What Is Pi? (Grades 5-8)

This article is intended for students in grades 5-8.

Pi is a number. You may know it as 3.14 or the symbol π. But it’s much more than that!

Pi is a irrational number. This means that it lasts indefinitely and never repeats its sequence of numbers. Pi has been calculated to over a trillion digits! But NASA scientists and engineers use far fewer numbers in their calculations. Usually the 3.14 approximation is quite accurate.

Pi is the circumference of a circle divided by the circle diameter. Pi is the same for any circle, no matter its size. It is a mathematical constant.

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Words to know

irrational number: a number that cannot be expressed as a simple fraction

circumference: the distance around a circle

diameter: the distance of a straight line passing through the center of a circle

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Pi is used in many ways. This is fundamental for calculating anything that involves circles, curves or spheres. It is used in geometry, physics, engineering and even computer science.

NASA missions depend on pi. Let’s look at some examples.

Astronauts returning from the International Space Station use parachutes to slow their spacecraft for a safe landing. But how big should the parachutes be? NASA uses pi to calculate the circular area needed to slow a spacecraft as it moves through the atmosphere.

Planetary scientists use pi to learn about the materials inside a planet or asteroid. They use pi to determine the volume of the object. Combined with the mass of the object, they can determine the density of the object. Since we know the densities of planetary materials like rock, ice, and metal, scientists can make educated guesses about the possible composition of the planet or asteroid.

Did you know that spaceship fuel tanks are usually shaped like a sphere? Rocket scientists use pi to determine how much fuel a spacecraft will need. They also use pi to calculate how much fuel is available in spacecraft tanks and how quickly that fuel flows through their cylindrical fuel lines.

To learn how Pi is helping NASA explore our planet and beyond, check out 18 Ways NASA Uses Pi.

Are you interested in a career that uses Pi? Many different professions use this mathematical marvel. Here are some examples:

• Manufacturing Technician: Turning designs into reality requires skilled technicians. The manufacturing and assembly of robotic equipment and spacecraft parts often involves curves that must be calculated precisely. Being able to follow complex instructions is essential. Trade school training and skills such as operating forklifts and heavy machinery may be required.
• Pilot of the Mars rover: Driving a rover on Mars is not like driving a car on Earth. There are no steering wheels on Mars rovers. Instead, operators on Earth send commands to the rovers. These can include spinning wheels or moving a robotic arm, and these functions use degrees calculated using pi. College degrees in robotics and software engineering could lead to this career.
• Planetologist: What are the objects in our solar system made of? And where do planets, moons, asteroids and comets come from? Planetary scientists use pi to answer these questions and more when studying our celestial neighborhood. A college degree is essential to being an expert in this field, but fields can vary from physics to astronomy to even geology.

How many decimal places of Pi do we need anyway?
NASA Pi Day Challenge