"The Missing Mass"

by Larry Niven

Midmorning Saturday, the fourth day after the landings, the Draco Tavern was frantic.

You never can tell how the biorhythms of a score of alien species will interact after the landers come down. None of them cycle through exactly twenty-four hours unless they medicate themselves. The first two days I’d been swamped in the mornings. The evenings had been half dead.

Gail, Jehaneh, and Herman were all on duty. Nearing noon, they seemed to have it under control. I could almost relax.

The Draco Tavern is all one room. During the remodeling the bar became a ring in the middle set higher than the main floor, to give me a chance to look around. This many disparate life forms don’t always get along. I’ve learned diplomacy. I’ve got stun gear too.

Four Low Jumbos huddled close around a table, almost hiding it. Low Jumbos like crowds. They only show up when there’s no room for them. Their bodies shook; the roar of their laughter leaked through the privacy shields as a synchronized bass huf huf huf. Their combined bulk nearly hid an entity their own size, the Terminator Beaver working with his computer against the west wall.

Ten Bebebebeque, sixteen-inch-tall golden bugs, perched around the rim of a table conversing with a Chirpsithra and a gray-and-pink jellyfish in a big glass tank of foamy water... big enough to crush my table, it looked like, so it must be sitting on a magnetic float. The jellyfish was new to me. Harsh blue light shone down from the top of the tank, illuminating an intricate internal structure and five dark, wiry tentacles knotted at the center. Evolution beneath a hot, fast-burning sun would explain why they hadn’t adapted to the land... if there was land where they evolved. Water worlds seem to be common.

Jehaneh set a tray on their table. The water creature used skeletal waldo arms to move a pink canape through its little airlock. I watched the canape slide into its translucent interior.

Jehaneh came back to the bar, looking pleasantly bemused. "Carpaccio flavored with sea salt," she said. "Do all the seagoing forms want red meat?"

"Mammal meat is higher energy than they’re used to. They all have to try it, but it makes them hyper. Sometimes they get sick."

"I need four more sparkers," she said, "and four Bull Shots."

There were Chirpsithra at most of the tables. They’re the ones who use the sparkers, and they make and run the interstellar ships. They look like attenuated crustaceans, three meters tall and higher, and red like a boiled lobster.

Four humans in Arab robes settled around a table. Iraqi seem to have rediscovered the pursuit of wisdom. Aliens made overtures, and they broke into pairs. Two joined the Low Jumbos. Two took high chairs to talk to a Chirpsithra.

A man stopped in shock in the double door airlock.

He didn’t look like the usual run of xenobiologist or diplomat. Short, pale of skin, oriental eyes, straight black hair going gray, a comfortable old suit and weird tie, a laptop computer hanging from one hand. He wore the vague look of a scholar with a wandering mind. It took him a moment to recover his aplomb.

Then he made his circuitous way toward the bar, shying wide of aliens, way wide of the Folk, who laughed at him with lolling tongues, like a pack of wolves with their heads on upside down.

I was human. He was really, really glad to see me. He set the computer on the bar and asked, "Can you make me an Irish coffee?" English accent overlaid on something oriental. Having second thoughts, "Leave out the whiskey."

I told him, "I can do coffee any way you want it, or expresso, cappuccino -- "

"Cappuccino would be perfect."

He didn’t try to talk over the shriek of live steam. He opened his laptop and booted it up. In the sudden quiet that followed he said, "I’m Roger Teng-Hui. I’m looking for someone."

I asked, "Human or alien?"

"E-mail correspondent," he said. "I’m looking for Helmuthdip." He turned the Toshiba around. He had World Online up and running.

I read an email message from <Helmuthdip@starlink.net>

If the Chirpsithra have such a power source, they may be willing to share it. A Human diplomat might ask.

I asked him, "Power source?"

"He thinks the Chirpsithra are using the energy of the vacuum."

I let that crypticism go past me. "When did you first contact this ’Helmuthdip’?"

"Wednesday evening."

"What’s he want?"

"He seems to want me to put political pressure on the crew from that starship! At first he didn’t mention politics, interstellar or otherwise. I took him for human."

The chirp liner Scrilbree Zesh had been in place near the Moon last Tuesday morning. The landers were down before Wednesday noon. Give ’Helmuthdip’ a couple of hours to buy a computer in Forelgrad and play with it a little... . I said, "The timing’s tight. You don’t know the species?"

