AI can fake pixels. It can't fake physics.

Send a video of something falling, thrown or bouncing. Pisa measures its motion and tells you whether real gravity could have produced it.

Check a videoHow it works
Real gravityThe video
Gravity in the video2.0 m/s²
On Earth9.81 m/s²
Physically impossible4.9 times weaker than on Earth
Illustration: a ball dropped from 1.5 m, photographed 15 times a second. Dashed lines join the two balls at the same instant.
  • The ghost: where real gravity puts the ball
  • The ball as it falls in the video
  • The same instant for both

An answer with evidence, not an opinion

On the web and on WhatsApp, Pisa replies with three things anyone can check.

Pisa
ForwardedIs this real?
Physically impossibleTwo objects released together fall at different rates. Under real gravity they fall side by side, as Galileo showed.In the video, each lime circle shows where the object would be if both fell together.Measurements and evidence: pisa-theta.vercel.app

  1. The ghost

    The lime circle shows where real gravity would put the object.

  2. The verdict

    One of three answers, in plain words.

  3. The numbers

    What Pisa measured, so anyone can check it.

  4. Your language

    English, Spanish, Chinese and Portuguese.

Pisa's real reply to a computer-made test clip: two balls dropped together, one under Earth's gravity and one under gravity about 4 times weaker.

How Pisa checks a video

  1. Muse Spark

    Watching

    Pisa finds the moment something falls, is thrown or bounces, and checks the camera is steady enough to measure.

  2. SAM 3.1

    Tracking

    Meta's SAM 3.1 outlines the object in every frame, so its path is measured, not guessed.

  3. Pisa's physics engine

    Measuring

    The path is tested against the laws of free fall. Air can slow a fall; nothing real slows down in mid-air.

  4. Muse Spark

    Explaining

    You get one of three answers, the numbers behind it, and the ghost to see it for yourself.

Why measure instead of asking a chatbot

Closer to the Moon than to Earth.

The gravity objects fall with in videos from today's generators. On Earth it is 9.81. Source: arXiv 2512.02016

0%

Clean, real throws and bounces that a vision model tuned for physics accepted as plausible. Measuring the motion scored them 0.96 to 0.99. Source: Morpheus, ICML 2026

How we know Pisa works

Three possible answers

What Pisa checks

Checks

  • Falls
  • Throws
  • Bounces
  • Two objects dropped together

Doesn't check

  • Face swaps
  • Lip-sync
  • Cloned voices

Got a video that doesn't add up?

Check it in under a minute. No account, and Pisa keeps only the measurements.

Check a video