How much ever we try, there seems to be no way to know what exactly happened during the big bang 14 billion years ago. It remains a mystery, how this perfect geoid, that’s one of its kind, got formed and evolved into something we see today.
Till today this expanse is being measured by NASA spacecrafts such as the Hubble Space Telescope or the Spitzer Space Telescope yet we know so little about it.
Even when the Scientists at Geneva tested the big bang that created headlines, it was barely an attempt made to understand how the universe could have developed from a very tiny, dense state to something so vast.
The initial dense plasma comprised of many charged particles ranging from electrons, protons and photons that bounces off the other particles furiously as there is no way to escape.
Packet photons mean that light was also trapped and hence, humans cannot study anything that lies before the cosmic expansion.
All that we know today comes from the leftover radiation from Big Bang i.e., cosmic microwave background that can be seen via telescopes.
But when the Universe began to expand in ways and lose its density, the photons got the opportunity to escape, yielding the light to travel freely in all directions.
Therefore, the actual process has been shielded against human perception and we have no way left to even believe what happened back then.
Fortunately, Human curiosity and innovation knows no bounds.
There have been several ongoing attempts to ‘listen’ to the Big Bang using cosmic gravitational waves, also called ripples in fabric of space-time.
These waves were predicted by Einstein under his theory of general relativity over a century ago. They were first detected by LIGO in 2015 when two black holes collided.
This needs detection of ultra-high frequency waves emanating from various processes in the Universe like colliding black holes, neutron stars or supernovae (massive stars exploding towards the end of their lifetimes) formation.
Simply, when Light cannot be a messenger to us in crisis, we need to look for another savior: Gravity, using Ligo (US-based Laser Interferometer-Wave Observatory) or Virgo interferometers.
It is ironical and breath-taking that a machinery with just 4kms arm length can listen to something that comes from so far away.
The cosmological gravitational waves reach us from all possible directions and not from the dedicated direction they were produced. This makes the difficult to detect.
Why we are hopeful of these waves telling us about the hidden past?
Universe must have likely undergone through several phase transitions, from explosions to expansion.
Something in the process must have produced these waves like axions (constituting the dark matter) which is yet undiscovered.
It can also answer certain other questions: how strong was the signal?
How far these waves had to travel to reach the Earth?
What constitutes the Universe?
or for instance, how quickly the Universe is expanding now?
Cosmos is supposed to be loosening on its expansion, as the energy triggered by big bang has reduced in time. But in 1998, scientists believed in some dark energy that’s propelling an ever-increasing rate of expansion now.
Most of gravitational wave detectors basically focus on low frequencies because of the fact that the wavelength of any produced wave is directly proportional to the “size” of the universe.
This means a wave that was produced earlier will have comparatively smaller wavelength and higher frequency, than the subsequent others.
Even other hypothetically existing entities like Boson stars, origins and distributions of dark matter through time can also be measured using this probe.
From cosmology’s perspective, history started with the Big Bang. We will not ever know what happened before.
And while the proof of gravitational waves may pacify this argument, it allows to linger around the above unsolved mystery.
Yet today, we have begun to gain an unprecedented envisage at what happened after the Big Bang.