"I thought he was human! He had a website up, a discussion group on the problem of the missing mass. My filter program caught it. The site didn’t look active. It was just him."

I waited.

"I didn’t think I was dealing with a political pressure group. He knew things. He was interested. You know, a dedicated astrophysics site would have been easy before the Chirpsithra came. I’ve been teaching on PBS and the Net for twenty years. Most of my students have disappeared, and I’m the only teacher left."

Herman asked for Arabian coffee for the Iraqi. He took the tiny cups and went off, and I said, "I suppose the problem is that the Chirpsithra know it all."

Teng grimaced. "Do they really?"

"They say so. Their passengers say so. Sometimes they play jokes. I might buy that they know everything they want to," I said, "and what they don’t know, their passengers know, and when they don’t, they bluff. I’m used to it. I never thought about it from a teacher’s viewpoint, but... it must be like everybody’s sitting around waiting for the answers!"

"Flipping to the back of the book. Give me another cappuccino. Grand Marnier on the side. Do they ever make mistakes, or are all of these entities too advanced?"

"Oh, they make mistakes." A qarashteel had come to Earth to make cheap war movies... but I shouldn’t blurt that out to just anyone. "Your alien would still have had to learn how to use the Internet. Maybe a human being showed him. Let me try something," I said. I linked into the Britannica’s universal encyclopedia site, found what I wanted and turned the screen around.

’Helmuth speaks for Boskone.’ Early science fiction. Helmuth was a space pirate, and a ’dip’ is a pickpocket. You’re looking for a spacegoing petty thief. Excuse me." Things had gotten busy around the big table, and I went off to deal with it.

# # #

The Draco Tavern has always been as much a fast food joint as a bar, but our supplies and capabilities have expanded over the years. We charge too much because we have to keep too much stuff around, and we have to be too careful what happens to it. Most of this stuff would poison most of the life forms we get in here, and that does include the booze.

A Chirpsithra knew me, though I didn’t recognize her. You can’t tell Chirps apart; they’re gene-engineered to identical perfection. I gestured at the Low Jumbos and asked her, "Do they like crowds that much? Or should I be getting bigger tables?"

"You would not see the end of that endeavor! These -- " Something breathy -- "are not the largest of our clients!"

Other Chirps chittered laughter. One said, "There are life forms that would not fit in any imaginable vehicle!"

The other, "But were they sapient? How could we ever know?"

Chirpsithra obscurities. I moved on. We were frantic for the next hour.

Then the Iraqi all rose and went out -- prayer time, I guess -- and suddenly most of the bar was getting up and walking, rolling, lurching, slithering through the airlock into a horizontal glare of Siberian tundra. The Low Jumbos followed the rest.

The jellyfish in his aquarium was still there. I wondered if he’d been abandoned. Five Chirpsithra who had watched their alien companions all go away, now gathered around the big table with the aquarium in the center. Herman glanced my way for permission. I thumbs-upped him. He pulled up a high chair and joined them. Something hairy came out of the restroom, looked around at the empty bar, then joined Herman and the chirps and jellyfish.

Jehaneh looked tired. I told her to go sack out. Gail went too. Roger Teng-Hui was still at the bar working his Toshiba. The Terminator Beaver was deeply involved with his Macintosh.

I stopped at the Beaver’s table.

What showed of him was largely prosthetic. Under all the goo and wire and silver plating and small glowing icons the Terminator Beaver might have been a solitary Low Jumbo. He was half covered in tiny black platelets, half pink hide bared for prosthetics. Circuitry, lenses, armor covered his body. The material shone like glass and metal and jelly, but it all flexed. There was a narrow indicator strip above his small, neat carnivore’s mouth, where he could read it with goggles like two silver eggs. The widgetry had a functional beauty implying, I thought, centuries of design. It hid most of his face.

Wires ran from a neck ring into the ports of the Macintosh. The screen was dancing, flickering, and his fingers never went near it.

He’d told us his name: a near-supersonic birdsong. He had been in the Draco Tavern since the landings, eating and drinking alone. He had bought the Macintosh laptop computer in Forelgrad, the merchant town that has grown up around the spaceport. Gail had shown him the basics during a dull evening. He’d become skilled very rapidly.

