Four greats is a long time to wait before you can finish your thesis," she said.

"We didn't have to wait at all," said Time-Circle. "Somewhere there was a minor calibration error between the forward-time channels and the back-time channels.Before we sent out the test signals, we received a response back from the future saying that all the signals had been received and giving the number of bits that had made it through each channel. They all agreed with the theoretical prediction of 864 bit-greats."

"But suppose you had then decidednot to send the test messages into the future?" she asked.

"One of the students suggested that," he replied. "But I had already trod their edges on that subject early in the project. Until we have a theory for these machines so we can understand the implications of creating a paradox, we can't afford to take a chance.My guess is that every major paradox causes a bifurcation of the universe. But it would take a good theory to suggest an experiment that wouldprove that bifurcation had taken place."

"And you have a good theory?" she asked.

"Until a few turns ago, I thought I did," he said dejectedly. "Now, I'm not so certain."

"What happened?"

"After the success with the three multi-great transmissions, I had no trouble getting the grant committee to authorize the construction of a 24-channel machine with a greatly increased channel capacity in each channel. Getting the money approved took a while, and while the preliminary design work was underway the time came for the first of the transmissions to be received, the one sent over two greats of turns. The two ex-students as well as members of the grant committee were there as the message came out of the machine from two greats in the past, and they watched as I measured the bit count and sent the confirmation back to myself in the past. I should have quit then."

"What happened?"

"Since I now had two channels free in each direction, I decided to show the committee how the Time-Comm machine worked by sending a messagesix greats into the future. As I prepared the message for the forward-time channel, I was a little surprised that the back-time channel had not already indicated the message had been received. Thinking that the differential calibration had drifted off so that the back-time channels were now shorter than the forward-time channels, I sent the message off six greats into the future and waited for a reply."

"And?"

"It didn't come," he said. "I didn't find out what had happened until a great of turns later, long after the grant committee had decided to hold up on the construction of the new machine."

They had finished eating, and the faculty dining compound was nearly empty.

"You have to get back to your work," he said. "I can't do anything until the next channel clears a few dozen turns from now, so you spread the fields and I'll snuggle along behind and tell you the rest of the sad story."

She headed across the grounds of the Inst.i.tute and he switched to a soft electronic whisper that tickled through her hide.

"I was really dejected until the time came for the reception of the three-great-long message. That came through on schedule, and I sent the reply through the back-time channel. Almost as soon as the reply was on its way through the channel into the past, the channel was full again with a message from the future, eight greats away. At eight greats time distance, you can only send 108 bits of information, so the message was brief. Both the six greatand the eight great messages had been received, but the response to the six-great message had been blocked by some spontaneous emission in the back-time channel."

"Spontaneous emission?"

"That bewildered me at first. My time communication theory, although based on the quantization of s.p.a.ce and time, didn't predict any spontaneous emission of signal energy in the channels," he said. "I brought in a bright theoretical student, and we soon found a third-order effect that could produce spontaneous emission of a bit pair that travels simultaneously backward and forward in time for a short period, then emerges in the receiver. Even though the 'message' is only one bit, that is enough to keep the channel from being used by any other message. It is only supposed to happen once every dozen generations or so, and it had to happen just as I needed that channel to impress the committee."

"Did your new results get the committee to resume the work on the 24-channel machine?" she asked.

They were just as suspicious of the coincidence as I was," he said. "They decided to wait until we saw the noise in the channel and could learn more about it than could be sent with 108 bits. Sure enough, about 72 turns later, out came a single bit and the channel indicator registered 'Channel Occupied' for almost two greats when suddenly the back-channel was empty and a forward-channel was 'Occupied.'

Neither transmitter had activated. I a.n.a.lyzed and re-a.n.a.lyzed everything and was about to approach the committee for restarting the construction of the new machine when the final blow fell."

Neutron-Drip stopped moving, and her edges flowed back about his in a semicircular embrace.

"Last turn I responded to an alarm and found that another back-time channel has noise in it. What is worse, it was not a single bit, but three bits with a nonsense meaning. The chance of spontaneous emission of three bits is infinitesimal. The machine has a noise source. And until we understand it, we shouldn't spend money on a larger machine. But with only four channels, it will take forever to find out what the problem is."

"But once you find out, you can send a message back to yourself with the answer ..." she started.

"There you go, creating paradoxes again," he said. "If it were possible, 1 would have already done it, and 1 wouldn't be here whispering my troubles into your trailing side." He moved around her and pushed off across the compound.

"Enough of my problems," he said. "How about showing me how you are going to set up that net around the East Pole to trap crustquakes?"

06:57:52 GMT TUESDAY 21 JUNE 2050.

Qui-Qui was surprised when she received a letter from the rejuvenation selection committee. She sent her acceptance message at once, then called her manager, Grey-Stone.

The picture over the video link was that of a small middle-aged male painted in the bright diagonal stripes that went out of fashion 20 greats ago. The already rapidly moving eye-wave pattern became even more agitated as he recognized his famous client.

"What problem have you got now?" said Grey-Stone. "You never call me unless you've got a problem."

"No problem at all," said Qui-Qui. "It's good news. I have been selected by the rejuvenation committee for treatment. Of course, the treatment takes a half-great."

"Ahalf-great!" came the loud reply over the video link. "You don't have a half-great free on your schedule until 2899!"

"I do now," she replied. "I go west for the final interview and tests two turns from now. Unless they find something that disqualifies me, I start treatment immediately after that."

"But your contracts ..." Grey-Stone said.

"Renegotiate them," she replied. "Just remind them they will be getting the experience of an old, flabby Qui-Qui in the body of a young, firm Qui-Qui."

She watched the traveling wave motion in Grey-Stone's eye-stubs slow to almost a complete halt as he pictured the image she had created.

"At twice the original fee!" he finally said.

"That's why I have you for my manager," she replied with a rippling overtone in her tread. "There is nothing too audacious for Grey-Stone."

She paused, and her eye-stubs stood still while she rippled her bountiful eye-flaps in her famous gesture of shocked, innocent bewilderment.

"Of course ... it could be ... ," she said, the ripples of her eye-flaps coming to a stop. "That ... the treatment leaves me flat." She flicked off the video with a chirp of amus.e.m.e.nt as Grey-Stone's eyes stood straight up in shock.

Qui-Qui programmed her housekeepers to keep her three compounds in shape while she was gone and took the Jump Loop to the West Pole Rejuvenation Center. She had been a.s.signed there to be close to her clan home of White Rock City. At the Rejuvenation Center she had no problem pa.s.sing all the physical examinations. The last step was a final interview with the senior physician in charge of the Center, Sabin-Salk. During the examinations, Qui-Qui had had plenty of time to think. Now she had some questions.

"What I don't understand," she said, "was why I was selected instead of some scientist or writer or musician or politician?"

"According to our evaluation, you happen to be one of the best cheela ever laid on Egg," Sabin-Salk said matter-of-factly. "You are an expert in communication with other cheela. With a different background or training you too could have been a writer or a musician or a politician, perhaps even a scientist, in fact, if it weren't that you are too honest to deceive people, with your intelligence, good looks, and charisma, you could probably even convince people you were a G.o.d and start a new religious cult."

"But all I am is an entertainer," she protested.

"I don't think even you believe that," he said. "To the average holovid viewer you are nothing but twelve big eye-flaps. But those who have talked with you know that behind those eye-flaps is one of the tightest brain-knots on Egg. You have a lot of friends in large compounds. Your choice was no accident.

"Now, let me take you around the treatment facility and show you what you must undergo. The procedure will not be easy." They entered the first compound where there were a couple of robotic attendants and a lot of exercise equipment.

"First we must exercise you and feed you until you have built up a good supply of flesh in your body.

The dissolver enzymes will use that as the building material to produce support structures in the intermediate plant body. Those support structures must be of high quality or they will break in the strong gravity of Egg."

Qui-Qui noticed someone exercising under the guidance of a robot in the far corner of the room. It was a large male, almost as large as she was. The robot spoke something to the male, who muttered curses as he increased the tempo of his exercise.

"Who is that?" asked Qui-Qui.

"It is Engineer Cliff-Web. He owns Web Construction Company."

Qui-Qui's eye-wave pattern slowed in puzzlement. She obviously didn't know who Cliff-Web was.

