Friday the 11th of February marked the dawn of a new era in observational astrophysics as the collision of two black holes, about a billion light years away, created a violent storm in the fabric of space-time that was visually spectacular.
The resulting gravitational waves were detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO). Observational Astrophysicists, as well as others in the wider scientific community, were jubilant following the announcement of the collision and consequential wave detection on Friday the 11th of October, made by David Reitze, executive director of LIGO. Whilst this validates ideas which are the foundations of general relativity – a theory first proposed by Albert Einstein a century ago – that is not where the significance of this finding lies; at least not for me.
The two black holes that LIGO detected were colossal; one was about 36 times the mass of our sun whilst the other was 29 times that mass. For anyone who’s curious, the mass of the sun amounts to almost 2 x 10^/30 kg. As a result of the collision, the two black holes merged to create a black hole 62 times our sun’s mass, whilst the residual mass from that collision – which corresponded to 3 times the mass of the sun – was converted into the energy that propagated the gravitational waves.
“Two black holes merged to create a black hole 62 times our sun’s mass”
According to Alberto Vecchio, a physics Professor at the University of Birmingham, as well as a researcher at LIGO, the detection of gravitational waves is significant because “We have observed the universe through light so far… Gravitational waves carry completely different information about phenomena in the universe”. He’s not wrong. Our perception of the universe has thus far relied on the waves of infra-red, visible light and radio in the electromagnetic spectrum, which has limited our observation of the universe. This is because the universe was opaque to light from its inception 400,000 years after the Big Bang. In the foreseeable future I imagine gravitational waves will be used by observatories to increase our understanding of black holes by exploring their features. Eventually physicists will have the ability to accurately reconstruct the birth of the universe, by detecting gravitational waves from the Big Bang.
Renowned theoretical physicist, and director of the Origins Project at Arizona State University, Lawrence M. Krauss wrote an op-ed for the New York Times which shed some light on the technicalities of the experiment. Two “mammoth” sized detectors were each built separately in Washington State and Louisiana respectively. Each detector consisted of two tunnels that are 2.5 miles in length and perpendicular to each other. He explains that “If a gravitational wave from a distant galaxy traverses the detectors at both locations roughly simultaneously, then at each location, the length of one arm would get smaller, while the length of the other arm would get longer, alternating back and forth.” An obvious obstacle that presented itself during the experiment was that physicists had to be able to measure a periodic difference in the length between the two tunnels by a distance of less than one ten-thousandth the size of a single proton to detect the signals from the gravitational waves.
This discovery has monumental ramifications intellectually but more so existentially. It will help answer one of the most fundamental questions that has burned into the collective consciousness of our civilisation: how did the universe come to be from nothing? By presenting us with the potential to travel back in time to that instantaneous singularity when everything began, it could also provide further insight into the nature and existence of ‘god’. I don’t know about you but personally, I find that incredibly fascinating, and apparently Lawrence Krauss agrees. In the same New York Times Op-Ed he wrote, on the purpose of the experiment, that “Such pinnacles of human creativity change our perspective of our place in the universe”.