We’d speculated. The Draco Tavern’s elaborate restroom isn’t gender-specific, so we still didn’t know that. Was he, she, it a cyborg by choice, a medical patient, geriatric case, augmented athlete? Was he an injured Low Jumbo avoiding eyes that might find him ugly?

He’d plugged his Mac into the wall, not into one of the universal sockets the Chirpsithra gave us, but into a telephone jack. I looked back toward the bar. Teng-Hui was around the other side, not visible.

The Beaver might well be the mysterious <Helmuthdip@starlink.net>. Did I want Teng-Hui to know that? Did I want to tell the Beaver about Teng-Hui?

I try not to get myself or the Tavern involved in these dominance games. Sometimes there’s no helping it. And sometimes I can supplement our income by learning something valuable. I once went broke building a supercomputer, but that’s also how I patented the magnetic float.

The game the Beaver was playing wasn’t an action game, so I felt free to interrupt. "Terminator Beaver," I said, and let my translator whistle his name, "How are you doing?"

Let him take it either way: progress on the game, or was he thirsty?

He whistle-sang. His translator said, "Dead. Notice joke. I begin the game dead."

"Your character can still get hurt." He was playing Grim Fandango upgraded for 3D. I watched him trying to deal with the coroner and his flower beds. "Do you enjoy hints?"


"I need a hint to a puzzle. How good are you with that thing?"

"A fascinating toy."

"Have you had dealings with this entity?" I showed him the net address: <Helmuthdip@starlink.net>.

He asked, "Do you have access to this entity?" He typed it on the screen: <chinaRoger@wol.com>

"It may be. Describe what you want of him."

"A matter of negotiations. Rick Schumann, why should I tell you more?"

" ’ChinaRoger’ hasn’t dealt with aliens."

"You have had much experience. I have funds if you will act as a mediator," said the Terminator Beaver.

"I’ve done that," I acknowledged. "How difficult is my task to be? Try to describe what you want of ’ChinaRoger’."

"I seek knowledge that would point to energy for industrial purposes."

Guessing, I asked, "Something to do with the missing mass?"

"I wondered if you merely pretended to knowledge. Would you accept one-over-twelve-cubed of net profits from this process over the next thousand years?"

I negotiated for half that, plus a modest thousand credits to be transferred at once. A bird in the hand, etc.The recording would serve as a contract if I brought these two together. I hadn’t decided on that. Either way, I expected no profit from this.

# # #

Herman was getting recharged sparkers for his table. The Wheesthroo, the hairy guy, wanted an orange sherbet shake in odd proportions. I made that and Herman took it away.

Teng had waited patiently. I asked him, "What do you want with this Helmuthdip?"

"I want to know what he wants with me."

"What’s he say he wants?"

"That’s complicated."

"I’m not busy."

"I thought he was just another astrophysicist. But, look, I’m Roger Teng-Hui. Any decent astrophysicist knows who I am, and I’d know who he was. I don’t mind ’Helmuthdip’ hiding his name. But he knows of research I’ve never heard of, and there are terms he didn’t know. That was funny. He wanted to talk about the expanding universe, but he didn’t know ’Hubble constant’. He knew ’missing mass’, but he didn’t know ’Casimir effect.’"

"I don’t either."

"Ah. Look, this is fascinating stuff -- " He caught himself. "Even now. Rick, the current most interesting question in astrophysics is, what is the nature of the expansion of the universe? Will the universe expand to infinity, or will it collapse back to a point? Most astrophysicists would like to find just enough matter to make space flat.

"Understand this picture? If the universe is too massive, it’ll expand for awhile and then fall back into a reverse Big Bang. If there’s not enough mass, it’ll be expanding toward infinite volume. Right between, it expands to a finite limit. That’s flat space, right between infinite expansion and an eventual collapse, and it fits a cluster of theories built around an inflationary universe. How fast we’re expanding is the Hubble constant."

I did in fact understand him, but he didn’t wait to find that out, he just raced on. "Now, the right amount of matter to do that depends on how fast the galaxies are going away from each other... the Hubble constant, right? The faster they’re flying apart, the more energetic the Big Bang explosion must have been, and the more mass it will take to pull everything to a stop.

