Light is complicated as it can act as both a wave and as a particle.

A particle of light is known as a photon. These can be thought of as little packets of light, carrying energy. When we take a photograph on a modern camera, or on a telescope camera, we count these photons. The more we count the brighter an object is - we call this measurement the flux.

When light acts as a wave, it still carries energy, but it has a bunch of other information too. This helps us to understand more about it.

Every wave (e.g., light, water, or sound) has the following features:

What is Interferometry?

Interferometry is a technique used by scientists and engineers. Tools called interferometers add together 2 or more waves of light. When they do this, the waves of light interact (or interfere) with each other. This can add the waves together, making them brighter. It can also cancel the waves out. Interference only takes place if the waves come from the same object or have the same frequency. We call these types of wave coherent.

The SKA will be the world's largest radio telescope. It is not 1 dish, but thousands of radio antennas that all work together. It will be 50 times more sensitive than any other radio telescope. It will survey the sky 10,000 times faster than ever before.

The Extremely Large Telescope (ELT) will be the world's largest optical telescope. The telescope is being built by the European Southern Observatory (ESO). The ESO is made up of 16 countries which includes the UK and Ireland. The ELT is due to be complete at the end of 2027.