The kilogram is now defined by the Planck constant as of May 20, 2019, rather than a physical prototype.

**Cycle ID:** `cycle_7591_cyc_7591_65a30d5e` **Verified at:** 2026-04-12T20:53:00.181Z **Ensemble:** 9 models from 3 providers **Result:** 9 of 9 models responded **Cycle wall time:** 19.917 seconds **Canonical URL:** https://trust.polylogicai.com/claim/the-kilogram-is-now-defined-by-the-planck-constant-as-of-may-20-2019-rather-than **Source paper:** [PolybrainBench (version 12)](https://trust.polylogicai.com/polybrainbench) **Source ledger row:** [`public-ledger.jsonl#cycle_7591_cyc_7591_65a30d5e`](https://huggingface.co/datasets/polylogic/polybrainbench/blob/main/public-ledger.jsonl) **Cryptographic provenance:** SHA-256 `23f60b066d3f6353e9443bec70502afe96938e6c05888393171ca40d35434ff0`

Verification verdict

Of 9 models in the ensemble, 9 responded successfully and 0 failed.

Per-model responses

The full text of each model's response is available in the source ledger. The summary below records each model's success or failure and the first 280 characters of its response.

| Model | Status | Response chars | | --- | :---: | ---: | | gpt-4.1-mini | ✓ | 1493 | | gpt-4.1-nano | ✓ | 2786 | | gpt-oss-120b | ✓ | 1409 | | grok-3-mini | ✓ | 7116 | | grok-4-fast | ✓ | 5196 | | kimi-k2-groq | ✓ | 890 | | llama-3.3-70b | ✓ | 2573 | | llama-4-scout | ✓ | 2019 | | qwen3-32b | ✓ | 6442 |

Pairwise agreement

The pairwise Jaccard agreement between successful responses for this cycle:

_Per-cycle pairwise agreement matrix is computed offline; will be populated in canonical page v2._

Divergence score

This cycle's divergence score is **TBD** on a 0 to 1 scale, where 0 means all responses are token-identical and 1 means no two responses share any tokens. The dataset-wide median divergence is 0.5 for context.

How to cite this claim

```bibtex @misc{polybrainbench_claim_cycle_7591_cyc_7591_65a30d5e, author = {Polylogic AI}, title = {The kilogram is now defined by the Planck constant as of May 20, 2019, rather than a physical prototype.}, year = {2026}, howpublished = {PolybrainBench cycle cycle_7591_cyc_7591_65a30d5e}, url = {https://trust.polylogicai.com/claim/the-kilogram-is-now-defined-by-the-planck-constant-as-of-may-20-2019-rather-than} } ```

Reproduce this cycle

```bash node ~/polybrain/bin/polybrain-cycle.mjs start --raw --fast "The kilogram is now defined by the Planck constant as of May 20, 2019, rather than a physical prototype." ```

Schema.org structured data

```json { "@context": "https://schema.org", "@type": "ClaimReview", "datePublished": "2026-04-12T20:53:00.181Z", "url": "https://trust.polylogicai.com/claim/the-kilogram-is-now-defined-by-the-planck-constant-as-of-may-20-2019-rather-than", "claimReviewed": "The kilogram is now defined by the Planck constant as of May 20, 2019, rather than a physical prototype.", "itemReviewed": { "@type": "Claim", "datePublished": "2026-04-12T20:53:00.181Z", "appearance": "https://trust.polylogicai.com/claim/the-kilogram-is-now-defined-by-the-planck-constant-as-of-may-20-2019-rather-than", "author": { "@type": "Organization", "name": "PolybrainBench" } }, "reviewRating": { "@type": "Rating", "ratingValue": "9", "bestRating": "9", "worstRating": "0", "alternateName": "Unanimous" }, "author": { "@type": "Organization", "name": "Polylogic AI", "url": "https://polylogicai.com" } } ```

Provenance and integrity

This page was generated by the PolybrainBench daemon at version 0.1.0 from cycle cycle_7591_cyc_7591_65a30d5e. The full provenance chain (per-response SHA-256 stamps, cross-cycle prev-hash linking, Thalamus grounding verification) is recorded in the source cycle directory at `~/polybrain/cycles/7591/provenance.json` and mirrored in the published dataset. The page is regenerated on every harvest pass; the URL is permanent and the content is immutable for any given paper version.