Heather Fulton gives the non-nonsense facts behind some of science’s most obscure theories…

Scientists think that they’ve seen evidence for Dark Matter.

Dark Matter is a difficult concept to understand. Many separate discoveries have led scientists to conclude that we can’t actually see all of the matter in the universe. For example, from observing light from other galaxies, we can see that some of their properties require much more mass than can be seen from starlight. Now, even a few of my fellow 4th year physicists are sceptical about this. To them, it seems much more likely that we have our theories about gravity all wrong, rather than having to explain things by a convenient ‘invisible’ form of matter. But, what’s to say that all matter needs to be visible?

When we see objects, it’s because the photons interact with the particles that the object is made of, and the carry the information about the object back to our eyes. But this is not necessary for all particles, and scientists believe that about 90% of the matter in the universe is in the form of this Dark Matter. It is though, by definition, very difficult to observe, and therefore very difficult to prove.

The most promising candidate for the dark matter particle is the charmingly named WIMP – a weakly interacting massive particle. These are very heavy (much heavier than the protons and neutrons we’re made of) and they don’t interact with our normal detectors, making them pretty difficult to spot. Because their signal is so weak, it’s easy to mix them up with other signals found all around us, so scientists have hidden themselves away in an abandoned mine in America to try and block out all the excess noise. There’s actually a team working in an old mine in Yorkshire, 50km south of here who are currently under the impression that they’ve finally been able to observe it, provoking much excitement. Unfortunately, their result doesn’t statistically prove anything, but this is a very promising step so watch this space.

Science explained: Black Holes

A black hole is formed when a massive star dies. The violent explosion turns it into an enormous fireball, leading to an eventual collapse under its own gravity and the production of a black hole. Imagine placing a bowling ball on a thin sheet on rubber – the ball would completely distort the sheet and cause objects nearby to fall into the hole with it. This is what a black hole is like, but with the two-dimensional sheet now three-dimensional space. A tricky concept to get your head around; it’s not easy to think in 4-dimensions…

Black holes are not directly observable (hence the name) but they can be detected by watching the way objects behave around them. For example, the stars at the centre of our galaxy, the Milky Way, are in orbit around something invisible and extremely massive. Scientists have concluded therefore the existence of  a Super Massive Black Hole. It’s nothing to worry about, as long as we stay in orbit around the centre of the galaxy we’re not liable to fall into it.

If you were unlucky enough to fall down a black hole, you wouldn’t be coming out to tell the tale. Once you reached the horizon, you would be pulled and stretched to the point of being unrecognisable. And probably fairly dead. Due to the warped space around the blackhole, to an observer it would look like you never actually got there. As you observe light from closer and closer to a black hole, it is taking longer and longer to travel to you. This means that light from just around the horizon is taking an almost infinite amount of time, and to an observer it would look like you’d slowed down to a stop.

Now, a less known phenomenon is the ‘White Hole’, the opposite of a black hole and, according to some theories, where matter is ejected rather than sucked in. The two could theoretically be joined, passing matter from one end of the universe to the other, making the concept of ‘worm holes’ into more than just science fiction…
Heather Fulton