Source: https://guthlabs.ai/docs/instruments/light-travel-time/

instrument / verified-clean

# Light Travel Time

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Inspectable records

[01**Overview**Purpose and lifecycle](<https://guthlabs.ai/docs/instruments/light-travel-time/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/light-travel-time/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/light-travel-time/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/light-travel-time/qualification/>)

## Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

**Area**: Earth & Space (astronomy, orbital mechanics, meteorology, geology, geodesy, oceanography)

**Tranche**: tranche-4

**Evidence ID**: t4-077

**Ledger rows**: 1

No ledger note is attached.

## Review findings

Formula is valid for vacuum propagation over a specified path length, but the blank honest_label and missing physical/unit constraints require review. A more honest label is "Vacuum Light-Travel Time" with explicit supported units, exact conversion constants, Julian-year definition, and a warning that cosmological distance measures are not interchangeable with light-travel distance.

### Formula and scope findings

- t = d/c is the standard formula for propagation time through vacuum when d is a path length and d and c use compatible units.

- The input description "distance (any astronomical unit)" is ambiguous: it does not specify the accepted unit set, whether "astronomical unit" means AU specifically or any astronomical distance unit, or how units are selected and converted.

- The formula assumes a static Euclidean distance and vacuum light speed; it is not generally the cosmological light-travel time for comoving, luminosity, or angular-diameter distances.

- The specification does not define the year convention for output; Julian year (365.25 days) should be explicitly required.

### Unit assumptions

- c is the exact vacuum speed of light, 299792458 m/s.

- Distance and c must be converted to compatible units before division.

- 1 AU = 149597870700 m exactly.

- 1 light-year is defined using the Julian year: 1 ly = c × 31557600 s.

- Output years use 1 Julian year = 31557600 s.

- The distance is a nonnegative path length in vacuum.

## Boundary hardening

**BREAK_CLAIMED** · SELF_FLAGGED

The specification does not define behavior for negative distances, creating a convention-dependent result: signed arithmetic returns a negative travel time, while physical distance semantics require rejection or magnitude normalization. The extreme finite input also exposes floating-point precision limits, although it does not overflow.

## Errata and corrections

No applied erratum is attached to this unique-name record.

## Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

````
{
  "inputs": {
    "distance": 299792458,
    "distance_unit": "m",
    "c": 299792458,
    "c_unit": "m/s"
  },
  "expected_outputs": {
    "time_s": 1,
    "time_min": 0.0166666666666667
  },
  "working": "t = d/c = 299792458 m ÷ 299792458 m/s = 1 s. Convert to minutes: 1 s ÷ 60 = 0.0166666666666667 min."
}
````

## Related workflows

No source-defined multi-instrument workflow membership is recorded.

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`

- `evidence-tranche4/tranche4-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`