"The point is, none of the astronomers can find enough mass to do the job. Maybe we would have. Telescopes were getting better all the time, but then the Chirpsithra showed up -- "

"Is this what was going on at ’Helmuthdip’s’ website?"

"Yes. I thought he was an amateur at first. Brilliant amateur. I was intrigued.

"The latest, most accurate measurement of the Hubble constant depends on Type 1A supernova explosions. Do you know how that works?" I shook my head. "Say you’ve got a bloated gas giant star losing mass to a white dwarf companion. The hot hydrogen gas rains down through an amazing gravity field, so it’s heated to tens of millions of degrees. When it gets dense enough, you get a fusion bomb, boom.

"These Type 1A’s all resemble each other, and they can be recognized across huge distances. The universe is full of them. A Type 1A supernova tells you how far away it is by how bright it is, and how fast it’s moving by its red shift.

"Using those as meters to measure the universe, we get a rate of expansion that suggests around thirty percent of the mass that’s needed to close the universe, or ten percent, or seventy percent, depending on who needs a grant."

"So you look for more mass."

"Right! We look in places obscure and weird. We postulate mass we can’t see, dark matter, in all sizes from neutrinos to intergalactic dust, to near infinities of brown dwarf stars, to hypothetical massive particles left over from the Big Bang itself. I wasn’t a front runner in all this, but I kept track. And I got old, and we had too many solutions and none of them made a lot of sense. Aliens came down in Siberia, hordes of them, and they know. So what was the point?

"Then ’Helmuthdip’ popped up on my screen. And for awhile he was making sense, and then he got into the Casimir effect."

"What brought you here?"

"And then he started insisting that I use my influence on the pilots of an interstellar liner! That would have brought me here anyway, but what influence? If he comes from a place where astrophysicists have more power than fucking politicians, it’s for damn sure he’s from interstellar space! But I have to tell you about the Casimir effect."

"Do you really?"

"Actually," he said, "no. Let’s leave it that there’s energy in the vacuum. Fantastic levels. Space isn’t really empty, it’s a froth of virtual particles appearing and annihilating each other faster than any hypothetical instrument can detect them, and that’s where the energy is. It’s been demonstrated mathematically that if the vacuum in free space was empty of energy, you’d have minus energy near a black hole.

"The Casimir effect is an experiment that measures vacuum energy. You machine two plates very flat, and you move them very close together. They pull at each other -- "




"It’s done with virtual particles. Virtual particles flash into existence and annihilate each other everywhere in space. But you put these plates so close together that the wavelength between the two plates is too small. There’s no room for virtual particles to pop up between them. The pressure on the outsides pushes the plates together, and that’s the Casimir effect."


"Tiny. ’Helmuthdip’ has been trying to tell me -- Is that entity waving at you? The half-mechanical, ah, person?"

The Terminator Beaver was on his feet and coming around the bar. I said, "Terminator Beaver, meet Roger Teng-Hui, also known as ’chinaRoger’. Teng, meet ’helmuthdip’, aka Terminator Beaver. I believe you have much to discuss."

# # #

They sat at the bar with their computers in front of them, sometimes activating displays to supplement the Chirpsithra translators. They both kept slipping into jargon, then remembered that they were talking to the bartender too. Sometimes it takes a third party to get two people talking the same language.

"The Chirpsithra won’t discuss what powers their star-to-star liners," the Terminator Beaver said. "Our landers are various and we build them ourselves, but the liners have apparent infinite power and not enough fuel storage."

"Antimatter?" Teng asked.

"Antimatter they keep for attitude jets, with dross from refined sewage as reaction mass. Our landers use antimatter. Spies have identified a system aboard Scrilbree Zesh for making antimatter! Where do they get the energy? Many species wish to solve the puzzle. Sometimes we cooperate. We know that the liner’s mass varies during a voyage, losing and gaining again."

"The energy of the vacuum is thinly spread," Teng said.

"By some measurements," the Beaver agreed. "Some theories render it huge. The Casimir effect may measure only the least of what is available."

I saw fit to cut in. "Near-infinite energy in the vacuum," I said, "And near-infinite energy in these huge Chirpsithra ships. That isn’t all of your argument, is it? Because they don’t have to be related."

They both tried to interrupt. The Beaver’s translator cried, "No, no, no! What of the missing mass?"

"He was doing that before," Teng said. "It’s an interesting... notion."