"He was the one who built the s.p.a.ce Fountain and the Jumbo Bagel s.p.a.ce motor to rescue the Slow Ones," said Sabin-Salk.

All of Qui-Qui's eyes turned to look in awe at the engineer.

"I was selected with someone that important?" she said.

"Actually, he was in the first selection list," said Sabin-Salk. "But he is quite a bit older than you and, having been involved with scrollwork much of the time, he was in poor physical condition. He was in the exercise phase for almost 40 turns before he had sufficient muscle tone. Two more turns of starving, and he will be ready for treatment."

"Starving!" Qui-Qui gasped. "I thought you said we were fed."

"You are fed during the build-up phase," Sabin-Salk explained. "But we must have your well-muscled body starving and near exhaustion before we inject the animal-plant conversion enzymes. They then activate the dormant genes in you that were left after our evolution from the dragon plants long ago." He paused and observed her carefully as he continued. "I warned you that it would not be pleasant. If you would rather not take the treatment...."

"No. I want to go ahead with it," said Qui-Qui. Her eye-stubs wavered to a halt as she asked her next question. "Will I still be conscious during the burning part?"

Dr. Sabin-Salk looked bewildered, so she continued.

"I am of the clan of the Ancient One Swift-Killer, the first cheela in recorded history to undergo rejuvenation. In the hatchling pen I was told how she struggled to climb the East Pole mountains to send the first message to the humans. After sending the message, her exhausted body was severely burned by the heat from an infalling meteorite. The burning caused her body to revert spontaneously to the dragon plant form, where the damage was mended. Later the dragon plant reverted back, and Swift-Killer found she had a new, young body."

"Swift-Killer was extremely lucky," Sabin-Salk stated. "Most cheela who have tried the burning approach to rejuvenation died. The only function of the burning was to shock the body and get it to produce the animal-to-plant conversion enzymes. We do not burn you. Instead we manufacture the enzymes artificially and inject them into you. They dissolve everything in the body except the nerve tissue and the outer layer of skin. That liquid is then used to make the plant."

They left the still exercising Cliff-Web and moved on to the next compound. A large array of small machines stood in one corner of the compound, each with two tubes that connected to two larger collecting lines that led to two large tanks. A single robot was tending the machines.

"Those machines produce both the animal-to-plant and the plant-to-animal enzymes," said Sabin-Salk.

"It takes all those machines about 18 turns before we have enough for one rejuvenation."

"Only one patient every 18 turns?" exclaimed Qui-Qui. "Surely you could handle more than that!"

"We will," Sabin-Salk told her. "As more of the enzyme producing machines are produced, we will increase the treatment rate to at least one per turn. It will take some time though, since the other centers are also awaiting machines."

"They don't look very large," said Qui-Qui. "You would think there would be plenty of money available for the production of rejuvenation machines. I guess they are complicated inside."

"The problem isn't money or the difficulty of making the machines," said Sabin-Salk. "The process for producing the enzyme requires the use of a rare catalyst. It is a neutron-rich isotope found only in trace amounts in the lava shield from the Exodus volcano. Since the volcano is still quite active, mining the lava is extremely hazardous. It will take a dozen greats before we have enough of the catalyst to reach full capacity. Let us go on to the 'garden.' "

They moved to the next compound. In the center of the compound were two very large dragon plants.

They were of the single-root, inverted-canopy type similar to a parasol plant, but much larger. One of them was still growing and had a small crowd of robots and two live cheela attending it. The cheela had large medical badges in their hides with extra stars and colored spots to indicate their advanced degrees.

"That is what you will look like in 30 to 36 turns if you do your exercises properly." Sabin-Salk motioned to the plants with a flick of his eye-stubs.

"Who were they?" Qui-Qui asked in a subdued electronic whisper.

"Arethey," Sabin-Salk corrected. "You would know them if I told you, but our policy is not to identify the plant form to strangers. Cheela do not mind being pointed out if they are wearing their body paint and badges, but you put all that aside when you are a plant. The larger plant is almost ready for re-const.i.tution. We will let it mature for two more turns, then inject the plant-to-animal conversion enzyme. The reverse process only takes a few turns. The plant support structures are turned into fluid and used to rebuild the body. At the very last stage, the old outer skin peels off and the newly formed eyes come out from under their eye-flaps."

