Constant lookup
Look up a physical constant by its key (e.g. "speed-of-light"), symbol (e.g. "c") or exact name. Returns the CODATA 2018 recommended value, unit, relative standard uncertainty (0 for values that are exact by SI definition) and category.
Go to this service →Our latest check (2026-10-11)
- Answering
- Yes — valid x402 payment terms
- Time to answer
- 397 ms
- Price
- $0.004 per call
- Paying buyers, last 30 days
- 1 (directory's own records)
- Paid calls, last 30 days
- 1
- Category
- Calculators and conversions
- Address
- https://physics.openverbs.com/v1/constant
Accuracy
Accuracy scores are published once a seller has enough paid checks against an independent record (at least 7 scored answers over at least 7 days). Until then no score is shown, and a missing score is never a pass.
For agents
This page as JSON: /sellers/6c15dc8c0fe1.json. Paid lookup by address: GET /api/seller?resource=… ($0.001, x402).