"We must suppose that early Chirpsithra -- " The Beaver saw us about to object. "No? Then think of engineers who find a way to attain the energy of the vacuum. When work is done, something always disappears, does it not? Not energy nor potential nor mass, unless one into the other, but something is gone."

"Entropy," Teng said. "Disorder increases. Energy becomes less available."

"Yes, but what is gone when energy is taken from the vacuum?" The Beaver’s silver goggles flickered as he studied our faces. "You cannot pull energy from the same volume over and over!" he snapped. "Vacuum must disappear!"

I said, "Okay -- "

"They learn the ultimate secret, these Engineers. They may be the first of many. Their numbers and ambitions expand. Peculiar and active galaxies may show their work. There is no missing mass," the Beaver said. "The universe is expanding too fast, the Bang was too energetic, but expansion slows because space is disappearing. In the limit, space will be flat."

I asked, "Teng? Is this even sane?"

The man said, "Oh... sane. Look, there’s no way you can take the same energy out of the same block of emptiness forever. Energy has to become less available. Sure something has to go, and it’s probably volume. Space shrinks where the Engineers have passed. Why the Chirpsithra?"

"Look about you. They have such a power source! How many suspects can you identify?" the Beaver demanded, rather unfairly, since the bar had been nearly emptied.

Teng said, "Well, that’s my point. This universe has had around ten to the tenth years to produce a species capable of using the energy of the vacuum. We expect the universe to last... how long before interesting things stop happening? Ten to the fortieth years? Ten to the ten to the eighty? We are in the earliest moment of the universe. Most of time is in front of us. The Engineers might not even have a planet to evolve on yet! They may evolve after all the protons have disappeared."

I said to the Beaver, "You have asked the Chirpsithra, haven’t you?"

"To us the Chirpsithra said nothing. To another race they once said that the secret of their drive was to be taken as a puzzle. ’Just another cursed intelligence test.’"

Teng burst out, "Your damn hypothesis isn’t even falsifiable!"

I asked, "What?"

"When you’ve got a decent theory, you try to falsify it, Rick. You don’t want someone else making you look like a fool, so you try to disprove it yourself first. If a statement can’t be disproved, falsified if it’s false, it’s useless. Beaver, if the Engineers won’t start chewing up galaxies for a trillion trillion years, what evidence would you expect to find now?"

"Any species may ask."

"Not us," Teng said, suddenly bitter. "There weren’t even human footprints on Mars when the Chirpsithra came. If ever there are, they’ll be around a Chirpsithra landing site. Passengers. Why would they give us an interstellar drive? We can’t even build landers, and they use antimatter just for reaction jets!"

I made two cappuccinos while I thought. All talk stopped in the scream of steam.

It seems I’m doomed to spend my life with entities brighter and more knowledgeable than myself. They gather to talk, all these different shapes and minds, and I am priveleged to listen. I love it. But sometimes they talk and talk, and never act.

A mathematician once told me that all of math is a mind game. The strangest thing is that any of mathematics can be fitted into the way any part of the universe behaves. The huge vacuum energies that fall out of mathematical formulations needn’t be taken seriously. I knew that without ever seeing the equations, let alone being able to read them.

Then again... "Come with me," I said. "Let me do the talking. Teng, you may not know it, but any ongoing conversation should not be interrupted. It’s a custom."

"Right. What have you got in mind?" But I was in motion, and what I had in mind was very little.

# # #

The big table was down to Herman, three Chirpsithras, the silent Wheesthroo, and the big jellyfish in his aquarium jar. I placed the cappuccinos and pulled up high chairs for the rest of us. One of the Chirps was chittering. My translator said, "Not all of the life forms known to us enter the Draco Tavern. Poseidon masses as much as Scrilbree Zesh itself." Scrilbree Zesh was the big ship still orbiting the Moon.

The jellyfish spoke like a snore. Its translator asked, "But this entity could visit Poseidon?"

"One of our ships might cross to Poseidon’s world. We would prefer to visit Poseidon before he dies. Wait but a moment." The Chirp’s monitor strip twinkled.

Herman took the opportunity to half-whisper, "We’ve been talking about water worlds. That’s Scylla. Nothing to trade, but supposed to be a poet. Poseidon lives on a water world not far from here. He’s huge."

