Exploring the cosmic couch and imagining the wobbly world of gravitational waves is a rollercoaster in spacetime itself. But do you know what exactly it is?
Just imagine you are in your living room sitting on the couch drinking coffee and listening/watching “The star talk show” by Neil DeGrasse Tyson and suddenly it starts juggling like a bowl of jelly. Well of course , we have a double take on it, thinking this is jiggling because Sir Neil is speaking(?)
Ah no wait, it’s the mischievous ripples of gravitational waves. But the kick here is the gravitational waves are not everyday variety waves, traveling at the speed of light and shaking things up like a galactic earthquake. They are so sneaky that even Einstein himself had double thoughts on it.
Gravitational waves are a quest to detect embarking decades of anticipation, but little did everyone know that a historic detection is going to be made. Massive objects like black holes and neutron stars, gel together send gravitational waves rippling through the fabric of spacetime. It’s like watching the universe performing its own rendition of “Dancing with the stars” but instead of jazz music we get mind blowing distortion with the essence of reality.
These ripples are like the cosmic equivalent of dropping a pebble in a galactic pond, causing spacetime to ripple like a celestial trampoline.
A gravitational wave refers to an unseen but extremely rapid disturbance in the fabric of space. These waves propagate at the same velocity as light, which is 186,000 miles per second. As they traverse, these waves cause compression and elongation of objects encountered along their path.
The first detection of a gravitational wave was in 2015. LIGO spotted a wave sweeping through the earth. It uses laser beams fired over distances of 4 km to detect slight shifts caused by passing waves.
LIGO stands for Laser Interferometer Gravitational Wave Observatory. Its a groundbreaking experiment based on detecting gravitational waves. If we explain it in simple language, LIGO is basically humanity’s super sensitive cosmic eavesdropper, listening in on the whispers of the universe and unlocking its deepest secrets. One gravitational wave at a time, pretty rad lol.
Since the first detection in 2015, LIGO is like a small kid in a candy store looking for new goodies that come up like collision of black holes, merger of neutron stars and even mysterious signals from depth of space.
The first-ever gravitational wave detector could fit atop a large dining table. This was the Weber bar — literally a large and heavy chunk of metallic cylinder, usually aluminum, named after its inventor, University of Maryland physicist Joseph Weber.
These bars had a finely-tuned resonance frequency of around 1 kilohertz. Weber bars worked on the principle that any vibrations caused by gravitational waves would disturb the resonant frequency and be measurable using piezo-electric sensors. In reality, the huge surplus of environmental vibrations and thermal noise meant that even more advanced heavier and cryogenically cooled bar detectors never achieved the sensitivity to detect gravitational waves.
A unique way to try and detect gravitational waves as a ‘by-product’ sending and receiving radio pulses from interplanetary spacecraft such as Cassini (Saturn) and Juno (Jupiter), and checking whether there is any deviation from the expected spacecraft location. These essentially act as an interferometer with one arm, making it a neat way to utilize the space probes during their decades-long travel time across the solar system.
Another indirect way of detecting gravitational waves is by monitoring the precise astrometry or positions of stars in sky surveys such as Gaia. Given how precise these surveys are, any correlated perturbation in the sky position of stars due to gravitational waves could be potentially detectable.
The detected wave resulted from two black holes as they spiraled towards each other. This event generated powerful disruptions in the fabric of spacetime. At its peak, the collision released energy surpassing the combined energy of all stars in the cosmos.
This groundbreaking observation answers a lot of long-held questions we have had about the universe and opens up a lot more questions, too.
Signing off once again,
Not your everyday space enthusiast,
Devarshi Trivedi.