
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 Id 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 dont always get along. Ive learned diplomacy. Ive got stun gear too.
Four Low Jumbos huddled close around a table, almost hiding it. Low Jumbos like crowds. They only show up when theres 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 waterbig 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 hadnt adapted to the landif 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 theyre 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. Theyre 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 didnt 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 didnt 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, Im Roger Teng-Hui. Im looking for someone.
I asked, Human or alien?
E-mail correspondent, he said. Im 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. 
Whats he want?
He seems to want me to put political pressure on the crew from that starship! At first he didnt 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 timings tight. You dont 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 didnt look active. It was just him.
I waited.
I didnt 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. Ive been teaching on PBS and the Net for twenty years. Most of my students have disappeared, and Im 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 dont know, their passengers know, and when they dont, they bluff. Im used to it. I never thought about it from a teachers viewpoint, butit must be like everybodys 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 moviesbut I shouldnt 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 Britannicas 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. Youre 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 didnt recognize her. You cant tell Chirps apart; theyre 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 breathyare 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 outprayer time, I guessand 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 hed 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 Beavers 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 carnivores 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.
Hed 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. Hed become skilled very rapidly. 
Wed speculated. The Draco Taverns elaborate restroom isnt gender-specific, so we still didnt 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?
Hed 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 theres no helping it. And sometimes I can supplement our income by learning something valuable. I once went broke building a supercomputer, but thats also how I patented the magnetic float. 
The game the Beaver was playing wasnt 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?
No.
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 hasnt dealt with aliens.
You have had much experience. I have funds if you will act as a mediator, said the Terminator Beaver.
Ive 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 hadnt 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.
Whats he say he wants? 
Thats complicated. 
Im not busy. 
I thought he was just another astrophysicist. But, look, Im Roger Teng-Hui. Any decent astrophysicist knows who I am, and Id know who he was. I dont mind Helmuthdip hiding his name. But he knows of research Ive never heard of, and there are terms he didnt know. That was funny. He wanted to talk about the expanding universe, but he didnt know Hubble constant. He knew missing mass, but he didnt know Casimir effect.
I dont 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, itll expand for awhile and then fall back into a reverse Big Bang. If theres not enough mass, itll be expanding toward infinite volume. Right between, it expands to a finite limit. Thats flat space, right between infinite expansion and an eventual collapse, and it fits a cluster of theories built around an inflationary universe. How fast were expanding is the Hubble constant. 
I did in fact understand him, but he didnt 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 theyre 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 Helmuthdips 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 youve 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 its heated to tens of millions of degrees. When it gets dense enough, you get a fusion bomb, boom.
These Type 1As 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 its 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 thats 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 cant 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 wasnt 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, its for damn sure hes from interstellar space! But I have to tell you about the Casimir effect. 
Do you really?
Actually, he said, no. Lets leave it that theres energy in the vacuum. Fantastic levels. Space isnt really empty, its a froth of virtual particles appearing and annihilating each other faster than any hypothetical instrument can detect them, and thats where the energy is. Its been demonstrated mathematically that if the vacuum in free space was empty of energy, youd 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
Gravity?
No.
Oh.
Its 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. Theres no room for virtual particles to pop up between them. The pressure on the outsides pushes the plates together, and thats the Casimir effect.
Strong?
Tiny. Helmuthdip has been trying to tell meIs 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 wont 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 liners 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 isnt all of your argument, is it? Because they dont have to be related. 
They both tried to interrupt. The Beavers translator cried, No, no, no! What of the missing mass?
He was doing that before, Teng said. Its an interestingnotion.
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 Beavers 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, Ohsane. Look, theres 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 its 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, thats 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 lasthow 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, havent 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 isnt even falsifiable!
I asked, What?
When youve got a decent theory, you try to falsify it, Rick. You dont want someone else making you look like a fool, so you try to disprove it yourself first. If a statement cant be disproved, falsified if its false, its useless. Beaver, if the Engineers wont 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 werent even human footprints on Mars when the Chirpsithra came. If ever there are, theyll be around a Chirpsithra landing site. Passengers. Why would they give us an interstellar drive? We cant 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 Im 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 neednt 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. Its 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 Poseidons world. We would prefer to visit Poseidon before he dies. Wait but a moment. The Chirps monitor strip twinkled.
Herman took the opportunity to half-whisper, Weve been talking about water worlds. Thats Scylla. Nothing to trade, but supposed to be a poet. Poseidon lives on a water world not far from here. Hes 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 Poseidons 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 moments pause I asked, Whats 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 Scyllas snore rang out. Please show us this wonder.
Our monitorsbut you have a local computer, I see. The creatures long red armored hand reached out for the Beavers 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 Beavers equipment. Her fingers played over a surface. 
The Beaver was still attached; he twitched. The Macs 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 Chirps translator spoke. Roger Teng-Hui, how do galaxies form?
Teng said, Its 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. Its 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 hereeven Scylla, whose sea-locked kind breed transparent jellyfish to make ever more powerful telescopeswe 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.
Youve 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 yearswell. Some younger race might. Teng, Beaver, Rick, it is not in our interest that you should give up striving.
#
Scyllas 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, Lets 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. 
END

