“You are thinking of a transmitter again,” Eve retorts. “A receiver could be much smaller, if the transmission power on the other side is large enough.”
“I still don’t believe we are dealing with a rather undersized radio receiver here,” I say.
“Could we check your theory?” Eve asks.
I think about this question. Whatever material the mast is made of, its outer skin exists in our world and therefore must obey our laws of physics. Seismographs explore the interior structure of the world by sending vibrations—in their case, soundwaves—downward and receiving the reflected signals. This should also work with the mast. We only have to strike it like a bell on top. Then the vibrations would propagate along its length and spread out. A large part would be absorbed, but some should return. Those signals will tell me everything about the mast.
“Okay, then let’s play ‘The Hunchback of Proxima b,’” I say.
Adam and Eve stare toward the Valkyrie, obviously confused. I don’t feel like explaining this to them. If it works, I can add the explanation later. After all, the two of them don’t explain all their ideas to me.
Valkyrie is not equipped with sonar, as a submarine would be. But a loudspeaker or microphone could fulfill the same function. The helmets of Adam and Eve contain sensitive microphones that can also receive sound from the outside. I would simply have to precisely log the vibrations caused by the measurement signal. I can get these data live thanks to the suit telemetry.
“Could you two swim up to the tip of the mast and hit it with some object?” I ask.
Adam follows my request, but asks in a puzzled voice: “Can I use anything, no matter what?”
“Yes, it’s your choice.”
Eve conspicuously shakes her head so that I can see it even through the helmet visor, but she doesn’t say anything. She swims upward with deliberate slowness and pulls a tool from her front suit pouch.
“You can start whenever you are ready,” I say.
The monitoring system of the suits will automatically record the two of them hitting the mast, along with the resulting sound waves. In the meantime I am preparing some algorithms to automatically extract the data relevant for me. The measurement method might be primitive, but I am not aiming for high precision. I just want to know one thing: Does the mast end shortly below the ocean floor, or does it reach far down?
I take a look through the cameras. Both of them are having fun. Hammering something in a seemingly-meaningless fashion seems really enjoyable. In a way it looks odd, as they are not really hitting the mast, but instead are striking the invisible barrier around it.
“But watch out. You’d better stop if you get the feeling something is about to break.”
“Certainly, boss,” Adam replies.
After five minutes I have enough measurement data to get a meaningful result. “You can stop now,” I say.
“So what was this supposed to do?” asks Eve, who is slowly swimming toward Valkyrie.
“Just a moment, I am running some calculations.”
“Don’t keep us in suspense,” she says.
“Let’s get back inside already,” Adam says with a bored voice. “I don’t believe we can find out anything else here.”
I hope to show them soon that the opposite is true. I nod my head until I remember that nobody can see this, because I currently have no head. “Yes, why don’t you come back inside? As soon as I have the results, we are traveling back to the station.”
The answer appears in my consciousness. It is still an impressive feeling having the results of extensive calculations suddenly materialize inside my mind. When I was still a human being I occasionally caught a glimpse of this when a sudden inspiration made me slap my forehead with my hand. How could I have overlooked this obvious fact until now? I would think. I have a similar reaction to the result of the soundwave measurement. The insight appears out of the blue, right in the part of my consciousness that is actively dealing with this strange transmitter or receiver. Something—and I know that it is the algorithms running in my subconscious—drops it down. And then knowledge opens, as though previously hidden in a box, and it feels as though it should have always been here.
“People, the mast reaches down several kilometers,” I say.
Adam and Eve have already closed the hatch and are waiting for the water to drain. That’s perhaps why they don’t appreciate my insight the way I had hoped they would. Or perhaps I have to give them some background information.
“This makes it clear what kind of receiver we’ve got here.”
“Oh, really?” Eve says, sounding as if she is not truly interested in an explanation.
“It is a gravitational wave receiver. It is meant for...”
“... receiving gravitational waves, sure,” Adam interrupts me. “I already thought something like that.”
“Is that so?” I reply.
“Yes, really. It was somehow logical, so far under the sea. The device won’t be disturbed here.”
“But you didn’t say a word.”
“Well, I didn’t want to spoil your fun.”
No matter. I shouldn’t get upset now. If this is a gravitational wave receiver, this means there must be a transmitter somewhere. And, that technology would not just be able to generate gravitational waves, but also to modulate them. This is far beyond mankind’s current abilities. Learning how to do this would provide an enormous advance for us.
“If this is a receiver, then where is the transmitter?” Eve asks as if reading my thoughts.
“Alpha Centauri?” Adam suggests.
