This mysterious place
So it’s Saturday night before thanksgiving. Got nothing to do, but I feel like writing - writing alot, so why not do it here? Some of you probably know that I have always been quite interested in astronomy for several years (in fact, I really started to get interested in astronomy back around the age of five when I got some basic book on the moon). Living in the city is great; I’m quite the urban person. Unfortunately, one of the biggest problems about living in a city is light pollution. Sure, we can look up to the sky on a non-cloudy night and see some stars. Of course, this is nothing compared to what you will see, for example, up north in the Muskokas. I have done stargazing a few times in my life, however since I don’t own my own telescope, the best I can do when wanting to looking at the cosmos is either use my naked eye or search for images on the net. Looking at pictures on the internet isn’t nearly the same as if I was actually looking at something with my own eye through a telescope. But looking through a telescope doesn’t always give you everything either, in fact, looking through a telescope shows you very little about what is actually out there. Our eye can only see things that are within our visible spectrum, from reds to purples, but there are many things out there that we cannot just see.
Everyone knows that the universe is a mysteriuos place. We know very little about it, and we aren’t even sure if what we know is really correct. One mystery of the universe is the presence of dark matter and dark energy. Let me say now that I won’t be writing a scientific article here, this is simply for personal interest. Just by reading those words one would naturally get a sence of mystery. To put things very, very simply, dark matter and dark energy cannot be seen, however they make up the vast majority of the universe. Scientists believe that 73% of the universe is made up of dark energy, and 23% is made up of dark matter. To put things into perspective, all normal matter (planets, stars, asteriods, etc) make up only 0.4% of the universe! The remaining 3.6% is made up of interstellar gas. To me it is quite interesting that we cannot visually see about 96% of what is out there. This entry will focus only on dark matter (otherwise it will get way to long), so I’ll explain my views on dark energy in a later entry.
People have asked me before, “if we can’t see dark matter, then how do we know it is there?” Think of a black hole for a moment. Black holes eat up all of the light around them. Their gravity is so strong that even light, travelling at such a speed, cannot escape the hands of the death beacon. Since no light reflects off of black holes, we cannot see them, and we will most likely never see one. We know that black holes are around, however, because of the influence they put on objects that are unfortunate enough to get near to them (such as stars and dust/gas clouds). As this matter from the clouds or stars approach the black hole, they start to accelerate to speeds near the speed of light. Upon doing this, they give of tremendous amounts of energy in the forms of x-rays. We now know how to use these x-ray bursts to find where a black hole is located (radio waves may also be produced). So, although we cannot see black holes, we are pretty sure we know that they exist and where they exist. We can find the presence of dark matter in the exact same way, using a technique called gravitational lensing.
All objects with any sort of mass exert gravity on surrounding things. The more massive the object, the bigger the influence of gravity on other objects. Let’s say we have a cluster of galaxies, 10 Milky Ways for example, all in a relatively small area of space. Now, if we were looking at this cluster of Milky Ways, we would see something strange if there was a galaxy behind. The light being put off from the galaxy behind the cluster would be bent as it travels through this high gravity area of the galaxtic cluster. Think of it like putting a pencil in a glass of water (it looks like it breaks in two). So, the galaxy behind is completely distorted. Here is an example of what gravitational lensing looks like: http://www.windows.ucar.edu/the_universe/images/ab2218_sm.jpg Notice the weird streaks going in a circle around the bright galaxy near the center of the image? Those streaks are a galaxy behind, being completely distored.
We can tell the presence of dark matter in the same way. Dark matter does not interact with light at all. Some scientists believe that light simply goes right through this stuff (some even believe that dark matter is actually stuff caught in a dimension between our universe and another). Dark matter does seem to have a gravitational influence, in fact, it seems to have a very strong gravitational influence, meaning that dark matter must be very massive. The Hubble Telescope recently took a look at one part of the sky, and although it can only see light, it also detected the presence of dark matter through lensing. Here is the official image showing what hubble found (the bright spots are galaxies, whereas the blue globs are dark matter; sure is a lot more stuff out there than what we actually see isn’t there?): http://news.bbc.co.uk/nol/shared/spl/hi/pop_ups/07/sci_nat_enl_1168021092/img/1.jpg
So, is dark matter real? We honestly have no idea. Tests are showing that the stuff does seem to be out there, however, as mentioned earlier, we never know if we are right about anything when talking about our universe. Since we can’t see it, we will probably have a very hard time being 100% sure that it is out there. When it comes to this subject, I cannot offer a good opinion on whether I believe in its presence or not. Sure, the idea looks great, and there is more and more science that is showing that it is probably out there, and in a way I do believe that dark matter fills the universe. I am a strong believer that there are things out there that we simply cannot fully understand. The idea of 23% of the universe being made up of a matter that cannot be sensed in seeminly any single way except through it’s gravity effects on its surrounding stuff (light) is pretty mind boggling (and it gets even more mind boggling when the topic of dark energy comes into play).
If you have an interest in dark matter, or if this blog entry has given you an interest, then simply head over to wikipedia (don’t worry, their article on dark matter is pretty acurate) and read up about it. I hope this entry has not confused you too much, and I also hope you enjoyed reading it. Leave a comment if you wish.
-A Gam
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