Your phone's hidden lab
Your phone carries an accelerometer and a gyroscope that most apps use quietly for screen rotation and step counts. Here you can see them live and use them for real experiments. Guess first, then measure. Open it on your phone.
How many floors did the lift go?
- Get in the lift and hold the phone still (or put it flat on the floor).
- Press Start while the doors are still open. Keep still for 2 seconds while it calibrates.
- Ride the lift. Press Stop when the doors open.
The lift only pushes you during the first and last two or three seconds of a ride. In between it moves at a steady speed and you feel nothing. Adding up the acceleration once gives speed, and adding up speed gives height. Small errors grow fast, so the page assumes the lift ends at rest and corrects for that.
Measure gravity with a pendulum
- Hang the phone from a charger cable or string, screen facing you. Put something soft below, please.
- Measure from the pivot point to the middle of the phone and type it in.
- Pull it a little to one side (small swings), let go, then press Start. It times 10 swings.
- Hang any small weight (keys work) from a string and measure its length to the weight's centre.
- Pull it a little to one side and let go.
- Tap the big button every time the weight passes its lowest point going right. Ten taps or more is good.
A pendulum's swing time depends only on its length and gravity: T = 2π√(L/g). So timing the swing measures g. In the UAE it's about 9.79 m/s², slightly less than at the poles (9.83) because the Earth bulges at the equator and spins. A phone is not a point weight, so expect to land within a few percent.
Spirit level and shelf check
A phone's camera bump can tilt it, so calibrate on a surface you trust. Or use the carpenter's trick, which the Measure button does for you: read the angle, turn the phone round 180° on the same spot, and read again. The real slope is half the difference between the two readings. On a 1 m shelf, 0.5° is about 9 mm from one end to the other.
Step counter
- Put the phone in a pocket or hold it in your hand.
- Press Start and walk normally for 30 seconds.
Every step sends a small jolt through your body when your heel lands. The counter smooths the signal and counts the jolts that are at least a third of a second apart. Stride length is roughly 41% of your height, a common rule of thumb.
How hard was that?
- Hold the phone tight and shake it, or tap it on your palm. You can also drop it onto a bed or cushion from a low height.
- Please don't drop it onto anything hard, and keep a firm grip when you shake.
While it's falling, the phone feels weightless, so its accelerometer reads close to zero. The page times that quiet moment and works out the drop height from h = ½gt². A hard landing on a tiled floor can reach several hundred g for a split second, but phones only take about 60 to 100 readings a second, so short spikes are under-read.
Live sensors Sample data
What's inside your phone
A tiny silicon comb on a spring. When the phone accelerates, the comb lags behind and the gap between its teeth changes, which changes a capacitance.
Lying still on a table, the phone reads 9.8 m/s² upward. That's the table pushing back against gravity. In free fall, it reads almost zero.
It uses a vibrating mass that gets nudged sideways when the phone turns. That's how it measures how fast the phone is rotating.
Websites must ask before reading motion on iPhone. Other browsers may allow it quietly, so a page could tell if you're walking or still. This page keeps every reading on your phone.
Sources: the W3C "DeviceOrientation Event" specification (how browsers share motion data and why iPhone asks permission); the International Gravity Formula used in the WGS 84 Earth model (gravity is about 9.78 m/s² at the equator, 9.83 at the poles, and about 9.79 across the UAE); the standard simple pendulum formula T = 2π√(L/g). Walking cadence of roughly 100 to 120 steps a minute comes from research on adult walking by Tudor-Locke and colleagues. Stride length from height and floor heights are rough rules of thumb. Sample data is made up to show how each experiment works.