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| Sunday, 13 February 2005 |
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Junior Observer |  |
| News Business Features Editorial
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Cosmic mysteries Although we have heard so much about the Solar System there are thousands of mysteries that lie outside the boundaries of our tiny Solar System. Deep Space remains an incredible puzzle yet to be explored. Let's look at some of these interesting things in space... Black holes
Black holes were once thought to be the monsters of the Universe. But now astronomers think that rather than being a space menace, black holes may be fundamental to the creation of galaxies. Black holes are regions of space where gravity is so strong that not even light can escape, making them impossible to see. But we can see the stuff that is being sucked into these massive cosmic vacuum cleaners. Anything that approaches a black hole is first torn apart by its huge gravitational force and then formed into a flat rotating disc that spirals into the hole. As this debris gets closer and closer to the mouth of the black hole, it speeds up and the tiny bits start to smash together. The material heats up due to this friction [this is the same effect as when you rub your hands together to warm them up]. When this happens around a black hole, X-rays are given off which we can detect. If the black hole is really large and has lots of debris in its disc, then it can reveal itself as one of the brightest objects in the Universe - a quasar. There are two main types of black holes - stellar and supermassive. Stellar sized black holes are the remnants of massive dead stars that have imploded. The nearest one to us is part of a binary system called Cygnus X-1, discovered in 1971. It is in the constellation of Cygnus, also known as the Northern Cross. It's estimated that our galaxy contains millions of these stellar black holes. Supermassive black holes, on the other hand, can have initial masses millions of times the Sun.
It's now thought that they may lurk in the centre of every galaxy and be integral to the way galaxies evolve. There might also be other types of black holes, such as mini black holes, smaller (in volume) than atoms, but as massive (in amount of matter) as whole mountains. Or even middle-sized black holes, mid-way between the stellar and supermassive variety. It's possible that there could be such things as 'white holes', the opposite of black holes, spewing out matter and energy into the Universe. However, this is just another of the cosmic mysteries still awaiting a solution. Wormholes As any science fiction fan knows, one of the most menacing and mysterious things in space is a wormhole. Wormholes are a possible consequence of Einstein's Theory of General Relativity. Einstein came up with the remarkable idea that mass warps space, and the bigger the mass, the more space will be bent. This strange theory was proved by Arthur Eddington in 1919, when he journeyed to the Amazon forest for the solar eclipse and proved that the Moon sent light from the Sun as it crossed in front. Theoretically, a wormhole could be formed when two or more massive bodies warp space and the fabric of space collides, forming a tunnel between distant places. The easiest way to think about this is in two dimensions rather than three. Think of space as a piece of paper, which is bent over on itself. If a weight is put on top of the paper it will sag towards the centre. If there was another weight on the opposite side, then it would also sag towards the centre, if they eventually met, then a wormhole would form, joining the two regions.
Although being sucked through the fabric of space does seem pretty menacing, wormholes would offer amazing possibilities to travel through space and time. Popping through a wormhole could bring distant galaxies to your doorstep. What's more, by doing this you are effectively travelling faster than the speed of light, and so by passing through a wormhole and back you could travel into the future. No one knows whether wormholes exist let alone what would happen if you sent a spacecraft through them. If they do exist they could be very short-lived, and may not even survive long enough for a spacecraft to reach the other side. And if the spaceship did make it, its mass might cause the wormhole to snap shut, cutting the astronauts off for good. Dark matter One of the biggest mysteries in modern astronomy is the fact that over 90 per cent of the Universe is invisible. This mysterious missing stuff is known as 'dark matter'. The problem started when astronomers tried to weigh galaxies. There are two methods of doing this. Firstly, we can tell how much a galaxy weighs just by looking at how bright it is and then converting this into mass. The second way is to look at the way stars move. Everything in the Universe rotates. The Earth spins on its axis. The whole planet orbits around our parent star, the Sun. The Sun rotates around the centre of the Milky Way, along with the billions of other stars in the Galaxy, forming a huge cosmic dance. This rotation provides another way of weighing a galaxy. Studying how fast stars at the very edge move, reveals the mass of the whole galaxy. The faster the Galaxy rotates, the more mass there is inside it. But when astronomers such as Jan Oort and Fritz Zwicky did the two sets of sums in the early 1930s they came upon a big problem. For every galaxy they studied, the two answers didn't match. They were very confident that both methods were sound as they'd been tried and tested for many years. So they came to a startling conclusion - there must be stuff out there that we just can't see - and so they called it 'dark matter'. This dark matter was really important, as if it wasn't there, then galaxies would fly apart as they spun round. This might seem like a strange conclusion, but it's not really that bizarre. Imagine looking at a tower block at night. Although you can only see lights coming from some of the rooms, that doesn't mean that there aren't any more rooms in the tower. Just like these unlit rooms, dark matter can't be seen, because it doesn't shine. Astronomers are currently hunting for this missing matter. It may consist of lots of strange sounding things like MACHOs, WIMPs and neutrinos. Or there may be new solutions involving dark energy or superstring theory. But whatever it is, finding it will help to answer one of the most fundamental questions in astronomy - what is the fate of the Universe? Courtesy: BBC |
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