001 : Peering into the Big Bang

THE COSMIC MICROWAVE BACKGROUND RADIATION (CMB)

is the farthest we can see into the past. The image from WMAP above, shows the relative differences in temperature of the universe about 380,000 years after the Big Bang. At this point, the universe was a soup of plasma too hot for atoms to form. Electrons whizzed around nuclei knocking photons in all directions; it was a mess. There is an issue here in terms of observations. Namely that the CMB forms a wall which effectively destroys any information about what happened before this from getting through. Regardless of our technological progress, we simply cannot gain any meaningful data beyond this barrier via light (electromagnetic radiation or EM). A possible solution may be looming over the horizon, and I believe that we are entering into a new age of astronomy. The answer may lie with one of our most newly harnessed tools; gravitational waves (GW).

Ripples in Spacetime

Let’s take a step back for a moment. What are GWs? They are ripples in spacetime caused when massive objects, such as black holes and neutron stars, interact. In February of 2016 the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced the first observations of GWs. Namely, in a cataclysmic event 1.3 billion years ago where two black holes, 29 and 36 times the mass of the sun merged in a fraction of a second. As an aside, this was yet another confirmation of Einstein’s general theory of relativity, published a hundred years prior. Since this first observation, several more have been discovered in relatively quick succession. At the time of writing, there have been six GW observations, including a binary neutron star merger. It has been postulated that discoveries like this will be commonplace in the near future and is reminiscent of the discovery of exoplanets that began in the early 1990s. The rate of discoveries grew exponentially from then and now we know of more than 3,500 exoplanets.

New way of "seeing" the universe

EM gives us many different paths for discovery. Take for example the images above of Andromeda, our nearest galactic neighbour. Each frequency tells a different story, uncovering different phenomena in each part of the spectrum. For example, when viewed in visible light, the rings appear to be spiral arms, however in ultra-violet and infrared they closely resemble a ring-like structure. This has been used to suggest that Andromeda was involved in a direct collision with its neighbour M32 more than 200 million years ago. Another example is that when viewed in ultra-violet, clusters of stars can be seen along the arms and in the centre, particularly the hottest, bluest, and youngest stars. While viewed in infrared, the cooler gas shows where the next generation of stars will form.

So what’s so different about GWs? GWs are a completely different kind of phenomenon, providing a unique way of observing the universe. While EMs are the oscillation of electric and magnetic fields, GWs are the oscillation of spacetime itself! They are the literal expansion and contraction of spacetime. The use of this new method may allow us to observe right through the barrier of the CMB and uncover more mysteries of our universe.

Where does this leave us?

Our problem is that we cannot “see” past the CMB with EM. As we learn more and refine our understanding of GWs what then may we find through the wall of the CMB? Will we measure the first ripples of the Big Bang itself, the roar of the hypothesised inflationary period, or will we measure something else entirely? This is truly a new and exciting chapter in astronomy. ▢