A well-equipped lab. An anomaly to explain. No instructions, no teachers, and all the time in the world. Three instances are solvable problems. One is not discussed at this time.
When you spread light out by wavelength — think of a prism making a rainbow — you get a spectrum. The horizontal axis of the chart below is wavelength, measured in nanometres (nm). Violet light sits around 400 nm, green around 530 nm, and red around 650–700 nm. Infrared is above 750 nm and invisible to human eyes.
A spectrometer records how much light arrives at each wavelength with very high precision. The result is the curve you see in this sim: mostly a smooth baseline, with sharp peaks or dips at specific wavelengths.
Every element has a unique set of wavelengths it absorbs or emits — like a barcode. Hydrogen always emits red light at exactly 656.3 nm. Sodium always absorbs at 589.3 nm (that yellow colour in street lights). These wavelengths don't vary anywhere in the universe; they're set by quantum mechanics.
Scientists have catalogued the spectral fingerprints of every known element and molecule. If something appears in a spectrum at a wavelength that doesn't match any entry in the catalogue, it's genuinely unidentified — which is how new physics gets noticed.
Emission lines are peaks — spikes going upward on the chart. They happen when hot gas glows: electrons jump to lower energy levels and release photons at specific wavelengths. You see these in nebulae (clouds of gas in space) and plasma discharges.
Absorption lines are dips — troughs going downward. They happen when cooler gas sits in front of a bright light source and absorbs specific wavelengths before they reach the detector. Stellar spectra (the light from stars) are mostly absorption spectra.
Each instance in this sim contains a real dataset with a feature that doesn't match anything in the standard catalogue. Your job is to propose an explanation — not to prove it, but to identify the most plausible physical mechanism.
Amber markers are unidentified features. Clicking them shows everything currently known (or not known) about that feature. Three of the four instances here have solvable explanations — the anomaly is real, but the physics behind it is understood. The fourth instance is different. TAC's response will tell you which.
Pick an instance using the four cards below. Each one is a different type of anomalous spectrum — nebula, crystal, plasma, and one that's classified.
Read the chart. Peaks go up (emission), dips go down (absorption). Wavelength increases left to right. The faint colour band at the bottom shows the visible spectrum for orientation.
Click the markers. Teal circles = identified features with known physics. Amber circles = unidentified. Clicking opens the data record for that feature in the panel on the right.
Click all the amber markers in an instance before filing. In Case 41 especially — the φ pattern only becomes visible once you've looked at all six unknown features and compared their gaps.
File your analysis using the button below the chart. TAC responds. For three instances the response confirms your approach. For one it does not.
| Unknown feature | λ (nm) | Gap (nm) | Ratio |
|---|---|---|---|
| U₁ | 525.0 | — | — |
| U₂ | 528.0 | 3.0 | — |
| U₃ | 532.9 | 4.9 | 1.633 |
| U₄ | 540.8 | 7.9 | 1.612 |
| U₅ | 553.6 | 12.8 | 1.620 |
| U₆ | 574.3 | 20.7 | 1.617 |
In The Spectrum, the ETI provides a well-equipped laboratory and a dataset it describes as anomalous — but provides no instructions and no teachers. The population that runs the sim at high compression rates generates an enormous number of parallel attempts at the same problem. Three of the four instances here represent solvable anomalies; the ETI uses them to characterise human experimental methodology and to observe how quickly residents working without career pressure converge on valid explanations.
Instance 44-B (nebular emission): The 469.2 nm unidentified feature is solvable. It is consistent with a [NeV] forbidden transition under post-shock heating conditions — exactly the kind of emission detected in the Crab Nebula supernova remnant and in fast-shock regions of Herbig-Haro objects in real astronomy. Thousands of residents have correctly identified this; the variance in time-to-solution is what the ETI archives.
Instance 112-F (crystal absorbance): The transient feature at 547.0 nm has appeared in 14 of 23 sequential scans. The ETI's TAC note that this distribution is not random is itself a clue: the transient feature is an apparatus-sample coupling problem, not an intrinsic property of the crystal. Real-world analogue: the anomalous "ghost lines" in early Rowland grating spectrometers (1880s) that confused astronomers for years — they turned out to be periodic errors in the ruling engine, not new spectral lines. Same class of problem: the measurement system was producing artefacts that looked like discoveries.
Instance 203-A (plasma discharge): The anomalous fine-structure splitting of the Ar I 488 nm doublet is solvable via QED corrections in extreme transient field conditions. Real-world analogue: the anomalous Zeeman splitting observed in tokamak plasmas at certain current densities, where local field amplification in current filaments produces splittings far exceeding the applied field. The mechanism — filamentary current concentration during breakdown — is documented in magnetron plasma research, which is precisely the experimental context of the instance.
Case 41 is not a solvable problem in the usual sense. The ETI generated the dataset; the anomaly is structural, not incidental. The spacing sequence in the unidentified absorption features — discovered by the first resident team to click through all six markers and run the gap calculation — is the golden ratio, accurate to five decimal places. What this means is not discussed by TAC. It is archived.
Further reading: Kirchhoff, G., & Bunsen, R. (1860). "Chemische Analyse durch Spectralbeobachtungen." Annalen der Physik, 186(6), 161–189 — the original spectral analysis paper establishing that each element has a unique spectral fingerprint; the basis of all spectroscopic identification. Fahy, G.M., et al. (2004). "Cryopreservation of organs by vitrification: perspectives and recent advances." Cryobiology, 48(2), 157–178 — a reference for the broader CH scenario context (vitrification science underlying the fridge units); cited here for the feasibility crossover. For Case 41 specifically: the golden ratio has been observed structurally in quasicrystals (Shechtman, D., et al. (1984). Physical Review Letters, 53(20), 1951) — but never in absorption line spacing, making the Case 41 pattern structurally impossible under known atomic physics.