"Is everything the way it was before, except younger?" asked Qui-Qui.

"Everything except the brain-knot and the rest of the nerve tissue, since they are not touched by the animal-to-plant en- zymes. Except for a blank period during the rejuvenation process, the memory and brain function of the new body is identical to that of the old." He paused and deliberately looked off in the distance as he continued. "Since you are a professional holovid performer, I am sure you are interested in what your new body will look like. I can a.s.sure you and all your loyal holovid viewers that the rebuilt body will use the same genetic tri-string that made the original Qui-Qui, and the new Qui-Qui will take up just as much volume on the holovid as the old one."

A directional call signal vibrated through the crust that tickled the outer edge of Qui-Qui's tread as it focused in on the position of Sabin-Salk.

"An Elder from your clan has arrived to approve the final scrollwork," Sabin-Salk said. "If you will follow along behind, I will spread the way to my office."

06:58:06 GMT TUESDAY 21 JUNE2050.

Zero-Gauss had left the faculty dining compound after a nourishing turnfeast and headed for her underground magnetic-field-free laboratory. She pa.s.sed by some students who stopped their conversation to allow their treads to listen to her. She seemed to be simultaneously talking to herself and emitting squeaks.

"I have a delicious piece of baked Flow Slow egg for you. I wiped off most of the sauce so it shouldn't be too hot," she said as she formed a manipulator, reached into a holding pouch to extract the tasty morsel, then put the manipulator into another pouch. As the orifice of the pouch opened, a fuzzy little Slink hatchling tried to climb out, but was distracted by the sight of the food. It grabbed it eagerly and tried to stuff it all into its too-small eating pouch.

"A little too big for you, Poofsie?" she asked. Her manipulator sliced the bit of egg into smaller pieces, which were greedily devoured by the hungry hatchling. She closed the orifice just enough to keep the animal inside while allowing a small hole so he could keep a few eyes waving about outside to see where they were going.

She entered a small compound that was the,top of her unique research facility, which contained subcompounds for her office and those of her graduate students. A second com- pound a short distance away contained the machinery that operated the underground machinery and provided the cooling for the simulated sky hanging beneath the strong superconducting roof of the laboratory. The second compound had a very unusual structure in one corner-arectangular box made of thick metal with a door in one end and a covering over the top.

She went to her office and glanced through her computer net mail. There was nothing important, so she paid a visit to a compound containing two of her graduate students.

"How are the plants doing, Careful-Mover?" she asked one student.

"We did have one fountain plant die," Careful-Mover replied. "It shot seeds all over the room as it did so. But it had lasted 46 turns, which is close to a record."

"Did you get all the seeds picked up?" Zero-Gauss asked.

"Yes. And in the process, Fuzzy-Crust and I found another 'hot spot' in one corner," said Careful-Mover.

"Is it bad?" Zero-Gauss asked. "I'd hate to have to go through the process of pumping out the whole lab again so soon."

"It was 100 gauss right on top of the hot spot," Careful-Mover answered. "But it's quite small, and a few millimeters away it fades into the background variations of a few gauss. There were a few plants near the corner so we just moved the containers to another part of the room."

Zero-Gauss turned to Fuzzy-Crust.

"I have a replacement for Peter," she said, pulling the tiny ball of fuzz and eyes from her pouch.

"Poofsie, meet Fuzzy-Crust. He will be taking good care of you from now on," said the professor, forming a little nest on the floor with the edge of her tread and dropping the animal into it. The Slink tried to climb over the edge, but Zero-Gauss kept it in place by rippling her skin underneath the tiny tread. The Slink stopped and looked up at Fuzzy-Crust with all twelve of its dark red eyes. The student brought an eye down to look at it.

"So now it will be Flopsie, Mopsie, Cottonball, and Poofsie," said Fuzzy-Crust. "You found an excellent replacement. It looks just like Peter."

'These genetically pure strains of laboratory Slinks all look the same," said Zero-Gauss. "I just chose the one that looked the smartest."

"You should have chosen the dumbest one," said Careful- Mover. "Peter was smart and look what happened to him. He figured out how to open his cage and died of overeating. Set my zero-gauss horticulture thesis back half a great."