Re: Two questions about Astronomy.

Hi Gemma,

1) What is Dark Matter? You have just asked one of the fundamental questions in astronomy! No-one really knows what dark matter is. We believe it exists, because without it a lot of the observations we have made would be inexplicable. A satellite named COBE (COsmic Background Explorer) looked at the background radiation right across the universe and found that it was almost exactly the same everywhere it looked, to within one part in 100,000. What COBE saw was essentially the remnants of the big bang. By looking at the map COBE created, astronomers have worked out that the universe is very probably flat. This refers to the geometry of the universe, which is a whole other topic, and requires some complicated maths and some mind-bending ideas. However, in order for the universe to be flat, it needs to contain a certain amount of mass. The amount of matter we can see only accounts for a very small amount of this mass, so the rest must be dark matter, ie matter we can't see. Nobody really knows what it is, but there are several theories. Dark matter could consist of lots of fundamental particles, distributed throughout the universe, or perhaps in some type of compact astrophysical object formed from many particles. Theories range from the pedestrian to the extreme, but in all honesty, no-one knows what dark matter is, and nor are they likely to in the near future. If you want to delve deeper into this subject, a good starting book is "An introduction to Modern Cosmology" by Andrew Liddle, published by Wiley, ISBN 0471987581. Other non-technical books that might be of interest are "The origin of the Universe" by J D Barrow, and "Before the Beginning" by Martin Rees.

[Moderator's Note: Very recent evidence, from observations of supernovae, indicate that about 70% of the energy that makes the universe flat is actually "dark energy." This is different than dark matter (which constitutes about 25% of the total energy in the universe, the other 5% being the matter we can see), and is even more mysterious!]

2)When you say you want to get into astronomy seriously, what exactly do you mean? In essence, astronomy is physics, and there is no escaping that, but there are ways to avoid the more boring bits of physics. To start with, you could keep astronomy as hobby. Amateur astronomers do a lot of real work, without having to get into all the physics. The best place to start is with your local Astronomy Society. You should be able to find details of your local one, either in your library, or maybe in the back of magazines such as Astronomy Now, a good British publication that lists local astronomy events in the back pages.

If you want to get a bit more serious, it is possible to do Astronomy GCSE. If you have a good science department at school you may be able to persuade them to teach you, though in the current climate this is unlikely. But, as astronomy is a branch of physics, Astronomy GCSE does contain some physics, and is probably much easier to do in the sixth form, after having done your maths and physics (or science) GCSE's. The course is offered by what was the ULEAC exam board, but I think it is now called Edexcel. If you go to their web page www.edexcel.org.uk you can download the details. If you cannot convince your school to teach you, you could try local colleges, who may offer it as an evening course, though this may be expensive. A third option is by correspondence course, though you will need large amounts of self discipline to do it this way! If you write to Edexcel they may be able to give you details of colleges offering a correspondence course.

If you really want to do astronomy, as a career, then you will have to do physics. Many universities offer Physics with Astronomy, and some even offer just Astronomy, such as UCL, but they do have a heavy emphasis on physics, and will require good grades in Maths and Physics A-levels. They do tend to avoid to duller bits of physics though, and just concentrate on the bits you need. Alternatively you could do a chemistry degree (which may well require physics A-level as well), and look at PhD's in Astrochemistry. Many university astronomy or astrophysics groups will have an astrochemistry group. Birmingham, UMIST, UCL and Aberdeen all have strong astrochemistry research departments.

In short, it is hard to do serious astronomy without doing physics, as astronomy is physics, but you can get into various different levels of astronomy. You may find, however, that you start to enjoy physics more, as you apply it to things you find interesting. Physics at university level is very different to school physics, and courses are fairly flexible these days, letting you get what you want out of the course. I hope this helps, and please don't turn your back on Physics.

Sarah