To describe the motion of an object, we need a frame of reference. A frame of reference is essentially a set of coordinate axes used to define an object’s position in two- or three-dimensional space. It can also be defined as a set of coordinates used to record the position and time of events. The most familiar example is the Cartesian coordinate system, where an object’s location is specified by three coordinates: x, y, and z.
For a simple real-world example, imagine you’re standing on level ground.Your position on the ground becomes your frame of reference, and anything you observe or measure is described relative to the point where you are standing.
There are many other real life examples of frames of reference, including:
1. Moving Train
Inside a smooth-moving train, you can walk down the aisle as if you are standing still on solid ground. Your motion is measured relative to the train, even though the train itself is speeding relative to the Earth.
2. Rotating Carousel
A merry-go-round brings back many childhood memories. We loved riding them as kids, feeling the thrill as the world spun around us. They’re also a perfect example of a frame of reference. While you’re sitting on a horse, you might feel perfectly still relative to the horse itself. But to someone watching from the ground, you’re actually moving in a continuous circular path.
3. Earth Surface
In daily life, we almost always measure motion against the ground beneath us. When you say you’re standing still, it simply means you’re not shifting position relative to the Earth’s surface, even though the planet itself is spinning and racing through space.
4. Sailing Ship on the Ocean
A sailing ship on the ocean is another good example of frame of reference. For the sailors on deck, their world is the ship itself—they judge their movement by the creak of the boards beneath their feet or the sway of the mast. But to someone watching from a lighthouse on shore, the ship is steadily changing its position against the distant coastline, gliding across the vast blue horizon.
5. Escalator in a Mall
An escalator in a busy mall can play tricks on how we sense motion. As you walk upward on the moving steps, you feel as though you’re simply walking at your usual pace relative to the escalator. But to someone standing on the stationary floor below, you’re moving faster—or slower—depending on whether the escalator is carrying you up or down.
6. Passenger in a Car on a Highway
If two cars travel side by side at the same speed, a passenger might observe the other car as motionless, even though both are moving rapidly relative to the road.
7. Aircraft in Flight
When you’re flying in an airplane, the aircraft itself becomes your frame of reference. Pilots and passengers sense motions like a sudden bump of turbulence or the tilt of a turn only in relation to the plane, even as it speeds thousands of meters above the ground.
8. Orbiting Space Station (ISS)
Astronauts floating inside the ISS feel weightless and may think they are at rest, but they are hurtling around Earth at over 27,000 km/h relative to the planet.
9. Moving Walkway at an Airport
Someone standing still on a moving walkway is stationary relative to the walkway but moving relative to the stationary terminal floor.
10. Hot Air Balloon Ride
If you’ve ever enjoyed a hot-air balloon ride, you know the gentle magic of floating above the earth. Inside the basket, you feel perfectly at rest, as though suspended in a calm pocket of air. But to someone watching from the ground, the balloon is quietly drifting across the sky, carried along by the wind.
11. Swimming in a River
A swimmer may feel they are swimming straight across, but if the river current is strong, their position relative to the riverbank constantly shifts downstream.
12. Watching Football
Here’s another frame of reference example football fans will recognize. When you’re watching your favorite team in action, the TV screen becomes your frame of reference. You observe every sprint, pass, and goal as movement across the field shown on the screen, even though you’re sitting comfortably on your couch.