Distance
How far something or someone has travelled. It’s a scalar measurement, meaning it only has magnitude. In physics, magnitude refers to the size or quantity of a physical quantity without considering its direction.
For example, if I said I traveled two miles to Joe Bloggs's house, that is the distance. However, I did not state the direction: left, right clockwise, anti-clockwise, east, north, west, south. This leads us to our next point in position.
Displacement
Displacement considers both the magnitude and the direction. For example, I travelled five miles northeast to Joe Bloggs's house. Displacement considers how far something or someone has travelled in relation to where it started. It measures the shortest distance between the origin and the destination.
Let’s take a simple example of the difference between displacement and distance. Let’s take the Red Cars' journey from House A (bottom left) to House B (top right). This car travelled 2km through the sequence of street networks, while the Blue Cars travelled 1km as they took a shorter route to get to House B.
However, the bicycle was able to take shortcuts rather than the road networks, meaning its distance was only 800 meters. The displacement for all three vehicles is 800m NE. This is because displacement is only interested in the shortest distance from point A to B, meaning all three vehicles travelled northeast for 800 meters, regardless of their distance.
The final point regarding displacement is that if the origin and the destination are the same, displacement will be equal to zero. Take, for example, the Earth’s orbit of the sun. In 265 days (and a quarter), the Earth orbits the sun once, travelling a distance of 940 million kilometres. But because it ends up at the exact same spot as it started, its total displacement in the 365 1/5 days equals zero.
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