Dark Energy For That Matter

The fantastic Vera Rubin

Dark Matter and Dark Energy, it's something you'd expect to find in a Stephen King novel, not in main stream physics. But here it is all the same.

As with many things I have a bit of a problem with dark matter, I'm not completely sure it exists, but before we get to that, let's take a little look at the state of play.

Questions: Who dreamed this one up? and why do we even need it?

The first answer is easy, it was first postulated by Fritz Zwicky, which also leads neatly onto the second question, which was also answered by Zwicky.

Zwicky was an astronomer studying the motion of galaxies in 1933. He measured the mass of the galaxies using something called the brightness method. Then he measured the mass of the same galaxy using the orbital method and found that the mass for 400 times larger than the original. This difference is now known as "the missing mass problem" and a problem it is.

Now you may be wondering if one or both of the techniques are at fault, it was a question that first crossed my mind, but there is evidence (that I will put in another post) that while complex they both have merit.

Zwicky said that there must be additional "dark" matter to explain the extra mass and no one took a blind bit of notice of his idea until the 1970s when other problems started to arise.The most famous being that discovered by Vera Rubin. Vera was measuring the predicted angular motion of galaxies and the observed motion of galaxies by galactic rotation curves.

Kepler's laws are beautiful

This is basically measuring the speeds of the stars rotating in a galaxy. The further from the centre the slower they go according to Kepler's laws. Which are amazing by the way (I will do a post on these elsewhere because the really are brilliant). Only this was not observed, the stars were all travelling at pretty much the same speed, irrespective of distance. So, how to explain it? re-enter Zwicky's idea of dark matter.

Now we have a small problem because we can't actually see this stuff and we have not been able to come up with a single experiment to find the missing 90%+ of the universe! So far all we can do is infer its existence from the behaviour of various galaxies and gravitational lensing.

Gravitational lensing happens when light from distant galaxies is bent by the large gravitational fields of black holes (not that I believe the exist, read my post on this when I finish it!) or dark matter.

But is this evidence enough to dream up this exotic matter? Personally I am not sure. I am tempted to look for other explainations. Such as? Well, MOND, Modified Newtonian Dynamics for one. The idea here is that Newton's law of gravitation has only been verified when gravitational acceleration is fairly large. We know that Newton's law breaks down when gravitation forces get really large, maybe ot also fails when gravitational accelerations are very small?

What I also find interesting is that some scientist use the missing mass problem to cast doubts on the Big Bang, which is currently the favourite for the start of everything. Can this be true? Could the Big Bang be wrong? Why not? I certainly have my doubts. But then I doubt just about everything. If dark matter does it exist then it will also raise problems for the Standard model of physics, which cannot currently explain dark matter.

The thing for me though is the idea that 90%+ of the universe may actually be made up of something that we cannot even detect. I wonder if the faster than light neutrinos have got anything to do with dark matter?

I turned on the TV one evening to here a guy describing something that was a total mystery, could not be seen or felt, and yet was believed by many to influence everything in the universe. This unseen force that would have a profound impact on mankind should it ever be shown to be true... I thought to myself, I don't remember reading that there was any programs on about God. It was actually describing dark matter. Or was it?