One Thing You Always Need
Siduri: Well, I was gonna say, I have a list of softball questions from your
biggest fan, and then I have a list of hardball questions. And one of the...
Seth: The softball questions are from my biggest fan? Is that my mom?
Siduri: No, I told you that there's a guy on the list that was a big fan of
yours, and was all but asking for your autograph. And so I have a list of
questions from him...
Seth: I hope he's not a Czech. [I think that's what he said. He was muttering
Mark Territory: From Scotland?
Siduri: Uh, yes.
TCS: Paul from Scotland?
Siduri: Um, he's just seen you I think, on like, radio shows.
Seth: Seen me on radio shows.
Siduri: Or, heard you on radio shows.
TCS: Heard you on TV. [Everyone's talking at once. I'm not sure this was what
Mark: Might be a stalker, I don't know.
Siduri: But he's in Scotland, so I don't think you have to worry about him. But
anyway, so one of the hardball questions was: "Our own civilization has only
been using radio to transmit messages for less than a hundred years. Now these
messages are increasingly being delivered in a digital, often encrypted form
that is practically indistinguishable from white noise. What sense does it
make to search the radio spectrum for such old-fashioned messages that we
ourselves have only bothered using during this brief window?"
Seth: Good question, Paul.
Siduri: No, that wasn't Paul. That was Zach.
Seth: Good question, Zach. Next question.
No, no, no, he was absolutely right. I mean, if you look at the kind of
signals that we're currently using, sort of spread-spectrum signals and things
like that, they're very complicated, and they're completely unlike the kind of
things we look for in SETI. The kind of things we look for in SETI are signals
that are just what are called narrow-band signals, that are on one spot on the
radio dial. So they take all the energy of the transmitter and pump it all
into one small frequency range. Okay? You with me?
Seth: All right. The advantage of that is that it makes it really easy to find
the signal because all the energy is in a small band so it really stands out
as a big spike of energy. Whereas if you spread it out over five megahertz,
like a TV signal, then the energy's spread all over the band and it's very
hard to find. But on the other hand, the actual signals that we use are spread
out, more and more. And ET will be at least as advanced as we are, so you
might say, "Well, why would they make those narrow-band signals?"
And the answer is, probably: most of the time, they don't. For their own
internal communications they probably wouldn't do that. But if you have a
beacon, which you want to hear at great distance—if for some reason they
want to get in touch, or they're sending the galactic weather report,
whatever, GPSs—there's lots of things that would have narrow-band
components in the signal. So that's what we look for. But Zach has a point.
Siduri: So the assumption is that they would have to be kind of trying to get in
Seth: They might have to be trying. Or, I'm not sure I would even go that far.
If you asked Marconi a hundred years ago, what would he think the radio
signals would be like in the year 2001, or whaddya think people will be using
this technology for in the year 2001, he wouldn't have had a very good idea.
He probably wouldn't have gotten it right—not much of it, anyway. So for us
to say what kind of signals ET uses, a hundred thousand years ahead of us,
what kind of signals he's producing—you could guess if you want. Probably
not a very good guess.
I mean, one thing you always need is high-powered radar to look for incoming
comets. Long period comets. Cause they can come in, and as you know, ruin your
whole day. Land in Yucatan. But I mean, he has a point. It's just that we're
looking for the signals that are easy to find.
Mark: Are we also looking for the signals that might be accidentally broadcast?
Seth: Yeah, well, that's the question, and
that's the question that Zach is
really asking. And Shannon jumped to the conclusion, as she is wont to do,
that we can only pick up deliberately broadcast signals. But you don't know
what ET's using radio for, so...
Siduri [jumping to a conclusion]: ...We could happen on something.
Seth: Yeah, we could trip on, as I say, a radar that they're using to warn
about incoming Klingons, if you don't like radar warning about incoming
comets. And in that case, then...
Mark: We'll get to those questions later.
Seth: And then you can say, "Well, it wasn't deliberate, but we got it
anyhow," see. So in a sense SETI doesn't care. Yeah, what do we care.