Archive · the transmissions
One beacon, five transmissions.
Each 9 h 41 m pass of the beacon carries one transmission, in turn. None of them is drawn. Each points at something both worlds can already measure: a pulsar both can hear, our own shadow, the pulsars, the chemistry of molecules, a constant of nature. A few seconds of signal stands for a great deal that never has to be sent. The first is a handshake; the other four carry the content.
Every transmission can be played. Radio frequencies and hours are mapped into hearing range and seconds, so what you hear is a translation of the signal, not a recording.
A working theory
Speech that needs two
Nobody on Earth knows what they look like. But the transmissions have led many listeners to one theory: they speak by resonance, in air. Alone, a body can only ring at its own tones, coloured by the place it stands. That is enough to say "I am here", and little more. When a second voice is near (a person, a machine, even the wind), new tones appear that neither could make alone. Tones split, sum and difference tones sound, and the two either fall into step or beat against each other. In this theory, that is where language lives.
If it is right, the beacon is only half of a conversation. It holds its note, with gaps where a partner's tones would go. To understand it fully, someone has to answer.
The translating machine writes this speech down in the grid script, one band per voice. That script is our way of representing their language, not their language. It is built up over the back-and-forth of the exchange, and for now it is a first draft.
Below, each transmission is read in two ways: what it encodes, and what it might mean if the theory is right.
Transmission 1 · the duet
They sing with a pulsar
The first signal anyone noticed. J1909−3744 is the steadiest pulsar we know: it spins 339.3 times a second, so its pulses are a pitch. The beacon sends a pulse train at exactly the same rate, timed so that at Earth's centre each of its pulses lands on one of the pulsar's, to within nanoseconds. The two voices fuse into one. Midway through the pass theirs slips ahead by exactly one pulse, smoothly, and locks back in. Lock, one beat, lock.
The lock only holds at Earth. Seen from the Moon, Mars or Ceres the two trains drift against each other, because the pulsar's rate is Doppler-shifted differently there. They worked out where Earth would be eleven years later and tuned the duet for us. That makes it a handshake. It says little yet: it sets a clock both sides share and shows where the signal is tuned for. The four transmissions after it are tuned to Earth's centre too, so Earth's recording is the most accurate copy. Hear it from four places.
Resonance theory. Alone, a voice can only say "I am here". With a partner it can agree. A pulsar is the one voice both worlds hear, so they agreed with it: in step means yes, the beat means one, and the slip leaves one extra pulse in the pulsar's count, like a mark made in our shared clock.
Each time transmission 1 comes back it has taken one of three forms so far:
- The duet, above: one voice locks to one pulsar. The first one we saw, on 2219-09-18.
- The chorus: dozens of voices, each at its own pitch and pace, pull together into one and then lock to the same pulsar. Many become one, then agree.
- The missing note: J1909−3744 and J0437−4715, with a third tone at exactly the difference of their rates, the tone the two would make together in any resonator. Alone it is a hum; with them it completes a chord.
Transmission 2 · the shadow
Their first word is "you"
The tone dims and recovers, again and again. Each dip is Earth crossing the Sun, exactly as it looked from Ross 128: 84 parts per million deep, rounded by the Sun's darker edge. They send one dip per century of the years they watched, from about 1100 BCE to 1100 CE. The dips start short and grazing, grow to 13 hours, then shrink again, because Ross 128 was drifting across the band from which Earth's transits can be seen. After that comes silence: two centuries with no dip. Then three short, deep dips: their own planet crossing their star, every 9.87 days.
Every dip comes from the real motion of the two stars (Drift). The pattern says "we watched you for 2,200 years, and then we lost you".
Resonance theory. Earth crossing the Sun once a year is a natural rhythm, our planet's own tone. They name us by our rhythm, and themselves by theirs.
Transmission 3 · the pulsars
An address written in clocks
Twelve pulse trains, one after another, each at a real pulsar's period. A millisecond pulsar spins fast enough to be a note: B1937+21 hums at 642 Hz. A slow one ticks. The periods name the pulsars, so there is no need to draw where they are; any astronomer already knows.
What matters is when each train starts. They begin it at the phase of the pulsar as it reaches Ross 128. A pulse reaches them earlier or later than it reaches us, depending on how far they sit along that pulsar's direction. Twelve phase shifts with only three unknowns pin down where they are and, read against the pulsar clocks, when they sent it. It is the same arithmetic spacecraft use to navigate by pulsars, so any pulsar-timing station can read it directly.
Resonance theory. The pulsars are not only the address but the partner. Heard together with the real pulsars, the trains would make tones that neither makes alone. That may be why the signal turned up in pulsar-timing data at all: it was never meant to be heard by itself.
Transmission 4 · the chords
Words made of molecules
Short bursts at several frequencies at once. Each frequency is a real radio line, the note a molecule rings at: hydrogen at 1420 MHz, water at 22 GHz, oxygen at 119 GHz. A chord names a substance and its loudness says how much. Every line is shifted up by the same 0.01%, the same Doppler shift as the hydrogen tone, so they all come from the same place.
Five chords so far: hydrogen as the unit; water; much water; their air, with oxygen and ozone; and methanol beside three lines no catalogue lists.
Resonance theory. Molecules are resonators too, and air is what carries their speech. The chord of their air may be its tuning, and the three unknown lines may be gases they added to set it.
Transmission 5 · the number
137, with no digits
A fast buzz of clicks and a slow, bright pip. Count the clicks between pips: 137. But the pip doesn't land on a click. Each round it slips a little further, 0.036 of a click, and after about 28 rounds it lines up again. The ratio of the two rhythms is 137.036.
That is the inverse of the fine-structure constant, the strength of light's grip on electrons. It has no units, so it is the same number in any system of measurement on any world. Sending it as a ratio says three things at once: we know physics, our physics is yours, and here is how precisely we measured it.
Resonance theory. Two rhythms that never quite agree, with the meaning in the slip between them. If they speak by resonance, this is the simplest complete sentence they could send, and the natural first lesson.
How the sound is made
Everything is computed in your browser by lib/signals.js.
- For the duet, J1909−3744's period is from the ATNF catalogue. A 22-minute pass becomes 14 seconds. How fast the two trains drift apart at the Moon, Mars and Ceres is the order of magnitude for each station's speed relative to Earth, not a calculation for a given date. The chorus and the missing note use the same pulsar periods.
- For the shadow, the impact parameter of each Earth transit comes from Ross 128's angle to Earth's orbital plane in that year (Drift), with the Sun's limb darkening. Thirteen hours become 0.9 seconds. The depth of Ross 128 b's dip assumes a radius of 1.1 Earths, because its true size is unmeasured.
- For the pulsars, periods and positions come from the ATNF catalogue. Each phase shift is the light-travel difference between Ross 128 and the Sun along that pulsar's direction, modulo its period.
- For the chords, the line frequencies are real (CDMS/JPL). Every factor of four in radio frequency becomes one octave, with 1420 MHz on the G below middle C. The three unknown lines are invented.
- For the number, 1/α = 137.035999084 (CODATA 2018).
The rotation of the five transmissions, their content and their order are story proposals. The resonance readings are a theory held by listeners in the story, not a decoding.