How the Hell That All Works
"And if you don't hear ET there? Well, tough toe-corns."
Mark: Now, I imagine there must be many, many false alarms. Things that are
picked up and determined to be background noise, anomalies, perhaps galaxies
emitting natural things that while they have patterns, they're not signs of
intelligent life. How do you determine whether a pattern is background noise
or a signal?
Seth indicates where the ay-leens come from
Seth: Yeah, well, this is a question we get asked a lot—"Do you have a
cryptologist or a cryptographer sort of looking at these things to say, well,
this looks natural, that looks artificial?" In a way we do, although we
really don't. We don't have any cryptographer. We can barely afford to have
someone just clean up the rooms. The way it's done is, the nature of the
signal itself is the decryption. If it's a narrow-band signal, that's
something that's really easy to build a transmitter to make, but that's
extremely difficult for nature to make. Nature doesn't make narrow-band
I mean, listen to quasar with a radio telescope and you hear "PSHHHHH." It
almost doesn't matter where you turn your knob, you'll hear that blank noise
'cause it's all across the band. Even if you listen to a pulsar, pulsars go on
and on, maybe a thousand times a second, faster in some cases. But what you
hear is "PRRRRR" or "PSH-PSH-PSH-PSH-PSH." It's still white noise. It doesn't
matter where you're tuning your radio. You'll hear the pulsar, you see. Tune
across a wide, wide range of frequencies and you still hear "PSH-PSH-PSH." So
that's clearly nature because nature doesn't care about wasting a lot of
energy. No person who was designing a transmitter would build one that sent
ten pulses a second all over the band. It's a total waste of energy; it's bad
So that's how you do it, you say, "Hey look, if they put all the energy into a
small region of the dial, that's something nature never does but transmitters
do all the time." So that's how you tell.
Mark: Now, have we scanned the entire spectrum?
Seth: No, not by any means. We have only looked at a tiny fraction of the
radio spectrum. Our experiment, Project Phoenix, which is run by the Institute—[pointing
to a photograph on the wall] that antenna, the one in the middle—looks
at more of the spectrum than any other experiment ever has. It's
looking over from 1,000 to 3,000 megahertz. Each channel is about 1 Hz wide so
that's like 2 billion channels for each star that we look at. That's still not
the whole spectrum.
Mark: This is actually a question that came from one of our contributors. I
don't know if it was Paul or Zach. They were under the impression that the
signals are scanned for 300 seconds, approximately?
Seth: Yeah, that's about right.
Mark: How do you determine which bands to target first?
Seth: Oh, well, we just start at the bottom of the band and work up. How are
you gonna know. If you start at the bottom of the band you may miss ET's
transmission at the top of the band, yeah, but maybe if you start at the top
of the band you'll miss his transmission at the bottom of the band. You don't
have any information about that so you just—it's a matter of being
methodical. We always do it the same way. Start at the bottom of the band and
work up. It takes, you know, about ten to twelve hours to go through all those
frequencies for any given star.
Mark: Yeah, but how much information is captured in that five minute window?
Seth: Well, in a five minute window you're listening to 28 million channels.
So you're getting information about 28 million, actually, it's 56 million
channels. It's 28 million frequency channels, but the receiver has—there
are two polarizations that you're actually sensing, so there are actually two
receivers in one at the focus, so it's actually 56 million channels. So during
that five minutes you're looking for signals that are within those 28 million
frequencies. And if you don't hear ET there? Well, tough toe-corns, move up
and do 300 seconds on the next batch of frequencies. No ET? Go up the dial a
little bit and do more, and that's the way it's done. And actually, observing
one star isn't done at once, it's done in pieces, over the course of a couple
Siduri: I believe Paul's exact question was, "Ask how the hell that all works."
Seth: How the hell that all works. Well, what didn't I answer?
Mark: Perhaps you could start by telling us, once the data is collected by the
telescope, where does it go? The project has been going on longer than hard
drives have been in common use to store this data.
Mark: Does it get printed out onto paper reels?
Seth: In the old days it was printed out on paper, yeah, it was. Not anymore.
Those were the good old days. You could come in and there was only one
channel, or ten channels, or some small number of channels, a hundred
channels. So it was possible to put all the data out on a, usually a line
printer. In the very earliest experiments it was just a strip-chart report.
You know, one pen on a piece of paper. Maybe two, if you had two pole
positions. When Frank did the first experiment in 1960, that's the way it was
done. He just had a little motor that essentially turned the knob on the
receiver and turned it up and down the dial, very slowly, you see, so the
frequency was changing. And you could just look at the output. And he had a
loudspeaker connected to it. It was all very simple. And then ten years later
you could look through a hundred channels at once, so then you needed a line
That was what was being used in 1977 at Ohio State, when some guy came in in
the morning looking through the stack of computer printout, and saw one big
signal and said "wow!" Wrote WOW next to it. The Wow Signal.
Mark: Can you talk a little bit more about that?
Siduri: Yeah, whatever happened to that?
Seth: Yeah, the wow signal. Well, it's pretty wow-y. But it doesn't seem to
have been ET. Lots of people have gone back and they even, they immediately
had a following beam on the sky that swept through that same patch of the
heavens, just shortly after they got that signal, and didn't see it. And
people have gone back there looking, you know, with more sensitivity, more
frequencies, and nobody's ever found it again. So it's not good enough. It's
like seeing a ghost in your basement once. It's not enough to believe in
ghosts. If you see them every time you look, now that's okay, you might
believe then. So it was undoubtedly some sort of interference.
Siduri: Is that the closest you've ever come to finding...
Seth: Well, how do you know? That's like pregnancy, I mean, are you close?
It's not a matter of close, it's yes, it's a one-bit experiment. It's not that
you're close. There have been lots and lots of false alarms. Particularly in
the early days, because in the early days you would usually report the data.
As you said, it was before hard disks. But what would happen is that you would
go the telescope and you had a hundred channels, and normally you would just
write everything to computer tape. Back with these big tapes, and you would
put them on computers wherever you were, and play 'em back, and then look at
all the data.
And you'd always find signals. You've got these huge antennas, you know, with
very sensitive receivers, and hundreds of channels, thousands of channels, and
now millions of channels, so of course you found signals. But then what did
you do? What do you do with them? You could call up the local papers and say,
"By the way, I found all these signals," and that would work the first time.
But, well, how do you know it's ET? And you say, "well, I don't know." Then
the next time you went back to Tucson you'd try to look at those parts of the
sky again. And that's very tedious.
But now, what we do, is we check out all the signals right away, in real time.
All the data's processed real time. So you don't leave the telescope with a
stack of mystery signals. You know each one of them because you tracked it
down. So in the early days there were lots and lots of these sorts of false
alarms. Not anymore.
Mark: Does that mean that the sensitivity to signals may be less now than it was
Seth: No, the sensitivity's clearly better now. The sensitivity's better but
the processing's better. That's just because, you know, digital electronics is
better than it was. So now you can conceivably process everything in real
time. That's the way it's done. When you're sitting down there in Puerto Rico,
you're sitting at the control room, and the signals are coming in about—you
get hundreds of signals every night. Hundreds. And each one of them is checked
out. So far each one of them has been us.