There have been waves of excitement amongst the scientific community since LIGO (The Laser Interferometer Gravitational-Wave Observatory), announced the detection of gravitational waves. The 45-year-old project, having had a 5-year $200 million overhaul, proved its worth same month. On September 14th 2015, LIGO’s automated systems detected gravitational wave signals from a black hole binary system (two black holes orbiting one another) merging as one. The event itself is not particularly special in its own right; it is calculated that they happen somewhere in the universe every 15 minutes. What was special about this merger was that it had the right magnitude and occurred in the right place and the right time for LIGO to be listening.
So now that we have heard LIGO, what is it saying?
“With this discovery, we humans are embarking on a marvelous new quest: the quest to explore the warped side of the universe — objects and phenomena that are made from warped spacetime. Colliding black holes and gravitational waves are our first beautiful examples,” — Kip Thorne, theoretical physicist and LIGO co-founder.
The electromagnetic spectrum describes photon radiation from radio waves to gamma rays. The image of this spectrum would be familiar to most from science in school; recall the small section that lies in the middle representing visible spectra, the light that we can see. Telescopes work by detecting such electromagnetic waves and from them constructing images, which we can use to assemble maps of the universe. For instance we can paint a picture of the universe by mapping infrared waves, gaining information about temperature that we cannot see otherwise. “Gravitational waves provide a completely new way of looking at the universe,” says Professor Stephen Hawking, and that is by listening to it.
“We can now hear the universe,” says LIGO physicist and spokesperson Gabriela Gonzalez, “the detection is the beginning of a new era: The field of gravitational astronomy is now a reality.” It is theorised that cosmic phenomena will generate different frequencies of gravitational waves; as a result, we would be able to ‘see’ phenomena that would otherwise be hidden from all our existing telescopes, revealing a once dark universe. The aforementioned two black holes colliding, would not produce significant electromagnetic radiation, but a huge gravitational wave signal. Ultimately, we can use this to produce a gravitational map, painting a picture of transient events; supernovas, black holes and who knows what else…
What this marks is a new and exciting era in astrophysics and cosmology, which young physicists are poised to appreciate. Many physicists are now hoping for LIGO to detect gravitational waves from merging neutron stars. These are the smallest and densest stars known to exist in the universe and are much too dim for current telescopes to gain useful information. As the name suggests, they are composed entirely of neutrons and can result from the gravitational collapse of massive stars. Merging neutron stars are interesting because they are thought to fuse light elements into heavier ones, which then spill into the surrounding environment. These collisions are thought to be the source of the much heavier elements we have, like gold.
Excited scientists the world over are hoping that gravitational wave astronomy will help reveal some of the universe’s best-kept secrets. Do neutron stars have an asymmetric distribution of mass? Do gravitational waves travel at the speed of light? Considering that two black holes merging produced these waves, can we describe their evolution? What is space-time made of – is it cosmic strings? What makes stars explode? At what rate is the universe expanding? The list goes on.
But what do gravitational waves mean for those outside of the scientific community? At this moment in time, probably not very much, but perhaps this is to be expected considering the history of scientific discoveries. When Wilhelm Roentgen found X-Rays in 1895 their future significance in diagnostics would not have been known. Similarly, when Heinrich Hertz confirmed James Clerk Maxwell’s electromagnetic equations by producing radio waves in 1887, the vast array of uses they have now could not have been foretold. Only time can tell how uncovering these new, gravitational waves, can become integral to our lives.
Fariha Azad is a Maths and Physics student at Warwick. She also writes for Warwick Finance Societies’ Market Wrap Up.