Our universe is ruled by four fundamental forces, electromagnetism, the strong nuclear force, the weak nuclear force, and gravity. While others are understood well and have been experimented upon numerous times, gravity is still a mysterious force. For over a century we believed the proposed explanation of gravity by Sir Isaac Newton was accurate, and the theory of Gravity by Albert Einstein was dismissed, in 2015, researchers detected the gravitational waves which obeyed the rules of explanation presented by Albert Einstein.
Sir Isaac Newton’s Gravity
All of us are familiar with the famous event that led Newton to discover gravity, while it may have not transpired in an exact manner, the fundamentals of gravity were cemented. He stated that an attractive force exists between each particle in the universe that pulls on each other without any contact, the smaller object is drawn towards the larger body because the latter exerts a greater force because of its mass. This is the exact reason why when we throw something in the sky it falls back on the surface of Earth. This law also explained why our planets orbit the Sun.
However, in one lecture and explanation, he stated that if our Sun was to simply disappear then Earth, along with other planets would instantaneously fly off into space. This was considered to be true for many years, but Einstein didn’t agree with it.
Albert Einstein’s Gravitational Waves
After many years of contemplation and theorizing, he came up with the fact that nothing can travel faster than light, not even gravity. He argued that if nothing can travel faster than light, how come we’d face the consequences of lack of gravity by the Sun before being engulfed in darkness? This led him to theorize a new way to look at gravity. After 10 years he finally came up with the solution, he proposed the universe to be in 3-dimensional fabric with 1-dimensional time which came to be known as space-time fabric, and the mass of different bodies curves this fabric to varying degrees. Just like a ripple is created as we throw a pebble in the water.
By putting Earth in a similar situation now, if Sun was to disappear we’d see its light gone first, followed by the ripple or wave created by its disappearance.
LIGO Gravitational Waves
LIGO stands for Laser Interferometer Gravitational-wave Observatory, it is one of the largest wave observatories in the world and is nothing short of an engineering marvel, it will become more evident why as we continue to understand the feat that has been achieved by it. It was done by using laser and not just any lasers, specifically designed lasers that maintain a single wavelength and to mitigate false detections from local traffic or earthquakes, two observatories have been built on separate locations and gravitational waves can be observed at the same time on both locations. One observatory is located in Livingstone and another one is at Hanford.
The way these lasers work is that they have an L-shape structure with each vacuum tube spanning out to 4 km, this might seem like a lot of area for lasers to work but detecting these waves is not an easy task, and the longer the length the better it will be able to detect. These are made up of steel and are sheltered by 10 feet wide and 12 feet high concrete walls. Additionally, the laser that is produced must be of one wavelength, because if it alters in wavelength no accurate measurement can be detected, and to produce the desired accuracy two mirrors are placed on either side of the vacuum tubes. These mirrors weigh 40 kg each and are one of the smoothest mirrors on the entire planet. While the ‘O’ stands for an observatory in its name, LIGO has no relation or link when it comes to finding any sort of light, it is blind. Because gravitational waves are not part of the entirety of the light spectrum.
Now comes the absurd part, the detection that was made by LIGO was sourced from a ripple in space-time fabric created by two giant black holes merging into one around 1.3 billion years ago, it makes us think just how far these black holes must’ve been for us to detect it after such a long time. Even though black holes are one of the most extreme things in the universe, the gravitational ripple created by them is still painfully difficult to detect, after traveling for so long these waves lost most of their strength and were extremely faint. To put this into perspective, if we consider the distance from Earth to Alpha Centauri which is about 4.367 light-years, and the equivalent of this detection would be to detect a variation in that distance about the thickness of a human hair. Our minds don’t even begin to comprehend such unimaginable measurements yet it was made possible, thanks to LIGO, and this motion between the mirrors was just 10 to the minus 18 meters.
Ultimately, it is now well established that both of the theories of gravity were accurate. While Newton’s idea of gravity helps us understand the mechanics and its effects on the surface of Earth, Einstein’s theory of gravitational waves proves accurate on a grander scale. Now LIGO has undergone many updates and is considered as Advanced LIGO, scientists say there will be more updates in the future.