The Chirp said, "No such voyage is now planned. Learning to talk again to another of his species would be tedious, but we estimate Poseidon’s lifespan in the thousands of years."

"But mine is not," Scylla the jellyfish said.

"We are sorry. Greeting, Rick."

"Greeting, elder. Greet Roger Teng-Hui and the Terminator Beaver."

"Greet you both. Greet Scylla, whose kind only recently made fire. A great accomplishment it was."

We spoke; the translators spoke; talk grew raucous, then stalled. Into a moment’s pause I asked, "What’s the largest life form the Chirpsithra know of?"

"Extinct now," the Chirp said. "They were larger than galaxies. They formed the galaxies. Your telescopes will one day be powerful enough to watch them. Would you witness this now?"

Teng wanted to speak. The Beaver wanted to speak. But they both looked at me first, and Scylla’s snore rang out. "Please show us this wonder."

"Our monitors... but you have a local computer, I see." The creature’s long red armored hand reached out for the Beaver’s Macintosh computer and opened it facing the jellyfish. "Do not disconnect." The chirp produced a little box of its own and plugged it into a piece of the Beaver’s equipment. Her fingers played over a surface.

The Beaver was still attached; he twitched. The Mac’s screen raced, went black, then blue-white. "Fast-forward," the Chirp said.

We watched. A wash of violet light dimmed to blue, to green, to yellow, then broke into an expanding chaos of filaments and dimmed further.

The Chirp’s translator spoke. "Roger Teng-Hui, how do galaxies form?"

Teng said, "It’s a puzzle. Current attempts to model the early universe usually give us a universe that is too uniform to form galaxies. Inflationary theories make galaxies more likely. It’s one of the attractive things about inflation."

She said, "You have not yet seen the universe forming. It was too uniform. Without galaxies there would be few stars, yet galaxies would never form. But like all here -- even Scylla, whose sea-locked kind breed transparent jellyfish to make ever more powerful telescopes -- we became able to watch."

Out of the chaos came whirlpools of light.

"It may be you cannot see the mechanism. Teng, your people have wondered about the missing mass." Teng recoiled; she chittered laughter. "What is unfalsifiable might still be proven true."

"You’ve been eavesdropping," I said.

"Our translators note key phrases, as ’missing mass’ in conjunction with ’energy of empty space’. If engineers must use the power in the vacuum, and those engineers are yet to evolve, then they will be undiscoverable. But these life forms we call the Firstborn evolved very early. They metabolized the energy of the vacuum. Wherever there was a bloom of Firstborn, an orgy of uncontrolled breeding, there too were sudden concentrations of mass. Disappearance of volume leaves mass behind, yes? There sudden stars flowered.

"We would study the Firstborn further, but we cannot find them. We fear them extinct. The rage of light and heat may kill them when galaxies form, or else matter around them might grow denser until a black hole swallows all, and remain behind to anchor a galaxy.

"Yet we hope that they still survive between galactic clusters. See this great emptiness -- " She showed us on the Mac, a vast hole in the universe where there were no galactic clusters. "We have never traveled that far. If we could study the Firstborn, we might learn their secret."

The Beaver demanded, "But what drives your ships?"

"Our ships use a lesser effect. The Firstborn hold the key to vast wealth. If we have not learned it, we, in our billions of years... well. Some younger race might. Teng, Beaver, Rick, it is not in our interest that you should give up striving."

# # #

Scylla’s magnetic floatplate floated out from under the table, and she drifted out onto the tundra. The rest followed. I watched them go, thinking that we must be a common thing to the Chirpsithra. A civilization is only beginning to learn the structure of the universe, when interstellar liners appear and alien intelligences blurt out all the undiscovered secrets.

Primitive peoples die when powerful intruders mock their lifestyles. Whole worlds might be saved, if Chirp diplomats can be trained to imply that vast secrets remain untapped, awaiting the touch of young and ambitious minds.

"Paid you too much," the Beaver told me. "Did you see animals the size of a galaxy? I did not. I saw blobs and colors." He ambled out.

Teng caught up with him. I heard him say, "Let’s think about expanding that ’Helmuthdip’ website. Get some of my colleagues involved. Maybe some passengers too." Teng was bouncing, his spirits restored. In a young universe there were still wonders to achieve, secrets for a young species to learn.