In Doctor Who ("The Pandorica Opens" S05E12), River Song is the person responsible for leaving a message on "Planet One" carved into the Diamond Cliff.

The message reads:


River Song's message carved into the Diamond Cliff

Now, the "Hello Sweetie" is the obvious running greeting for River to The Doctor, and Long time fans know that "Theta Sigma" (ΘΣ) is a possible alias or name for The Doctor.

The remaining section is the part that I'm curious about;


With tones of science fiction programmes putting in codes for the audience to solve, does this last section have any perceived meaning?


2 Answers 2


For a possible explanation you'll have to consider the following:

  • The TARDIS translates (almost) everything so it can be perceived and understood by those travelling with it. This includes spoken and written words.

  • After this scene the Doctor notes that it's been a message and coordinates, so he travels to ancient Britain:

    Just followed the co-ordinates on the cliff face. Earth. Britain. one oh two am. No, pm. No, AD.

    Considering there's no other writing on the cliff (at least nothing seen by Amy and the audience), this has to be the information in the second line. However to me this creates a few new questions that can't necessarily be explained by what we see in the episode:

    • The characters appear to be of Greek origin, which doesn't make any sense (why weren't they translated as well? Or why were they translated into Greek?).
    • There are only 7 characters in 3 groups, making it impossible to include/encode all the information that's supposed to be in there. Remember that River knew exactly the point in time and space where the Doctor would arrive (sending the Roman soldier to welcome Caesar). So it's more precise than just "Britain 102 AD", but where is that information coming from?

What I think

It's possible to interpret the second line as Greek numerals:

  • ΘΣ: 9 200

  • Φ: 500

  • ΓΥΔϟ: 3 400 4 90

This doesn't sound that far off thinking about it - in fact it's my favorite theory right now. The information "on Earth" doesn't necessarily have to be included - neither does "to the Doctor", considering it's more or less River's home planet and it's clearly written by River. So with more specific details missing, it should be obvious she's talking about Earth.

The first two groups (ΘΣ Φ) could represent a coordinate pair to identify a specific point on the surface of the Earth and the last group (ΓΥΔϟ) would mark a specific point in time. Once again, there'd be an offset given by the fact the message is from River.

Edit [

Since I completely missed the clickable link regarding the Theta-Sigma reference, I skipped that. So here's an alternative interpretation with one more tiny assumption:

  • The first two Greek characters (ΘΣ) refer the Doctor as the intended recipient.
  • This leaves five more numerals for space and time (at least 3 dimensions).
  • Since there are only two groups, you'll have to add one more space that's omitted for whatever reason (might be a goof):

    • Φ: 500
    • ΓΥ: 3 400
    • Δϟ: 4 90
  • This doesn't sound that far off, because now the grouping makes more sense (the second and third coordinate being grouped, having a small number as well as a big one).

  • The question left is just how you could use those to get usable coordinates (longitude, latitude, and time).

  • This is pure speculation, but it makes sense in some way:

    • Let's just assume the Doctor's coordinates would work like humankind's longitude/latitude system, so Greenwich would denote 0°.
    • Since Stonehenge isn't that far away, I could accept the first number being the longitude, while the second number being the latitude.
    • Finally, the last number would denote the time, although this would still be rather rough given the fact that the Doctor seems to arrive just in time and not just within a general time frame (or it's just a rough estimate and the TARDIS would be able to determine the rest)? This would support the Doctor's confusion regarding am/pm/AD.
    • Since the Greek numerals don't make any direct sense the way they're used (they wer used in a decimal system), I could imagine this being based on a different scaling.
    • If you assume for time, the second digit to the right denotes 3 years rather than 10 years, you'd end up with 3 * 4 + 90 = 102... Eureka! Okay, it's really just speculation and trying to find a formula, which isn't that hard with only two numbers.


Although this still doesn't explain why the numbers don't show up using arabic numbers or anything more easily perceivable. Maybe the TARDIS isn't able to get the proper meaning (i.e. it doesn't know whether this is supposed to be words or numbers) or it's part of River's plan to hide the message right in the face of the whole universe to only be seen (and understood) by the Doctor.

  • 3
    Good answer :) And when it comes to the reason why they're using greek numerals it could be that it just takes less space than digits; it looks better (as in the writer and/or producers/director(s) wanted it this way); it's more mysterious (as most people will be wondering what it means), just like everything else when it comes to the Doctor; or it could be what the Doctor actually enters (however he does it) in the TARDIS when setting a destination in space and time, i.e. the TARDIS is only compatible with greek numerals and not digits.
    – Tom
    Commented Dec 22, 2013 at 18:33
  • Why do I sense a Kabbalist here :?) Commented Dec 23, 2013 at 4:41
  • The problem (from the question) is that Theta Sigma (ΘΣ) can't be part of the coordinates because it's theoretically a reference to the Doctor. But I'll take it as where and when. Not following why an offset because of River. Commented Dec 23, 2013 at 4:43
  • Yeah, I somehow completely missed that clickable link. So you'd have two groups of numerals. Still enough for some coordinates, but a bit short regarding 3D space (even if you consider time being the third dimension). However, it would make more sense with one space missing as a minor inaccuracy... updating my answer. :)
    – Mario
    Commented Dec 23, 2013 at 10:41
  • This answer is..fantastic! In all reality though, yes. I believe you are right about the coordinates and why the tardis couldn't translate it in particular :)
    – meer2kat
    Commented Apr 22, 2014 at 12:38

The ' symbol just after Theta-Sigma is the key to all the message. The Doctor knows he is being talked to directly. It is short for περισπωμένη.

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