Newton

Newton predicts where a thrown ball will land from only the first quarter second of an ordinary video, before the ball gets there, then answers spoken what-if questions by replaying the same throw under new physics. You upload a side-on clip and click the ball and the floor. Newton tracks the ball, freezes the video 0.25 s after release, draws the predicted arc and a target ring, then resumes playback so you see the real ball land and the error in centimetres. On a real 30 fps hand toss it was 0.7 cm off, from 8 frames. The problem: physics is usually taught with idealised numbers, and measuring a real experiment needs special equipment and calibration. Newton turns any phone video into a measured experiment. It uses the ball's own size as the ruler, fits the physics, and proves the fit by predicting the future. The code enforces that the models never see frames after the freeze, so the prediction is honest.