neon sign comes alive at night.

Red.

Blue.

Green.

Pink.

Orange.

The colors seem almost magical.

But inside every glowing tube is a simple and elegant piece of physics.

Electricity is passing through a gas.

And that gas is producing light.

In Why Neon Signs Glow in Different Colors, we explore the science behind gas-discharge lighting and discover why different gases, coatings, and electrical processes create the brilliant colors we see in illuminated signs.

We begin inside the glass tube.

The tube contains a gas at low pressure.

When a high voltage is applied, electrons accelerate through the gas and collide with atoms.

These collisions transfer energy to the atoms, pushing their electrons into higher-energy states.

But those excited states ...