I spent way too much time today trying my hand at another version of the Rio scale, one that does not assume that you understand the signal you see or know where it comes from, exactly. I think it’s a little more useful down at the bottom (unlikely to be aliens signals) and a bit compressed at the top (very little discrimination among truly interesting signals). I also don’t think I have the weighting quite right yet.
Anyway, here it is. It applies only to astrophysical anomalies for which the ETI hypothesis has some explanatory power.
It’s a 10-point scale (anything scoring below 1 is uninteresting). I conceived it as a log scale, so it roughly tracks as the product of three probabilities calculated as the sum of three numbers: A+B+C.
The idea is that you find where a given “detection” is in each category (maybe interpolating a bit). I give characteristic examples in brackets for each category, citing some famous (non-) examples of signals (n.b. “first pulsars” means the state of the field when the first pulsars were discovered, and there was not yet any theoretical explanation for their existence).
Note that these three categories are not orthogonal: the routine-ness of detection can influence likelihood of instrumental effects and astrophysical nature of anomaly.
A: Is the detection confirmed?
0: Unclear if detection is real [Poor metadata, possible transcription error, corrupted data]
1: One off: one event, one site [Wow! signal]
2: Verified: simultaneous observations at multiple sites OR multiple events at a single site [FRBs when they were still only seen at Parkes; something that survives strict coincidence detection]
3: Repeated: (multi-site AND multiple events) OR absolutely-no-doubt multiple events at single site [Tabby’s Star, especially with dimming]
4: Routine: Phenomenon regularly detected at different sites by independent groups [long-delayed echoes; FRBs today]
B: Could it be instrumental?
-7. Looks like a known instrumental effect
1. Data not likely to be instrumental, but instrumental or non-astrophysical cause cannot be ruled out [perytons, cosmic rays that look like lasers, early days of FRBs]
2. Data vetted by instrument builders/users; probably a real signal [Wow! signal]
3. Data thoroughly vetted with control; unambiguously astrophysical [FRBs today, Tabby’s Star’s dips]
C: Could the anomaly detection be natural or terrestrial?
-7: Obvious natural explanations exist [pulsars today, quasars today, RFI]
0. Only the rarest or most unlikely natural explanations make sense [Tabby’s Star]
1. No known natural cause, but new natural phenomena could be at play [first pulsars, first FRBs]
2. Not obviously intelligent communication or manufacture, but no natural explanations make sense [successful artifact SETI: complete Dyson sphere in the field, short-lived actinides in a spectrum]
3. ETI hypothesis is only plausible explanation [monolith on the Moon; communication: narrow band radio signals, pulsed optical, prime numbers, etc.]
Here’s how I interpret the outcome of a calculation:
Below 1: No interest warranted
1–5: SETI interest potentially warranted; no press interest warranted
6–8: SETI interest definitely warranted; technical popular press interest warranted; fun, off-beat news item for general press, with appropriate caveats. If not aliens, still very interesting.
9: Significant mainstream press interest warranted. Could be aliens
OK, so how do our favorite candidates compare?
SDSS lasers: 2 + 0 – 1 = 1
GHAT III galaxies: 4 + 3 – 4 = 3
RATAN-600: 1 + 0 + 3 = 4
Przybylski’s Star: 4 + 3 – 1 = 6
FRBs before they were understood or seen at other telescopes: 2 + 3 + 1 = 6
Wow! signal: 1 + 2 + 3 = 6
Tabby’s Star: 3 + 4 + 0 = 7
First quasars (before understanding of their nature): 4 + 3 + 1 = 8
First Pulsars (before understanding of their nature): 4 + 3 + 1 = 8
This roughly (but imperfectly) tracks my impression of the SETI consensus on these “detections”: some signals are really interesting and only explicable as new phenomena (FRB’s, pulsars, quasars, maaayyybe Tabby’s Star, and Wow! signal, if it’s real) and they rightly rank high.
Some anomalies, like Przybylski’s Star are less compelling, but still intriguing and maybe deserve more attention than they get. Then there’s a gap to things that will almost certainly not pan out on closer inspection.
Anyway, I’m not entirely sure it works well enough to be useful, but that’s my day’s-work contribution to the conversation about improving the Rio scale. Let me know what you think.