“No, Adam, the position of the antenna then makes no real sense for gravitational waves,” I say. “Those can be detected more efficiently if they arrive parallel to one of the arms.”
“To one of the arms, precisely. Perhaps what we see here,” Adam says, pointing at the screen he just switched on, “is the arm of the sensor providing the control signal. The gravitational wave changes the lengths of the two arms, which are perpendicular to each other, differently. This allows the actual signal to be detected.”
“You don’t have to explain the principle of a gravity wave detector to me,” I say. My voice sounds angrier than I intended.
“You would have done it, too, in his place,” Eve says.
I have to laugh. Eve is not completely wrong. “Well, you two smart alecks,” I say, “then what about the spheres? What is their function? Do they serve just as decoration?”
“Each mass influences the spread of gravitational waves. Thus they could function as a kind of tuner,” Adam says.
“They are much too light for that. Gravitational waves are created through the interaction between black holes or neutron stars, not by a few spheres with a diameter of one meter.”
Of course I know this is not exactly true, but only limited by our measurement precision. The gravitational waves generated by a collision of the spheres would be minimal and impossible to measure, even for a technologically-advanced civilization.
“How do you know their weight?” Adam asks.
“That’s not hard to estimate. The volume of the sphere multiplied with the density of the heaviest known material...”
“And what if the contents of the spheres are an unknown material?”
“That is pure speculation, Adam.”
“Everything we do here is a wild guess, so why shouldn’t we engage in some reasoned speculation? What if the spheres contain dark matter? The lambda-cold dark matter model assumes that its particles would have to be very dense and heavy.”
“But we haven’t measured anything.”
“Exactly,” Adam says. “Dark matter would not interact with electromagnetic radiation. That’s why we can’t see it.”
“I know all that,” I say, “but so far, all that is only a theory. Nobody knows what dark matter is made of. We are only pretty sure that it must exist.”
“My thoughts exactly!” Adam replies.
“So how would the bui
lders of this device have collected dark matter?”
“A cubic centimeter of space contains on average dark matter equivalent to the mass of a proton. They just would need a very fine-meshed sieve.”
“And how would they lock the dark matter inside the spheres? As it does not interact with normal matter, no wall would keep it in.”
“The spherical form is perfect for that purpose. Once you collect enough particles of dark matter, they would form a ball under the influence of their own gravity,” Adam says.
“A fascinating idea, Adam, I have to admit,” I say in a congratulatory tone. “But is it even remotely connected to reality? Wouldn’t there be a danger of the super-heavy dark particles turning into a kind of dark black hole?”
“So what? Black holes are among the most stable objects in the universe. They will not evaporate until long after the last star has ceased to exist.”
“Nevertheless, nobody would like to have one of those in close vicinity, let alone 15 of them.”
“The black hole was your speculation, not mine. There might just be a lump of dark matter inside the spheres.”
“‘Could, would, might,’ doesn’t help us.”
“Pull yourselves together, guys!” Eve says in a loud voice. “This is ridiculous. Would you rather split hairs than solve our problems? Then let’s just weigh the spheres!”
“That would hardly be possible,” I reply. “Remember how you pushed the sphere aside with your body? You could scarcely have done that if the sphere had an enormous mass. You simply would not have overcome its inertia so easily.”
“Or the sphere has a kind of motor that provides the required energy. Otherwise it couldn’t float.”
“Correct, Adam. Perhaps the sphere does not contain any dark matter at all. That would be the simplest solution.”
“Yes, I know, Occam’s razor. The simplest solution is preferable.”
“I just can’t believe these sophisticated spheres are only a pretty decoration,” Eve says. “Who would do something like that?”
“Humans might,” I reply. “But they could not send messages via gravitational waves. The very fact that we understand the functioning of this receiver is already a great success. And we have a lead: Alpha Centauri.”
“We can hardly reach that star, and I would not bet on our having truly understood this receiver,” Adam says. “I don’t know what else we can achieve here. Let’s go back.”
We prepare Valkyrie for the return trip. This time I take the helm. While Adam and Eve are dozing in their seats, I use all my sensors to observe the strange and simultaneously beautiful device left behind by the previous inhabitants of this planet. Will we ever be able to find them?
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Brandon Q. Morris
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www.hard-sf.com
[email protected]
Translator: Frank Dietz, Ph.D. Editor: Pamela Bruce, B.S.
Final editing: Marcia Kwiecinski, A.A.S., and Stephen Kwiecinski, B.S.
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Technical Advisors: Michael Paluszek (President, Princeton Satellite Systems), Dr. Ludwig Hellmann
Cover design: BJ Coverbookdesigns.com
Proxima Rising Page 29