Every year Pi () day is celebrated on the 14th of March, allowing people throughout the world to throw a party for this superstar number. The reason that Pi Day falls on the 14th of March is because the date of (3.14) can be written as the first three digits of Pi when following the U.S. convention of (month/date). If you want to celebrate by decorating your classroom, office or even living room, then make this super easy Pi Day Sphere Bunting.

## How To Make a Pi Day Sphere

Watch the video or read through the steps below.

### Step 1

Draw 10 identical circles by using a pair of compasses or by drawing round a circular object. Alternatively print off this Pi Day Sphere Worksheet which can be used in the classroom or at home. The sphere in the worksheet has a diameter of around 5cm, but you can make your spheres as big as you like. Decorate the circles to celebrate Pi Day. Your imagination is the only limit!

### Step 2

Cut out the decorated circles.

### Step 3

Fold each circle in half, with your design on the inside of the fold.

### Step 4

Take a circle and put glue on one half of the undecorated side. Stick this glued half to an undecorated half of a different circle. (You are never putting glue on your decorated sides!)

Continue gluing the undecorated halves of different circles together, creating a fan effect. Do this until you only need to glue one final side.

### Step 5

At this stage add a string down the middle of your sphere and glue the final sides together. Your Pi Day Sphere is complete! If you are a teacher with a class of 30 pupils, you should now have enough spheres to string together to make some impressive looking bunting.

## Other Ideas for Your Pi Day Sphere Craft

• You don’t have to use 10 circles; you could combine different numbers of circles and see what works best.
• Experiment using different colours of paper.
• Use your paper sphere as a handy revision guide – write a key fact on each circle and then leaf through it like a book.
• Keep your Pi Day sphere to hang on your Christmas tree.

## Handy Facts About the Sphere

Here are 10 handy facts about spheres to think about while you are making your Pi Day Sphere craft.

1. A sphere is the set of points that are the same distance from a point (known as the centre) in 3-dimensional space.
2. The volume of a sphere with radius is .
3. The surface area of a sphere with radius is , a formula which was first found by Archimedes.
4. The sphere has the lowest surface area to volume ratio of any solid shape. This means that for a given volume, a sphere has the least amount of surface area possible.
5. This special surface area property means that lots of spheres appear in nature – bubbles are spherical because they need the smallest possible surface area to get the lowest amount of surface tension.
6. A hemisphere is exactly half of a sphere.
7. A sphere only has one surface and no edges or vertices.
8. A sphere with centre and radius has the equation .
9. Planet Earth is a Spheroid, which means that it is not quite a sphere.
10. Here is a picture of Einstein reflected in one of the most accurate spheres ever made. It only differed from being a perfect sphere by the size of 40 atoms.

Article by Hazel Lewis