkness and short in light... or is that the same one? And there is another that is affected by gravity too, I think, producing a vertical gradient and making plants grow upward."

"Yes, same principle. But Neil has added a twist. He's altered the genes of his sponge so that one of the hormones that stimulates production of the silica spikes can be enhanced by light. Remember that these spikes can also act as tiny light guides." Myra waited for a little while for that to sink in to her computer programming friend.

"Oh, wow. Does he realise what he has?"

"Unfortunately, no. Odette tried to help him understand, but he is really only interested in developmental biology. He has no desire to consider how this can be used for computing, which is natural, he has eyes only for his own fascinating field."

Janelle was hardly listening. Her mind was racing ahead with the possibilities. "Gosh, if we grow these things on a matrix of microscopic light-emitting diodes then we could train it to respond to patterns, like the neurons in a brain. And if we have photodetectors on the opposite side we can get the output." Janelle almost screamed in her excitement. "Myra, this is big!"

"I agree."

"If we can get light to contol how the light conducting spikes grow and connect to each other then we have an optical memory system that could last beyond human lifetimes... and which anybody can grow for free, at home."

Myra said, "We have more than that, too."

"Yeah, the beginnings of a brain that computes with light. Not a normal computer -- although we might be able to make that too -- but we have the makings of a neural network... like what I guess you emulate in software."

"Exactly." Myra's avatar looked elated.


"Yes, Janelle."

"Did you realise that this might be the result of following this idea through?"

"Not until a few seconds ago. I'm as pleasantly surprised as you are."

"Do you think it can be programmed to be one of you... an AI?"

"I have no idea, but wouldn't it be fun finding out."

Janelle laughed.

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