But Rizzo wouldn't let up. "Suppose there's an intelligent race living
on a planet near a Cepheid variable star. They figure that any other
intelligent creatures would have astronomers who'd be curious about
their star, right? So they send out a laser signal that matches the
star's pulsations. When you look at the star, you see their signal.
What's more logical?"
"All right," I groused. "You've had your joke...."
"Tell you what," he insisted. "Let's put that one wavelength into an
oscilloscope and see if a definite signal comes out. Maybe it'll spell
out 'Take me to your leader' or something."
* * * * *
I ignored him and turned my attention to Army business. The
meteorological equipment was functioning perfectly, but our orders read
that one of us had to check it every twelve hours. So I checked and
tried to keep my eyes from wandering as Rizzo tinkered with a photocell
and oscilloscope.
"There we are," he said, at length. "Now let's see what they're telling
us."
In spite of myself I looked up at the face of the oscilloscope. A
steady, gradually sloping greenish line was traced across the screen.
"No message," I said.
Rizzo shrugged elaborately.
"If you leave the 'scope on for two days, you'll find that the line
makes a full swing from peak to null," I informed him. "The star
pulsates every two days, bright to dim."
"Let's turn up the gain," he said, and he flicked a few knobs on the
front of the 'scope.
The line didn't change at all.
"What's the sweep speed?" I asked.
"One nanosecond per centimeter." That meant that each centimeter-wide
square on the screen's face represented one billionth of a second.
There are as many nanoseconds in one second as there are seconds in
thirty-two years.
"Well, if you don't get a signal at that sensitivity, there just isn't
any signal there," I said.
Rizzo nodded. He seemed slightly disappointed that his joke was at an
end. I turned back to the meteorological instruments, but I couldn't
concentrate on them. Somehow I felt disappointed, too. Subconsciously,
I suppose, I had been hoping that Rizzo actually would detect a signal
from the star. _Fool!_ I told myself. But what could explain that
bright emission line? I glanced up at the oscilloscope again.
And suddenly the smooth steady line broke into a jagged series of
millions of peaks and nulls!