In Carl Sagan's novel, Contact, Earth receives a message from extra terrestrial beings that has instructions to build a machine. Once the machine is built and activated with five passengers in it, they are taken through

several wormholes and finally reach their destination – the centre of the galaxy. Here they are told by the extra terrestrials that matter is being poured into Cygnus A. They are also told that there were even more ancient beings than themselves who have hidden messages in transcendental numbers.

Why could this information not be sent in the message itself without having to make mankind go through the trouble of building the machine?

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    Because building it and using it is proof.
    – Paulie_D
    Commented Sep 6, 2018 at 6:38
  • 1
    @Paulie_D, if that was their plan, it didn't work out too well. :-) What it did do, come to think of it, was attract global attention. A message about transcendental numbers probably wouldn't have done that, aliens or no aliens. Commented Sep 6, 2018 at 7:20

1 Answer 1


Much of the alien's purposes were explained in chapter 20. To pick out a few of the relevant points:

  • They wanted information they couldn't get just from distant observation:

"Don't think of us as some interstellar sheriff gunning down outlaw civilizations. Think of us more as the Office of the Galactic Census. We collect information."


"There was so much your television programs didn't tell us. Oh, we could figure out your technological level pretty well, and a lot more about you. But there's so much more to your species than that, things we couldn't possibly learn indirectly."

  • They wanted to help, something else that probably couldn't be achieved effectively without some level of direct contact:

"The [Hitler broadcast] was alarming. We could tell you were in deep trouble. But the music told us something else. The Beethoven told us there was hope. Marginal cases are our speciality. We thought you could use a little help."

  • Also, the Machine wasn't just a one-time deal: it allowed them to set up a permanent transit system to Earth, giving them the ability to observe more directly and, if necessary, intervene directly, though they considered that scenario unlikely:

"We think they did almost all the work." Vaygay was explaining his and Edna's theory on what the five of them had experienced. "All the project did was to make the faintest pucker in space-time, so they would have something to hook their tunnel onto."


"The Earth is linked up now, right? Both ways. If we can go home, you can come down to us in a jiffy. You know, that makes me awfully nervous. Why don't you just sever the link? We'll take it from here."

"Sorry, Presh." he replied, [...] "But we don't expect to use it."


They could arrive almost instantaneously, perhaps only in Hokkaido, perhaps anywhere on Earth. It was a transition to what Hadden had called microintervention. No matter what assurances they gave, they would watch us more closely now.

... but there's more to it than that. If all they'd wanted was to tell us about π, there would have been no need for the Machine, but by the same token, if all they wanted was for us to build the Machine, there'd have been no need for the Message to be so heavily obfuscated. This is one of those cases where it isn't so much about the destination as the journey. This is never explained in detail; the author deliberately leaves it as one more mystery. But it is heavily implied that it is all part of the alien's purpose, to help out a marginal but promising young civilization.

(Part of the purpose, however, may have been simply to attract attention. The drama around the Message, the controversy about whether or not to build the Machine, did undeniably attract the attention of all mankind, in a way that a message about transcendental numbers would have been unlikely to achieve.)

  • what an excellent response. Well, put. Commented Sep 6, 2018 at 14:35
  • could you add more details / fuller quote to the machine / link portion? Maybe I'm just conflating the film with the book (which I haven't read in ages), but I thought it was a one shot trip
    – NKCampbell
    Commented Sep 6, 2018 at 17:13
  • @NKCampbell, there's not a whole lot of detail in the book about that aspect, but I've added one relevant quote. I don't remember much from the movie, but I think you're right that it doesn't mention this. Commented Sep 6, 2018 at 19:49
  • The film definitely implies, if not outright states that the machine won't work again: "Do we get to come back? This was just a first step. In time, you'll take another. But other people need to see what I've seen... This is the way it's been done for billions of years." - springfieldspringfield.co.uk/movie_script.php?movie=contact
    – NKCampbell
    Commented Sep 6, 2018 at 20:08
  • @NKCampbell, in both the book and the movie it is made clear that there won't be a second trip. But in the book, at least, that's definitely a policy decision of the aliens, not a technological limitation. Commented Sep 6, 2018 at 21:26

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