FeaturesDark does matter

Dark does matter

When the laws of nature appear to be almost as abstract and as illogical as the idea of an omnipotent, omnipresent being creating the universe in 6 days and science fiction seems like a sunday school picnic you realise we’ve come an awful long way in understanding how stuff works. Either that or somewhere along the road to enlightenment we’ve taken a wrong turn or two – which is highly likely, we don’t yet know and quite possibly never will.

As  Arthur C Clarke put it, ‘Any sufficiently advanced technology is indistinguishable from magic’ or put another way, any ideas sufficiently advanced may look like God. We live in very interesting times.

Most of us, I suspect, go about thinking that man has it pretty much sussed, that we understand nearly everything, that science is nearing something of a zenith and it won’t be long before we know it all. It may sound perverse but I find it somewhat comforting that time and again, just as we make some major breakthroughs in our understanding of the way the universe works, nature turns out to be a whole lot weirder than any science fiction writer could have ever suspected. That’s exciting don’t you think?

Everything you’ve ever learned or thought you knew about what ‘stuff’ is, what it’s made of, what the universe is made of, is very possibly wrong. At school we’re taught that the basic unit of matter is the atom, that everything we see around us is made up of atoms and yet it would seem that the mass we can actually detect or interact with only represents a paltry 4% of the mass the universe appears to contain! How is this so, how do we know this?

Only since 1920 have we known that there exist other galaxies apart from our own Milky Way and when Edwin Hubble realised that some smudges of light weren’t gas clouds as previously suspected, but actually other galaxies each containing billions of suns, astronomers set about measuring them and trying to work out how far away they were, how fast they were moving and other vital statistics. Shortly after that scientists noticed things weren’t as they seemed.

Newton discovered then Einstein refined, formulae involving gravity, mass and space which described the motion of bodies, giving us an accurate way to predict the orbits of planets around suns and how anything with mass is affected by anything else with mass. With these powerful tools astronomers observed the motion of stars orbiting the center of galaxies and noticed behaviour that didn’t quite fit. According to these laws of motion the stars on the outer most of a galaxy should be moving slower than those closer to the center, but observations contradict this. Astronomers were startled to find that actually the speed of all stars orbiting a galactic center was pretty much constant. Furthermore, clusters of galaxies orbiting around each other also flouted these laws, suggesting there was much more mass within these clusters than we could see – 10 times more! What was causing it? The answer, for now at least, is so called ‘Dark Matter’. This stuff, if it exists, (and these theories suggest we scrap our preconceived ideas of what  to ‘exist’ actually means) has lots of mass but doesn’t interact with light, it doesn’t reflect light, it doesn’t absorb light, it doesn’t interact with anything, it passes straight through ‘normal’ matter and as yet, has not been detected directly. All we can see are the ghostly affects of its mass on other bodies. Its very much there in one sense but in another its not there at all.

One of Einsteins greatest leaps of original thought was to realise that gravity is the effect of mass on space time, that is to say, anything with mass puts a dent in space time (space time is a hard to imagine concept whereby space and time are inextricably linked – you can’t have one without the other so the two are intertwined creating a kind of ‘fabric’ – its useful to imagine a rubber sheet, any weight such as a snooker ball place on the sheet will deflect any object rolling across that sheet) and anything passing by will feel the effect of that ‘dent’. Gravity even effects light and enough of it will bend light much like a lens does. This ‘lensing‘ effect can be directly observed but again the effect seen and tested in many different areas of the cosmos is way more than expected – ten times more. Theres not enough room here to go into how we know this but this is what Google’s for right?

It is now believed that all galaxies are surrounded by a sphere of Dark Matter which causes this exaggerated lensing effect and helps to hold the myriad of stars in place, affecting a constant procession around the galactic centre. How the physics of Dark Matter exactly work is as yet unknown, the science is brand spanking new. According to observations though, the total mass of the universe is 4% ‘normal’ matter, 27% Dark Matter – so what about the remaining 70%? Well this is stranger and more fantastical still.

Everything you’ve ever learned or thought you knew about what ‘stuff’ is, what it’s made of, what the universe is made of, is very possibly wrong.

Galaxies and clusters of galaxies are not spread evenly throughout the universe. If you’ve attended my lecture on Chaos Theory you may remember a poignant fact – that nature doesn’t favour homogeneity. That is to say, the world around us is all patterns and lumps and clumps. Almost nothing is completely flat and plain. The same is true at ALL scales, even cosmological and if one maps the distribution of ‘normal’ matter in the known universe a wondrous network resembling a sponge or loofa is clear to see. Dark Energy is thought to be the culprit for this structure at the cosmological scale and the remaining 70% of the mass of the universe. Dark Energy acts in opposition to gravity – pushing everything apart. Absolutely nothing is yet known about Dark Energy but perhaps it can be imagined as like the energy of a vacuum? Gravity has a pull on objects proportional to the distance  between them but weirdly, Dark Energy does the opposite – the more distance between massive objects such as galaxies the greater the effect, meaning that the universe is expanding at an ever greater speed in all directions. Imagine drawing spots on a balloon and then inflating it, every spot is moving away from every other spot, there is no centre, the space in between the dots just gets larger.

To say the universe is very large is absurdly understating it, however I’m running out of space here and must wrap it up. For me the fascinating thing about science and the mission to understand the world around us is that ‘fact’ is a transient, illusory thing, ever changing and open to great leaps of imagining, far weirder than any sci-fi novel and far more exciting and liberating than dogma. Keep your minds open people, reality is not as it seems!


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