There is another historic announcement from the astronomy community today, with the first detection of the gravitational wave background.

Our current best theory for explaining gravity is the general theory of relativity, created by Einstein (and arguably by Hilbert at the same time), in which what we perceive as the force of gravity is actually a warping of spacetime itself. One of the predictions of Einstein's theory is that when a system changes, such as a massive object moving or two objects colliding, they cause the shape of spacetime around them to change as well. This change then starts to propagate away from the system, in a similar manner to ripples in a pond that propagate away from a stone that has landed in the water. These spacetime ripples are known as gravitational waves.

Although scientists have previously detected gravitational waves from major events, such as the collisions of neutron stars and black holes, they have never before been able to observe the much weaker waves that were believed to have been created by supermassive black holes that exist through the Universe. These waves are too weak, and have frequencies lasting over several decades, making them very difficult to ever detect.

Now, long-term observations have finally confirmed their presence.

In a highly anticipated announcement on Wednesday (June 28), teams of scientists from around the world have reported the discovery of the "low pitch hum" believed to be from these cosmic ripples flowing through our galaxy.

At this point astronomers cannot definitively state what's causing this low frequency signal, but it is consistent with theoretical expectations of gravitational waves emerging from copious pairs of supermassive black holes, each weighing the equivalent of billions of suns.

While previous detections of gravitational waves utilized large interferometers on Earth, a different approach was necessary for this study. In order to detect the gravitational wave background, astronomers studied fast-spinning stars called millisecond pulsars, which are dead stars that spin at close to a thousand times per second with very precise regularity, generating beams of light from their magnetic poles, which can then be detected by telescopes on Earth.

However gravitational waves that pass between the pulsars and the telescope will stretch and compress the space-time fabric, causing these very precisely times pulses to shift in time by anywhere between tens of nanoseconds to several years, resulting in the light flashes arriving earlier or later than expected.

The signals of gravitational waves can then be determined by those differences. This is the first time that scientists have found compelling evidence for such patterns of inconsistency etched by a backdrop of gravitational waves.

It is an interesting result, and one that both theoretical physicists and astronomers have been seeking for a long time. It should also permit us to study the properties of such supermassive black holes, and perhaps even learn more about the underlying theory of gravity.

For now we can celebrate this great achievement, and eagerly await the discoveries it will bring in the future.