So continuing from last blog, I would like to elaborate more on Gravitational waves in this blog; what exactly are they? How useful this current discovery mean? How could they be pioneered to understand the universe? And why it took so long to physically detect them by LIGO?
So let’s start.
As explained previously that Gravitational waves are nothing but ripples in space-time fabric generated through some violent movements or explosions (Which considering the vast span of universe is norm, but to be able to evidence the same is not that common). Einstein has shown the same mathematically in 1916. Also it stated that these waves travel at light speed and carry significant information of the event which has given birth to the waves. These events could be anything like supernova death of star, colliding of black-holes, “brotherly hug” of neutron or white dwarf stars, wobbly rotation of binary stars and also gravitational radiation created by birth of universe itself.
In fact, in 1974, two astronomers working at Arecibo Radio Observatory had successfully observed the binary stars movements in accordance with Einstein’s theory and hence proof of the existence of Gravitational waves. More studies have also been made into successfully predicting similar effects, but all such proof were, in one sense, mathematical and more of an indirect evidences. Scientists around the world were keen on gaining “physical” proof.
So what’s so important about detecting the waves? To understand the deep mysteries of the universe has always been captured the mankind’s attention since the evolution of Homo sapiens sapiens or may be even before that in whatever half-intelligent Genus we all belong to. More astrophysicists and astronomers explore and understand about universe on behalf of entire humankind, more unsolved mysteries are cropping up. As if span of the universe itself is not doubtful enough, scientists don’t have clear picture of the birth of universe also. Gravitational waves are not electro-magnetic radiation. They are in complete different league; whole new phenomena. They carry information which was not measurable before. They have tendency to travel without any interaction with matter and hence retaining the “purity” of the event. Hence it is becoming so much important to take it up the study of the waves to dive deeper into depths of unknown; in search of those brightly shining but hidden pearls of wisdom.
As per theory, any moving object is source of Gravitational waves; even on earth whether it’s ball pitched at high velocity by pitcher or bullet fired or spinning top or newspaper thrown in your verandah with ferocity of the daily boring job; practically everything. But as noted before, considering heavenly objects for which Einstein’s theory specialized for, numbers generated by this relativity equations via such miniscule objects are negligible. Waves are so weak that you can pretend that they are not present at all. And hence scientists all over the world had to rely on massive movements outside our world. Even those waves, while reaching to earth are faded out, needed very precise and efficient carefully built experimental instruments to measure them. One of them is LIGO which stands for Laser Interferometer Gravitational-Wave Observatory. You can find all the information related to LIGO and science behind the architecture at https://www.ligo.caltech.edu/page/ligo-gw-interferometer .
So not going much detail into how exactly LIGO managed to detect gravitational waves after almost 100 years (It will require much detailed scientific setup of LIGO. Refer above given link & a picture), I would like to wrap up the blog with brief mentions of types of gravitational waves. Based on characteristic vibration signature waves are categorized as below:
- Continuous Gravitational Waves: It is generated by single spinning object, say Neutron star. They are mostly constant in their properties such as frequency and amplitude.
- Compact Binary Inspiral Gravitational Wave: As name suggests, these waves are created by binary stars. Actually it could be either binary Neutron stars or Binary black holes or mixed-doubles like Neutron star-Black hole. Whatever be the source, one fact is observed by scientists that due to losing energy with each spin, both spinning object come closer which again increases the gravity and spin; ultimately make them spiraling into each other with cataclysmic crash at climax.
- Stochastic Gravitational Waves: Frankly speaking these waves are nothing but same as your transistor radio tuned to no particular station but just emitting noise. But these noise here could be from the time when time started its existence i.e. Big Bang. They are small, random, ever-present and difficult to distinguish but most desirables.
- Burst Gravitational Waves: These waves are ghost. There is no model or signature to define them and hence no particular methodology. It’s like searching something but you cannot name what it is. They have utmost potential to reveal something which has always been “holy grail” of human conscience.
Further Reading reference: