How It Works
Light bulb, with white glow on a blue background.

The speed of light

Light bulb, with white glow on a blue background.

Travelling through a vacuum, light zips along at just under 300,000 kilometres (just over 186,000 miles) per second. Almost all particles in our universe contend with the Higgs field, which interacts with them to give them mass.

Photons – the particles which make up light – are the exception. They don’t interact with the Higgs field and therefore possess no mass. This means that no energy is required to change their velocity and there is no limit to their speed.

So why is 300,000 kilometres (186,000 miles) per second the cutoff? This is simply a fundamental property of our universe, a constant set in stone when the cosmos came into being.