According to Einstein's theory of general relativity, gravity occurs due to the curvature of spacetime. This curvature arises due to massive celestial bodies. When these bodies (neutron stars, black holes, etc.) move around in the fabric of spacetime, gravitational waves transpire. Gravitational waves are giant distortions in the curvature of spacetime due to accelerated masses in the cosmos.
Although first indirectly proposed by Henri Poincare' in 1905, gravitational waves were predicted by Albert Einstein in 1916. And right around 100 years later, gravitational waves were detected by LIGO or better known as Laser Interferometer Gravitational Observatory. LIGO used lasers to detect these waves.
Gravitational waves are significant because observing and studying them can give us information about the most far-reaching mysteries like black holes, supernovae, formation of the universe, etc. They can travel through space where electromagnetic waves cannot.
Gravitational waves have no mass and travel at the speed of gravity which is supposed to be the same as light. Gravity is one of the weakest amongst the four fundamental forces in the universe. Although these are vigorous ripples in the curvature of spacetime, it takes them millions of years to reach Earth. As a result, it becomes difficult to detect these waves. So how did LIGO identify them?
They used lasers to detect these waves. LIGO is a physical experiment and an observatory designed specially to detect gravitational waves. There are two primary research centers in Pasadena, California, and Cambridge, Massachusetts. There are detector sites present at Hanford and Livingston, which make LIGO an observatory. MIT and CalTech are the two universities that operate LIGO.
LIGO consists of two interferometers, both 4km in length. At the ends of the 4km arms are two additional mirrors. Further from the laser is the beam splitter, kept at an angle of 45 degrees.
The laser passes a beam of coherent light that hits the beam splitter. If the lights on both ends are in antiphase, they cancel each other out when merged, resulting in no light (destructive interference). When a gravitational wave passes through these beams, it stretches and compresses spacetime, changing the length of the arms. It leads to constructive interference of light, indicating the presence of the wave. After entering the instrument, the laser bounces between the two mirrors 300 times before merging with the other beam. This design increases LIGO's sensitivity to vibration and helps to detect changes in lengths tinier than a proton! LIGO has had approximately 50 such detections as of December 2019.
But do gravitational waves affect humanity? Are they harmful?
When two black holes of masses merge, they release an enormous amount of energy.
The energy they emit is enough to power the universe thousand times over. The first gravitational wave contained 5.3 × 1047 J of energy. But that was 1.3 billion light-years away, which is why we only saw a tiny fraction of the energy from the gravitational wave. If those same black holes merged at a distance of one light-year away, a vigorous amount of energy would've released. Earth would have stretched and compressed by 20 microns then. Similar to tidal waves that occur due to the Moon although, this process would be much faster. If the gravitational waves are strong enough, they could heat Earth's interior, triggering tsunamis, earthquakes, volcanic eruptions, causing heavy damage.
Fortunately, we need a black hole merger event in our solar system for this to happen. Because of weak interactions, even the gravitational waves from the nearest star would be indistinguishable.
When do you think gravitational waves would affect Earth significantly? Let us know in the comment section below!
Podcast episodes with more info:
Astronomy Cast: Episode 71
Daniel And Jorge Explain The Universe: Episode Gravitational Waves
In Our Time: Science : Episode Gravitational Waves
Some memes :
This article was written by Aninditha Nair.
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Wow, this is so informative & interesting!!
ReplyDeleteAll theory and no proof. This isn't science. It's Science. And I thought the bible was dogmatic🤦♂️
ReplyDeleteYour goals are beyond our understanding and so is the sentence which you wrote.
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