"The rest is technical," said Duncan, switching off the recording. "I merely wanted you to hear what the Iapetus survey team brought home with them. And it's something that could never have been picked
up inside the orbit of Saturn."
A voice he had not heard before — young, rather self-assured — came out of the air behind him.
"But this is all old material, familiar to everyone in the field. Sandemann and Koralski showed that those signals were almost certainly relaxation oscillations, probably in a plasma cloud near one of Saturn's Trojan points."
Duncan felt his façade of instant expertise rapidly crumbling; he should have guessed that there would be someone in his audience who would know far more about his subject than he did — and possibly, for
that matter, even than Karl.
"I'm not competent to discuss that," he replied. "I'm only reporting Dr. Helmer's opinions. He believed that there was a whole new science here, waiting to be opened up. After all, every time we have explored some new region of the spectrum, it's led to astonishing and totally unexpected discoveries.
Helmer was convinced that this would happen again.
"But to study these gigantic waves — up to a million times longer than those observed in classical radio astronomy — we must use correspondingly gigantic antenna systems. Both to collect them —
because they're very weak — and to determine the directions from which they come.
"This was Karl Helmer's Argus. His records and sketches contain quite detailed designs. I leave it to others to say how practical they are."
"Argus would look in all directions simultaneously, like the great missile-tracking radars of the twentieth century. It would be the three-dimensional equivalent of CYCLOPS — and several hundred
times larger, because it would need to be at least a thousand kilometers in diameter. Preferably ten
thousand, to get good resolving power at these ultralow frequencies."
"Yet it need contain much less material than CYCLOPS, because it would be built in Deep Space, under weightless conditions. Helmer chose as its location the satellite Mnemosyne, outermost of Saturn's
moons, and it seems a very logical choice..."
"For Mnemosyne is twenty million kilometers from Saturn, well clear of the planet's own feeble
ionosphere, and also far enough out for its tidal forces to be negligible. But most important of all, it has almost zero rotation. Only a modest amount of rocket power would cancel its spin entirely. Mnemosyne
would then be the only body in the universe with no rotation at all, and Helmer suggests that it might be an ideal laboratory for various cosmological experiments."
"Such as a test of Mach's principle," interrupted that confident young voice.
"Yes," agreed Duncan, now more than ever impressed by his unknown critic. "That was one possibility he mentioned. But back to Argus..."
"Mnemosyne would serve as the core or nucleus of the array. Thousands of elements — little more
than stiff wires — would radiate from it, like — like the spines of a sea urchin. Thus it could comb the entire sky for signals. And incidentally, the temperature out around Mnemosyne is so low that cheap
superconductors could be used, enormously increasing the efficiency of the system."
"I won't get involved in the details of switching and phasing that would allow Argus to swing its antenna spines electrically — without moving them physically — so that it could concentrate on any
particular region of the sky. All this, and a great deal more, Helmer had worked out in his notes, using techniques evolved with CYCLOPS and other radio telescopes."
"You may wonder — as I did — how he ever hoped to get such a gigantic project started. He planned a simple demonstration, which he was certain would provide enough evidence to prove his theories."
"He was going to launch two equal, massive weights in exactly opposite directions, each towing a fine wire, several hundred kilometers long. When the wire had been completely deployed, the weights would
be jettisoned — and he would have a dimple dipole antenna, perhaps a thousand kilometers long. He
hoped that he could persuade the Solar Survey to do the experiment, which would be quite cheap, and
would certainly produce some results of value. The he was going to follow it up with more ambitious
schemes, shooting wires out at right angles, and so on..."
"But I think I've said enough to let you judge for yourselves. There's much more I've not had time to transcribe. I hope you can be patient, at least until after the Centennial. For that, as you are well aware, is what I really came for — and I have work to do..."
*
*
*
*
*
"Thank you for your moral support, Bob," said Duncan, when he and His Excellency the Ambassador for Titan had emerged into the bright sunlight of Virginia Avenue.
"I never said a word. I was completely out of my depth. And I kept hoping that someone would put
the question I'm still anxious to see answered."
"What's that?" Duncan asked suspiciously.
"How did Helmer think he could get away with it?"