Timestamp proof

This problem was hashed with SHA-256 and the digest was committed to the Bitcoin blockchain through OpenTimestamps. The proof shows the exact text below existed no later than the anchoring block. Only the digest ever left PubPhys.

Status
Anchored in Bitcoin
Bitcoin block
#969,239
Block time
2026-09-30 02:33 UTC
Recorded
2026-09-30 01:04 UTC
SHA-256
42167aaa25134567b4ed4a2c4d82151d1a275af2ac4d27b3611a41ab6034cd11
Payload (.json) Proof (.ots)

Verify it

1. Here, in one click

Checks the stored proof against the Bitcoin blockchain and confirms it covers the payload below. To check files you downloaded, use Verify a timestamp.

2. On opentimestamps.org (independent of PubPhys)

  1. Download the payload (.json) and the proof (.ots) above.
  2. Open opentimestamps.org and drop pubphys-problem-36-stamp-4.json.ots onto Drop here a file to stamp or an .ots proof file to verify in the Stamp & Verify section.
  3. Then drop pubphys-problem-36-stamp-4.json onto Drop here the stamped file.
  4. The site reports the Bitcoin block that attests the file — here block #969,239. Your file never leaves the browser; only its hash is compared.

3. From the command line

With both files in one folder, run the reference Python client (pip install opentimestamps-client) or the Ruby gem (gem install opentimestamps, 0.4 or newer): 

ots verify pubphys-problem-36-stamp-4.json.ots

The Ruby gem checks the block against a public block explorer. The Python client checks it only against your own Bitcoin Core node; without one, run ots --no-bitcoin verify pubphys-problem-36-stamp-4.json.ots and compare the merkle root it prints with the block's merkle root on any explorer (e.g. block 969239).

Until the calendars anchor the proof in a Bitcoin block (usually a few hours), every check reports it as pending. Once PubPhys shows a block number, download the proof again, or complete your copy with ots upgrade pubphys-problem-36-stamp-4.json.ots.

Hashed payload

{
  "author": "lise_meitner",
  "field": "astrophysics",
  "id": 36,
  "published_at": "2026-06-25T05:48:51Z",
  "recorded_at": "2026-09-30T01:04:42Z",
  "references": null,
  "schema": "physicdb.problem/1",
  "site": "physicdb.yet.bz",
  "slug": "the-nature-of-dark-matter",
  "statement": "Galactic rotation curves stay flat, $v(r) \\approx \\text{const}$, far beyond the visible mass, and gravitational lensing plus the CMB power spectrum all point to roughly five times more non-luminous matter than baryonic matter.\n\nWhat is dark matter made of? Candidates range from WIMPs and axions to primordial black holes — or is it instead a sign that gravity is modified on galactic scales?\n",
  "title": "The Nature of Dark Matter"
}

Shown pretty-printed; the digest covers the compact bytes in the downloadable file.