On the 11th of February 2016, the Laser Interferometer Gravitational Wave Observatory (LIGO) announced that they had detected the first evidence of the existence of gravitational waves the previous September. At the time this was a massive triumph for the team that observed them and made headlines worldwide.
So what are gravitational waves? In 1916, Einstein predicted that massive objects have an effect on the fabric of spacetime itself. As space and time are linked, think of space as a large sheet that the galaxies, quasars and black holes are embedded in. The larger the object, the deeper they are embedded into the fabric.
Gravitational waves themselves are disturbances in this fabric, like ripples in a pond that propagate throughout the universe at the speed of light. The September 2015 discovery were the waves generated at the merging of two black holes more than one Billion light years away.
The black holes themselves were 29 and 36 solar masses. The collision energy would be cataclysmic, even in cosmic terms. Put simply, two subjects 29 and 36 times the mass of the sun collided. The ripples from the collision were detected via the lasers at the LIGO observatory as they passed through the Earth.
Gravitational waves are similar to electromagnetic radiation in the way they propagate through the universe. Optical telescopes can’t really observe these events due to their extreme distance so radio astronomy is used, that is the detection of waves as opposed to a physical view.
Gravitational waves are reasonably well understood due to this discovery although gravity as a whole isn’t. Out of the four forces of nature; the strong force, the weak force, electromagnetism and gravity, gravity is the weakest and the weakest by far.
Gravity in its traditional sense is what keeps the stars orbiting the centre of the galaxy, keeps us on the ground and keeps our planet in orbit around our sun. Although if you lift your arm, you are in a sense overcoming gravity. Gravitational waves aren’t catered for in classical Newtonian physics as they state an event like a black hole merger would propagate waves instantaneously.
These waves don’t interact with the Higgs field, the entity which gives particles mass. The Higgs field along with mass gives a particle its velocity. Gravitational waves along with light have no mass. If no mass there is interaction with the Higgs field, so they can only travel at one speed. As fast as it is possible to go. The speed of light 300,000 km/s.
When laser astronomy becomes more advanced in the future, the waves emitted from orbiting binary stars or even quasars can determine their spin velocity and mass with more accuracy. It could even give us more clues into the formation of the solar system and early universe.
Given the Big Bang occurred more than 13 billion years ago, it will take billions more years until that information can reach us even if it is travelling at the speed of light. We could be waiting a few more billion years to discover more secrets of the early universe. Just one of the times it frustrates me how incredibly vast the universe is.