Parabola (noun, “Per-AH-boh-luh”)
A parabola is a specific kind of U-shaped curve. Every point along that curve is the same distance from both a fixed point and a straight line. The fixed point is called the focus, and the fixed straight line is called the directrix. The word “parabolic” describes things that are shaped like parabolas.
When something is thrown up into the air — not straight up and down, but with some sideways momentum — it will take a parabolic path as it sails upward then falls back down. This is true whether you’re kicking a soccer ball or a fountain is shooting out water. Both the soccer ball’s path and the arc of the water will be parabolas.
Some planes fly in parabolic paths. They climb steeply upward then turn sharply to dive steeply down. Such a flight creates a sense of weightlessness inside the plane.
Parabolic mirrors are also useful tools. They focus incoming light into a single point. This makes them good for collecting light in telescopes. It also makes them good for creating sharp beams of light for car headlights, spotlights and lighthouses.
In a sentence
Parabola-shaped flights that create a sense of weightlessness inside a plane can let scientists test how things would behave in zero-gravity — without having to go to space.