Big Bang: What happened 14 billion years ago at the beginning of the universe is one of physics’ greatest mysteries. There’s no easy way to prove it. This is because, in its earliest stages, the universe was filled with dense plasma. It was a gas composed of charged particles, including electrons and protons (particles that comprise the atomic nucleus along with neutrons). Photons (particles of light) were trapped in this mixture and collided with other particles, as there was no way out.
As the universe expanded and the density dropped significantly, photons eventually found a way out and light began to travel freely. This event, called recombination, occurred 380,000 years after the Big Bang. It gave rise to the first snapshot of the origin of the universe (the cosmic microwave background) that we see with telescopes.
Everything we know about the early universe is based on leftover radiation from the Big Bang. But recombination acts like a wallop. We can’t directly probe earlier epochs with a telescope. Because at that time, the light was stuck. Now several projects are trying to listen to the Big Bang using gravitational waves. These are woven into the fabric of space.
Our new project will aim to detect such waves at ultra-high frequencies and could lead to the discovery of completely new physics. The recent discovery of gravitational waves by the LIGO/Vargo experiments has opened a new window of observation on the universe. They enable us to investigate phenomena in which gravity, rather than light, is the messenger.
What has been discovered so far to know more about the Big Bang and the events before it took place
Gravitational waves discovered so far are called astrophysics gravitational waves. They are produced by relatively recent physical processes, such as the merger of black holes. The type of waves that originated in the early universe is called cosmological gravitational waves and have not yet been detected.
Such waves travel independently after they are generated. They can travel across the recombination wall and provide a unique tool for probing the early universe. Whereas astrophysics gravitational waves come from a precise direction in the sky, Cosmological waves reach us from all possible directions, corresponding to different regions where they originated in the past. This makes them very difficult to detect.
Processes involving hitherto undiscovered particles such as axons (which can make up dark matter) could also produce the waves. So if cosmological gravitational waves are detected. They could give us important information about what happened at the beginning of time.