The Yrr’s solution to a set of mathematical problems becomes the first compelling demonstration that the Scratch signal can carry a deliberate reply. The team’s exchange does more than confirm that an unknown intelligence has heard them: the pattern of the answer reveals an image of their own ship, seen from below the surface. In one movement, an obscure ocean signal becomes communication—and the human vessel becomes an object represented by another intelligence.

From Scratch to a test

The team does not begin by claiming that it understands Scratch as the Yrr use it among themselves. Samantha Crowe makes a distinction between the signal’s possible status as a language and the particular form in which it has been encoded. Its structure resembles the Arecibo message: humans do not normally speak in binary, and the earlier message was sent by computers. The signal’s format may therefore be a constructed means of communication rather than a transparent sample of ordinary speech. Crowe also acknowledges that the team cannot make sense of earlier Scratch signals. What they have, she argues, is something more decisive: contact.

Murray Shankar and Crowe explain how the team approached the signal’s physical form. Scratch sounds like a needle dragged across a record, but its underlying signal is a staccato vibration at very low frequency, suited to traveling long distances through the ocean. Because such infrasound is normally below the range of human hearing, it must be accelerated to become audible; speeding it up, however, also speeds up its pulses and obscures their structure. The researchers instead slowed the recording, stretching the signal until its scratching texture resolved into individual pulses of different lengths and intensities. The change in playback turns what first sounds like noise into a sequence that can be examined for components.

The team’s experiment is deliberately simple. It sends mathematical exercises asking the recipients to continue decimal sequences, solve logarithms, and supply missing numbers. The questions are intended as a test of whether the Yrr have heard the transmission and can manipulate numbers, not as an attempt to translate the full language of Scratch. The method makes the response legible through a shared formal system while leaving the wider workings of Yrr communication unresolved.

The answer in the numbers

When Shankar displays the reply, the screen shows rows of figures, with some columns apparently identical. The results are exact: the Yrr have answered every problem correctly. Karen Weaver reacts in a whisper, while the others look at the figures with a mixture of admiration and fear. Their response is not merely a signal that something exists nearby. It demonstrates that the sender has received the test and produced its correct solutions.

Crowe draws a further conclusion from the exchange. The reply indicates that Scratch can function as a language carrying complex information, and, more importantly, that the Yrr can adapt it so that humans can understand what they are communicating. They have decoded the human questions and coded an answer of their own. Crowe treats this capacity to move between systems as evidence that the Yrr are as intelligent as humans, rather than merely emitting a signal that happens to be detectable.

That interpretation is not accepted without qualification. Sigur Johanson challenges the leap from symbol manipulation to higher intelligence. He points out that a creature may perform a complex operation without understanding it: a chameleon’s color change can involve sophisticated processing without implying that the animal conceptualizes the code it appears to use. Crowe agrees that correct answers alone do not settle the question. The episode therefore makes the test’s limits part of its meaning: calculation proves successful exchange, but the team still needs evidence that the Yrr can connect symbols to conditions in the world.

A pattern becomes an image

Crowe directs attention to the arrangement of the answers, not just their correctness. The two solutions recur in an apparently irregular sequence: one answer appears eleven times in a row, another appears three times, and later the second recurs nearly thirty thousand times. Repetition could help make a transmission long enough to detect, but the mixture of the two answers suggests that the sequence may have another function. The numerical reply is itself organized as a code.

Shankar converts that arrangement into an image of black and white pixels, using an approach associated with messages examined by SETI. The image initially resists recognition. Jack Vanderbilt wonders whether it shows a fish or a huge animal; Judith Li identifies the background as waves and explains that the view is a snapshot from below, looking toward the surface. The dark shape is their ship. What looked like an unexplained arrangement of repeated mathematical answers is thus revealed as a representation of the human vessel, seen from the depths.

The image changes the terms of the encounter. The Yrr have not only solved a human-designed test; they have used its results to construct a visual message that identifies what they can see. Their reply presents the ship from a vantage point opposite the researchers’ own: the humans look down through the ocean, while the image looks upward from beneath the surface. The sea is no longer simply the medium carrying a signal. It is the space from which the Yrr observe and depict the people trying to reach them.

The significance and limits of contact

The episode moves through several thresholds of knowledge. At first, the researchers can isolate pulses but do not know how Scratch works in its ordinary use. The mathematical test then establishes that a reply can be elicited and checked; the repeated-answer pattern reveals that the reply contains a second, visual code. Each step makes the signal more intelligible without making the Yrr’s full language or consciousness transparent. The ship image is a concrete sign of attention and representation, not a complete translation of the intelligence that produced it.

This gradual disclosure also gives the scene its tension. The correct answers inspire wonder, but they do not end the argument over what counts as intelligence. Johanson’s challenge keeps the evidence from collapsing into an easy equation between successful computation and human-like understanding; the image, in turn, answers that challenge with a message tied to the real environment. The Yrr have arranged symbols, but those symbols depict the researchers’ actual ship against the surface waves. The exchange therefore marks a decisive advance in first contact while preserving its central uncertainty: humans can recognize that they have been answered, and can see themselves represented, yet still do not know how much of the Yrr’s world their interpretation can reach.