The dark side

I’m sure you remember the deep thoughts on known and unknowns by a certain Donald Rumsfeld. Ridiculed by many, hailed as profound wisdom by a few, these words fit our current understanding of the Universe remarkably well.

Maybe you have thought about this already? If not, consider this: According to increasingly precise observations, most recently from the Planck Satellite, the Universe had three main components;

First we have the known knowns, the normal matter. The stuff that we are all made of, the stars in the sky and so on. Basically, things that physicists would claim to understand.

Sadly this is only a measly few percent of everything,

The second part is the dark matter. The known unknown. Needed to explain how galaxies form and why stars in the outer edges of individual galaxies move as they do. A typical physicist would not claim to know precisely what this stuff is, but he/she might be prepared to make suggestions. This fifth of the Universe is mysterious, but maybe not outrageously so.

Finally, we have the third part, the unknown unknown. The dark energy. Sounds a bit sinister, doesn’t it? And it is. Nobody seems to have a working explanation for this part. Yet we need it to explain why the rate of expansion of the Universe is gradually increasing. And it makes up pretty much three quarters of the Universe as well. So, whatever it is... there’s “lots” of “it”.

Whenever you have unknowns like this in science you find speculation galore. You could argue that this is healthy and may in the fullness of time lead to progress on problems we don’t currently understand. Alternatively, you could take it as evidence that some scientists are ultimately loons. I think the truth lies somewhere in between these extremes. Hopefully closer to the former, but I wouldn’t bet on it.

I am not a great fan of dark energy. It is too freaky.

I can cope with the idea of dark matter, though. I even find some suggestions amusing.

A recent idea about the known unknown provides particular pause for thought. It is really quite simple. Basically, all the stuff that we see and understand interacts electromagnetically (emits light, essentially). The dark matter does not. Obviously. It is dark. It only affects gravity. So... the new suggestion is that dark matter could be pretty much “normal” stuff, only not interacting through standard electromagnetism. There could be dark atoms, molecules, larger nuggets and so on. Perhaps dark stars, planets... Maybe dark matter people, or is that going a bit far? Anyway, the point is that we would never know, as we wouldn’t see these things.

In order to build large dark objects there would have to be some force to replace electromagnetism. A dark force, as it were.

Does this sound a bit too much Star Wars for your liking? Perhaps, but ... and this is a big but... the idea was proposed by well-known scientists at some of the world’s best Universities. Whether this is the result of inspired thinking or too much science fiction, well... hopefully we will find out. One day.