What is a Galton Board?
A Galton board is a simple machine that drops balls through rows of pegs. Every time a ball hits a peg, it bounces left or right.
When many balls fall, most land near the middle and only a few reach the far edges. That makes the familiar bell-shaped pattern you see at the bottom.
Why it matches the binomial distribution
If each bounce is equally likely to go left or right, then a ball experiences a sequence of independent Bernoulli trials. After n rows, the probability of ending in bin k is:
P(X = k) = C(n, k) / 2n
Here C(n, k) counts how many distinct left-right paths lead to that landing bin. With 8 rows there are 28 = 256 possible paths, and each bin gets a share based on its coefficient.
What is Pascal's triangle?
Pascal's triangle is a number pattern. It starts with 1 at the top, and each new number is made by adding the two numbers above it.
On this board, row 8 is 1, 8, 28, 56, 70, 56, 28, 8, 1. Those numbers tell you how many different paths can end in each of the 9 landing bins after 8 bounces.
How to read this simulation
One run can look a little messy because you only dropped a limited number of balls. If you run it again and again, the bars will settle into a smoother middle-heavy shape. The reveal helps you compare the random result with the exact path counts underneath.