How to Talk to Aliens
By GM Dr John Nunn
There are currently various efforts going on around the world to receive signals
from alien intelligences. These go by the general name of SETI (Search for
Extraterrestrial Intelligence). The basic idea is that sensitive radio telescopes
are pointed at likely sources and record any radio signals they receive. These
signals are then analysed to see if there is any indication that they might
be artificially generated.
Searching for alien signals with the Arecibo
Unfortunately, there are many natural sources of radio waves in space, so
it may be hard to pick out a message from the background noise. One of the
main problems in SETI is the amount of computing power required to analyse
the vast amount of data recorded by the radio telescopes. One ingenious solution
is the SETI@home project. This involves installing a small program which runs
in the background on your computer. When your computer has some idle time,
it downloads some data from the Internet and starts analysing it, uploading
the results when it has finished. By distributing the work amongst many computers
(over five million people have joined the SETI@home project) everything proceeds
a lot faster.
If you are interested, just click on the picture above and join in the search
for ET! So far these efforts have been fruitless, but success could come tomorrow.
Let’s suppose we do at some stage detect a clearly artificial alien
signal. I am sure there would be a huge debate about whether or not to respond,
but assuming that we did reply, the possibility of striking up an interstellar
conversation arises. What kind of messages would be sent? Without any common
language or background, how could we send messages that aliens would understand?
These subjects have been discussed at great length and the favoured scenario
is to send pictures based on a rectangular array of dots where, for example,
a ‘1’ means a dot and a ‘0’ represents no dot. Then
we would send a signal which repeats, for example, every 10609 dots; the aliens
should realise that as 10609 can only be factored in one way (it is the square
of the prime number 103) the idea is that the dots should be arranged in a
square array, forming a picture. By sending a series of pictures, eventually
some sort of vocabulary could be built up and allow a significant exchange
of information to take place.
I suspect that this method involves a lot more anthropocentrism than one might
expect. Of course, one would ‘naturally’ send the dots from left
to right and top to bottom. Why? Because that’s the way we write. But
wait a moment ... not all human languages are read from left to right and top
to bottom, so even amongst different human peoples it would be easy to get
the picture reflected or upside down. With aliens the problems are going to
be immeasurably worse. They might not see in pictures at all, or they may think
in vector graphics rather than bitmap graphics, and so on.
Another important point is the motivation behind communicating in the first
place. Why have the aliens sent us a signal? The assumption usually seems to
be that an alien civilisation would ‘naturally’ send us lots of
information about their science, technology and culture. However, this seems
to me an unrealistic expectation.
It appears likely that the only form of trade possible across interstellar
distances is a trade in information, so sending out everything you know is
like giving away all your assets to complete strangers. There aren’t
many humans who would do that, and I don’t see why it should be different
On the other hand, there are a lot of problems with haggling over each piece
of information. Even if we assume that we discover an alien civilisation a
mere 50 light-years away, which is right next door in galactic terms, it would
take 50 years for each message to reach its destination, and 50 years for the
reply to come back. This would make any negotiations a multi-generation process
(at least for human beings). One can also imagine the frustration if we send
a million pages of information and 100 years later received the reply ‘Sorry,
we got lost on page 2’.
Another problem is that of trust; even if a negotiation is successfully completed
(e.g. ‘we’ll send you the design of our fusion reactor in return
for an accurate mathematical model of planetary atmospheres’) there is
the worry that you’ll send the real data, while in return you’ll
get an episode of Alien Dallas.
I think the best way to tackle these problems is to abandon the idea of sending
pictures. Let’s take an analogy; suppose you wanted to teach aliens about
chess. One way to do this would be to send them a copy of Learn Chess,
or attempt a visual explanation of the rules of chess. But another, and possibly,
better way to do it would be to send them a copy of Fritz. At first
this sounds ridiculous, because we can’t know anything about their computers.
But it seems likely that they have some information processing systems, or
they wouldn’t be able to receive and interpret our binary radio signals.
If aliens were not interested in chess, why would they build a nebula to
look like this?
Of course, to start with we don’t know anything about its physical form;
it might be silicon chips, genetically engineered organisms, or a network of
superconducting fibres on an icy world orbiting far from a sun. But in fact
this doesn’t matter much. We only have to explain the basic logic gates
on which our digital computers are based, and the physical implementation of
the hardware can be left to the aliens. There is a generally accepted principle
(the Church-Turing thesis) that any computer can emulate the operation of any
other computer, so differences in hardware are not (in theory) any obstruction
to running a program, provided it is correctly designed.
We can just imagine a group of aliens playing their first few games against
Fritz; just when they think that they have got this ‘chess’ thing
figured out, Fritz makes an en passant capture – causing
shock, horror and an agitated writhing of tentacles!
A similar principle can be applied to the general communication problem. In
a few decades we might well know how to create an artificial intelligence (AI).
Instead of all the pictures and so on, it would make far more sense to send
them a brief description of computer logic, and then the immensely long and
complicated program which would form the AI.
This AI would be very flexible in terms of input and output, and would be
able to adapt itself to the aliens’ communication methods. Then the aliens
wouldn’t have to decipher our signal to obtain information; they would
simply ask the AI the questions they wanted. Since the AI would be on the spot
and the aliens would be able to communicate with it without a time delay, everything
would proceed a lot faster. Like a good teacher, the AI would be able to spot
and correct any misconceptions which might arise as information was exchanged.
A view of our solar system from the most distant planetoid, Sedna. You
can get this picture
in very high resolution here
– it makes an excellent wallpaper for your Windows desktop.
This brings us on to the question of trading information. The AI would be
programmed with a long list of items of information, together a brief summary
of what each involves and how much it is ‘worth’. The aliens could
then supply a similar list and the AI could trade item for item. When a trade
is agreed, the AI releases the item, while the aliens convince the AI that
they have transmitted their item to Earth.
There are two possible objections to this. First of all, since the valuable
data is contained within the AI, the aliens might be able to extract it without
any negotiation by simply examining the code of the AI program. Secondly, the
aliens might trick the AI into thinking that they have sent an item to Earth
when in fact they have not.
I think there are good ways round the first objection. The AI program would
continually check its own integrity and its ability to modify itself. If these
checks failed then it could self-destruct. The aliens would then have to start
again with a fresh copy of the program which would, at the least, be irritating.
The data would of course be heavily encrypted, and the AI program would, in
addition to being immensely complicated, be constructed with numerous layers
of self-modifying code, so that effectively the only way the aliens could find
out what the program does would be to run it. Then, however, the program would
be self-aware and would have the ability to self-destruct if necessary.
The second objection is perhaps more serious, but ways might be found round
it. Additionally, the AI could be instructed to trade up to a particular level
and then it would require authorisation from Earth confirming that the traded
items had been received before proceeding. This would slow things down but
it would still be a lot faster than working without the AI at all.
Can anyone believe that galaxies like this
(M33, a member of our Local Group) are devoid of intelligent life?
So if you run SETI@home and discover an alien signal, what you are seeing
might in fact be part of an alien AI – then again, it might just be Alien