Ben Bova

“ Pump in a modest amount of electrical power, excite a few trillion atoms, and out comes a coherent, pencil-thin beam of light that can be seen for millions of miles."
"Millions of miles aren't lightyears," Rizzo muttered.
"We're rapidly approaching the point where we'll have lasers capable of lightyear ranges. I'm sure that some intelligent race somewhere in this galaxy has achieved the necessary technology to signal from star to star—by light beams." ”

“ 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. ”

“ Rizzo snapped, sitting up on the bunk.
"What?"
"Binary code. To send a signal like this, they've gotta be able to write a message in units that're only a billionth of a second long. That takes computers. Right? Well, if they have computers, they must figure that we have computers. Digital computers run on binary code. Off or on ... go or no-go. It's simple. I'll bet we can slap that signal on a tape and run it through our computer here." ”

“ Rizzo rubbed a weary hand across his eyes. "Well, what do you think?"
"It's pretty obvious," I said. "They have the bombs. They've had them for quite some time. They must have a lot of other weapons, too—more ... advanced. They're trying to tell us their history with the equations. First they depended on natural sources of energy, plants and animals; then they developed artificial energy sources and built up a technology; finally they discovered nuclear energy."
"How long do you think they've had the bombs?"
"Hard to tell. A generation ... a century. ”

“ 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. ”

“ A long series of equations that bore repeatedly the symbols for many different metals came up next, followed by more on hydrocarbons, and then a string of formulas that we couldn't decipher at all.
This time it was my guess: "These look like energy-yielding reactions, too. At least in the beginning. But they don't seem to be naturally occurring types. Then comes a long story about metals. They're trying to tell us the history of their technological development—burning wood, coal and eventually oil; smelting metals ... they're showing us how they developed their technology." ”

“ I asked. "Think of the power it requires, and the likelihood that it's all wasted effort, because there's no one within range to talk to."
"Well ... it's worth a try, isn't it ... if you think there could be intelligent creatures somewhere else ... on a planet of another star."
"Hmph. We're trying to find another intelligent race; are we transmitting radio signals?"
"No," he admitted. "Congress wouldn't vote the money for a transmitter that big."
"Exactly," I said. "We're listening, but not transmitting."
Rizzo wasn't discouraged. ”

“ I asked, staring at the screen. "Where?"
THE END
[1] Astronomers have been able, since about 1910, to estimate the distances of Cepheid variable stars by timing their pulsations. The length of this type of star's pulsation is a true measure of its intrinsic brightness. Comparing the star's actual brightness to its apparent brightness, as seen from Earth, gives a good value for the star's distance. ”

“ Listen, the chances—just on statistical figuring alone—the chances are that there're millions of other solar systems with intelligent life. We've got to try contacting them! They might have knowledge that we don't have ... ”