ABCs of gravitational waves

Scientists said on Thursday they have for the first time detected gravitational waves, ripples in space and time hypothesized by physicist Albert Einstein a century ago, in a landmark discovery that opens a new window for studying the cosmos.

Discovering gravitational waves would be a huge deal for physics, cosmology, and our understanding of the universe at large. But if you're not a scientist studying one of the aforementioned fields, it's possible you've never heard of these mysterious ripples. So what are gravitational waves and why is the discovery so significant?

Visualization - Gravitational waves generated by a binary system. [Photo/NASA]

What are gravitational waves?

Gravitational waves are disturbances in space-time, the very fabric of the universe, that travel at the speed of light. The waves are emitted by any mass that is changing speed or direction. The simplest example is a binary system, where a pair of stars or compact objects (like black holes) orbit their common center of mass.

We can think of gravitational effects as curvatures in space-time. Earth's gravity is constant and produces a static curve in space-time. A gravitational wave is a curvature that moves through space-time much like a water wave moves across the surface of a lake. It is generated only when masses are speeding up, slowing down or changing direction.