By Adelle Rodda
Last week we began the story of the origin of the Universe. In case you missed it you can read it here or if you can’t be bothered below is a quick summary:
Once upon a time, some 13.8 billion years ago, a searingly hot, subatomic speck that held the entire contents of space – in the form of pure energy – within it sprung forth. Then, while still in its infancy, this speck had a dramatic growth spurt – known as Cosmic Inflation – swelling to 100 trillion trillion times its original size, in less than a fraction of a second. After this growth spurt the Universe continued to expand but at a much slower rate. Space cooled, allowing particles to form and then join together to build stars, planets, and all the other stuff in existence today.
The recently discovered ripples, or gravitational waves in space-time are the first direct evidence that Cosmic Inflation – the Universe’s growth spurt – actually happened all those billion of years ago.
So what exactly are these cosmic waves and how are they proof of Inflation Theory?
When scientists have a theory they think about the consequences that would arise if such a scenario had taken place. Then using lots of intense maths they make predictions about what evidence should exist in order to prove their theory correct.
So scientists predicted that if Cosmic Inflation really happened, then the force of such a rapid expansion would have caused gravitational waves to propagate throughout space-time and these effects that would be visible in the Cosmic Microwave Background.
Imagine dropping a boulder into a calm lake, the impact would cause ripples to spread out across the lake’s surface – this is kind of what happened during Cosmic Inflation, but way more complicated…
Space and time are not separate entities. They are woven together like a “fabric”, which spreads throughout the Universe. A commonly used analogy is of space-time being like a stretched out rubber sheet. If you were to roll a ping-pong ball across that sheet it would travel in a straight line. Now if a bowling ball were placed on that rubber sheet and you tried to roll the ping-pong ball across it, the ping-pong would travel in a curved path towards the bowling ball – because of the dent caused by the bowling ball’s weight.
This is essentially what gravity is – the attractive force that results from bodies, like stars, planets, and bowling balls warping the fabric of space-time. It’s the reason that the moon orbits around the Earth and the planets orbit around the Sun.
The gravitational waves produced by Cosmic Inflation have continued to ripple their way through space-time – like ripples across the surface of a pond – and as they travel through space they cause things in their path to expand and contract.
Although gravitational waves themselves can’t be seen, the effect they have on objects in their path can be. The “footprints” of gravitational waves can be seen as a distinct pattern – scientifically known as B Mode polarization – in the earliest light emitted from the Big Bang. Scientists have been scanning the skies for a long time to catch a glimpse of this evidence of Cosmic Inflation and last month researchers working on an experiment called BICEP2, claimed to have spotted it.
The discovery – if proven correct – is strong evidence that Cosmic Inflation actually happened and perhaps brings us closer to understanding the most fundamental question of all – where do we come from?
Astrophysicists are so smart.
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