Although I find that the night sky offers tranquility within the spectacular, thinking about it too much is surreal and dis-orientating. Not the sky of a brightly lit city, but the space we see when remote; that is deeply peppered with the twinkles and winks of thousands of stars. It’s mind boggling to consider that this is the true realm of time travel. Given how long light takes to reach us from these sparkles many of these stars do not live today. All we are seeing is an image of their previous existence from millions of years ago. A Forbes article explained that today if an alien 65 million light years from Earth was to observe our planet — they would survey it as it was in the time of the dinosaurs. Unearthly huh?
As I’ve stared into the abyss above, I have often wondered what is the tangible up-there that I am actually contemplating. These magnificent moments seem to suggest that the universe is full — full of stuff. The Star Wars vision of the sky implying that the universe is a chaotic jumble of rocks, minerals, gases. But hold on. Is it really? I’m now going to grossly over simplify to try to explain where we are in our understanding of the composition of our universe…
Definitions first. When we discuss the universe, it is helpful to know that it is an entity made up of millions of galaxies. Each galaxy is a gravitationally bound system of stars, dust, matter etc. Matter according to the Encyclopaedia Britannica is defined as ‘material substance that constitutes the observable universe and together with energy forms the basis of all objective phenomena’…..hmmm…thats clear. Simply put, matter is some of the ‘stuff’ that makes up our universe.
When the Big Bang happened, the theory goes that all matter in the universe was created. Most matter we think of as atoms formed from a combination of neutrons, protons, electrons and other sub-atomic particles, able to be manipulated into different states (for example into solid, liquid, gas or plasma form). Matter makes up us, rocks, gases, chemicals, commodities, dust — everything we appreciate around us. Initially we thought that was it; we had achieved clarity and hence mastery of the universe. But in the 1930’s inconsistencies arose that troubled this thinking.
Zwicky, a Swiss astronomer suggested that if we added up the matter we could observe across galaxies (from analysing the quantum of matter we believe was emitted at the Big Bang which in itself sounds impossible), there was not enough matter to explain how gravity held everything together. Especially given the speed at which these galaxies were spinning. He suggested that there was something unobservable in the universe, something ‘dark’, that had a strong gravitational pull, keeping planets from pivoting away. But Zwicky wasn’t taken seriously until later work by scientists revealed that stars further away from the sun (which theoretically are exposed to a much weaker gravitational pull from the sun), somehow move just as quickly as those closer. There was a missing component to their thinking.
Scientists started to believe that Zwicky was right. That there is something else that helps to bind the universe together which accounts for the movements of objects we observe in the universe. But here’s the thing — we don’t really know what that is and what it is made of. So for now, we have termed it ‘Dark matter’.
What do we know of Dark matter? The theory says that whatever it is, it does not interact with the electromagnetic force so it does not interact with light — absorbing, emitting or reflecting it and can only be detected by its gravitational effects. Could it be a new particle such as WIMPs — Weakly interacting Massive Particles or a type of gravity if our understanding of gravity is wrong? We don’t know as we have never been able to detect either type even though we have theorised that if it is a particle within a minute 10bn of these will have flowed through your head! Latest theories suggest that Dark matter could be hiding in black holes.
To re-iterate — we have no evidence whatsoever of the existence of Dark matter despite looking for decades. I have heard it described as a concept on the ‘Border of measurable and imagination’ — it is that freakish and defying.
So let’s pull this together to answer our original question. Our rough assumption today is that if you were to break down the composition of the universe it would be c30% matter of which 80% is Dark matter. The remaining 70% of the universe is deemed to be energy which we project is mostly Dark energy. That is — what we observe (baryonic matter) such as the stars, planets, dust etc is only c6% of the whole universe. Only 6%!
I’m conscious I should attempt to explain Dark energy as I have mentioned it. But I can’t. The reason is that it is even more mysterious than Dark matter despite being thought to be more prevalent. It could be a distortion of space time rather than a something. Again we have never ‘detected’ it but our working assumption is that matter tends to pull objects together due to gravitational pull. If that was all there was, then galaxies in the universe should be slowing down and compressing together. Instead we have observed that objects within are accelerating and the universe is expanding — which we have considered is the impact of this Dark energy.
94% of the universe is made up of these dark elements and for decades all we have been able to do is theorise about their existence. Armed with this knowledge, I still find looking into the void breath-taking but now when I ponder too deeply, this ignorance of what is up there is totally confounding and to be honest a little disturbing.
A Man Said to the Universe by Stephen Crane
A man said to the universe:
“Sir, I exist!”
“However,” replied the universe,
“The fact has not created in me
A sense of obligation.”