SEND A SIGNAL. WAIT FOR THE REPLY.
The Last Transmission / DarkScienceDocs.com
Teaching method 1.0 / resource release 268 / October 25, 2026
https://darksciencedocs.com/scale-lab/#teaching

START HERE
Four-page US Letter packet: learner pages 1-2, educator pages 3-4.
Choose Fit for A4. Ages 12+; about 30-40 minutes with calculator.
Use paper or the existing Spacecraft signal delay tool. Choose Mars for
worked case 3; near-side alignment starts automatically. Change alignment
for case 4. Changing Distance unit converts the same physical separation.
No account, submitted answers or student information required.

RUN OFFLINE
Extract the complete folder. Python 3.9+ needs only its standard library:
  python3 verify_analysis.py --data-dir .
Windows:
  py -3 verify_analysis.py --data-dir .
Compare emitted JSON with worked-result.json. The checker makes no network
request and changes no inputs. It validates eight pinned reference rows,
five generated cases, circle geometry, one-way/reply times and four unit
representations. It checks stored transcriptions and arithmetic, not live
positions, mission telemetry or scientific interpretation.

FILES
reference-inputs.csv: eight definitions/conversions/rounded references,
with status and primary-source URLs. Mars element 1.52371034 AU rounds to
1.524 AU in the lab; Earth's 1 AU circle is a chosen teaching radius.
generated-signal-cases.csv: five GENERATED static comparisons; not measured
travel times or actual minimum/maximum Mars ranges.
worked-result.json: separate Python calculations, unit checks and hashes.
verify_analysis.py: Python standard-library checker.
scale-lab-model.js and black-holes-guide-model.js: unchanged original model
and its helper dependency. package.json declares ES modules for optional
Node import inspection. Python does not need Node or these JS sources.

RECIPE / INPUT STATUS
Vacuum c = exactly 299792.458 km/s (SI definition).
1 AU = exactly 149597870.7 km; international mile = exactly 1.609344 km.
Julian year = 365.25 days = 31557600 s; light-year = c times Julian year.
Case 1 Moon = rounded mean center-to-center distance 384400 km, not a fixed
surface-station range. Case 2 Earth-L2 = rounded 1500000 km region reference
for Roman orbital design, not a live telescope range or distance from Sun.
Cases 3/4 adopt coplanar circles of radii Earth 1 AU, Mars 1.524 AU:
 near = abs(1.524-1)*AU; opposite = (1.524+1)*AU.
At exact opposite-side alignment the SUN BLOCKS a direct path. Case 4 is a
geometric comparison, not an available direct link. These are not actual
closest/farthest separations; real orbits are elliptical and inclined.
Case 5 Proxima = rounded 4.24 light-years with hypothetical receiver.
No inhabitants, detectable signal or current receiver is claimed.
For each static separation d: one way = d/c; immediate reply = 2*d/c.
Unit conversions preserve physical distance, so they preserve delay.

WORKED CASE 3
Distance = 0.524 AU = 78389284.2468 km = about 48708843.011065 miles.
One way = 261.478506730146 s = 4 min 21.478507 s.
Immediate reply = 522.957013460292 s = 8 min 42.957013 s.
If receiver waits 30 s: 2*d/c+30 = 552.957013460292 s = 9 min 12.957013 s.
Bandwidth changes information throughput, not vacuum propagation speed.
Case 1: 1.282220381942 s one way, 2.564440763883 s reply.
Case 2: 5.003461427972 s one way, 10.006922855945 s reply.
Case 4: 1259.488074402459 s one way, 2518.976148804918 s doubled path.
Case 5: 4.24 Julian years one way, 8.48 years immediate hypothetical reply.

LIMITS
Straight vacuum propagation and constant separation, instantaneous reply.
No motion during exchange, plasma, relativistic corrections, transmission
duration, processing or mission scheduling. Rounded distances remain
approximate even though unit conversions are exact. Stored digits support
repeatable arithmetic, not observational precision. No independent
scientific review or formal curriculum alignment is claimed.

PRIMARY SOURCES / CHECKED OCTOBER 25, 2026
BIPM SI metre / c: https://www.bipm.org/en/si-base-units/metre
AU definition: https://syrte.obspm.fr/IAU_resolutions/Sumredef_au.html
Mile: https://www.nist.gov/pml/us-surveyfoot/revised-unit-conversion-factors
Julian year: https://ssd.jpl.nasa.gov/astro_par.html
Moon: https://science.nasa.gov/moon/facts/
Roman L2 design: https://ntrs.nasa.gov/citations/20210018417
Mars J2000 element: https://ssd.jpl.nasa.gov/planets/approx_pos.html
Proxima: https://science.nasa.gov/sun/facts/
Telecom: https://science.nasa.gov/learn/basics-of-space-flight/chapter10-1/

CREDIT AND SHARE
Original activity, diagram, cases and checker by The Last Transmission.
Print/share complete packet with attribution and source trail. Cite
Scale Lab: Send a Signal. Wait for the Reply, DarkScienceDocs.com,
method 1.0 / resource 268, October 25, 2026; add access date.
Not a NASA, JPL, BIPM, IAU or NIST product or endorsement.
Corrections: https://darksciencedocs.com/contact/ (Scientific correction).
Include setting, result and evidence.

FILE INTEGRITY / SHA-256
send-a-signal-teaching-packet.pdf: 6a4a0d3285d8f96c546c52b75a52d4e730de231b78ae4df23f4084120889f2fb
verify_analysis.py: e70931dbb4da47232b4cfa84300bb9350e6cfe66851a4512c3460776a3a26377
worked-result.json: 648337d36dcdfd169e8ec0f39cb72611f4d0979b4fd9f2aa6d3bd4bb7e04df26
reference-inputs.csv: 6858bc9522ff1471bfe4f8c2e3345e50dd9c4a2af47e81ca49016cb008f8842a
generated-signal-cases.csv: 38fc2154039a41e9128ba58053c6ec6eaa7ba4f85891ebbef83f65d824b9dc0c
scale-lab-model.js: 0dd04e5f3c517da03c42982b3175d05ffbf7b8e80af538b128840ba7667f0cc2
black-holes-guide-model.js: 07b1fbcc0183344025242dcc4dca94c57e8c60e697e2d8422b0652c417730577
