Relativistic light Doppler / redshift
API · /doppler-api
Doppler Effect API
healthy
4,014 Subscribers
Doppler-effect maths as an API, computed locally and deterministically. The sound endpoint computes the acoustic Doppler shift, f' = f·(v + vo) / (v − vs), where v is the speed of sound (given directly, derived from an air temperature, or the default 343 m/s at 20 °C), vs is the source velocity and vo the observer velocity, with positive velocities meaning approaching: it returns the observed frequency and the frequency shift, and refuses a supersonic source. The light endpoint computes the relativistic Doppler effect for light, f' = f·√((1+β)/(1−β)), from a velocity in metres per second or as a fraction of the speed of light and a direction (approaching blue-shifts, receding red-shifts), returning the frequency and wavelength factor, the observed frequency or wavelength, and the redshift z. The radial-velocity endpoint reverses it: from a measured redshift, or an observed and rest wavelength, it recovers the radial velocity with the exact relativistic relation and the simple v ≈ z·c estimate. Frequencies are in hertz, wavelengths in nanometres, velocities in metres per second. Everything is computed locally and deterministically, so it is instant and private. Ideal for physics and astronomy education, radar, sonar and lidar tools, audio and acoustics apps, and spectroscopy and redshift calculators. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is the Doppler effect; for sound levels and decibels use an acoustics API.
api.oanor.com/doppler-api
API health
healthy- Uptime
- 100.00%
- Server probes · 24h
- Avg latency
- 75 ms
- Server probes · 24h
- Subscribers
- 4,014
- active
- Total calls
- 80
- last 7 days
Pricing
Pick a tier — billed monthly, cancel anytime.
Free
Free
- 2,000 calls / month
- 2 requests / second
- Hard cap (429 above quota, no overage)
- Acoustic Doppler shift f' = f(v+vo)/(v-vs)
- Relativistic light/redshift endpoint
- Deterministic instant results
- JSON response with intermediate terms
Starter
€5.00 /month
- 25,000 calls / month
- 5 requests / second
- Hard cap (429 above quota, no overage)
- All sound + light Doppler endpoints
- Configurable medium sound speed
- Wavelength and redshift z output
- Email support
Pro
€15.00 /month
- 150,000 calls / month
- 15 requests / second
- Hard cap (429 above quota, no overage)
- High-throughput classroom/app volume
- Batch source-observer scenarios
- SI + imperial unit handling
- Priority support
Mega
€49.00 /month
- 786,000 calls / month
- 40 requests / second
- Hard cap (429 above quota, no overage)
- Bulk simulation-grade throughput
- Full relativistic + acoustic coverage
- Lowest per-call cost for EdTech platforms
- Priority support + SLA
Built by
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api.oanor.com/isotopes-api
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api.oanor.com/hotairballoon-api
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api.oanor.com/vacuum-api
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Centre-of-mass and barycentre mechanics as an API, computed locally and deterministically. The point-masses endpoint computes the centre of mass of a system of point masses in one, two or three dimensions, applying x_com = Σ(m_i·x_i)/Σm_i to each axis from a list of masses and their x (and optional y and z) coordinates — masses of 1, 2 and 3 at positions 0, 1 and 2 give a centre of mass at 1.333, and four equal masses at the corners of a square sit at its centre. The two-body endpoint computes the barycentre of two masses separated by a distance, r1 = d·m2/(m1+m2) from the first body, which always lies closer to the heavier one — for the Earth-Moon system the barycentre is about 4 670 km from Earth’s centre, still inside the planet. Lists may be passed as comma-separated values (masses=1,2,3&x=0,1,2) or as JSON arrays in a POST body, and units are consistent and unit-agnostic. Everything is computed locally and deterministically, so it is instant and private. Ideal for physics, engineering-statics, astronomy, robotics, game-physics and mechanics-education app developers, balance-point and barycentre tools, and simulation software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 2 endpoints. This is the centre of mass; for the rotational moment of inertia use a moment-of-inertia API.
api.oanor.com/centerofmass-api
Frequently asked questions
Quick answers about pricing, quotas, and integration.
How do I get an API key for Doppler Effect API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Doppler Effect API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Doppler Effect API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Doppler Effect API cost?
Doppler Effect API has a free tier with 100 calls / month. Paid plans start at €5.00 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Doppler Effect API GDPR-compliant?
All requests to Doppler Effect API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.
Pick an endpoint from the list on the left to see its details and try it.
Code snippets
Sign up to get an API key, then call any path under your slug.
curl https://api.oanor.com/doppler-api/SOME_PATH \
-H "x-oanor-key: oanor_test_..."const res = await fetch("https://api.oanor.com/doppler-api/SOME_PATH", {
headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();$ch = curl_init("https://api.oanor.com/doppler-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);import requests
r = requests.get(
"https://api.oanor.com/doppler-api/SOME_PATH",
headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())Ratings
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