Astronomy and its ultimate question 3-SBI Mankind has always been fascinated by the sky wondering what those little dots of light were and whether the sky was as big as we could see. The first one to take a look at the sky through a telescope was Galileo Galilei and he discovered that Jupiter, the biggest planet in our solar system, had moons just like our moon. He even named the first four moons, which are now known as the Galilean moons. At first we thought that the stars were fixed in a solid shell around our solar system but we realised that this was not true. We realised this because we found out that the sun was in fact a star like the little dot of light we saw in de sky at night and thus we found out that our solar system is a part of something much larger, a galaxy, which was called the Milky Way. This meant that the universe was much larger than we initially thought. After this discovery the mapping of the universe began and we started to name stars and placed these stars within constellations. Edwin Hubble was a great astronomer and his discoveries changed our view of the universe. He discovered that nebulas, of which was thought to be part of the Milky Way, were in fact galaxies of their own. There are three different kinds of galaxies; these are spiral galaxies, elliptical galaxies and irregular galaxies. Hubble's theory was that the elliptical galaxies eventually evolved into spiral galaxies. Recently astronomers think there is another explanation. They think that elliptical galaxies are the result of collisions between two or more galaxies. There is an elliptical galaxy in the Virgo cluster that is so big that it consumes every galaxy that comes near. The Milky Way is a spiral galaxy. The closest galaxy to the Milky Way is Andromeda and since this is also a spiral galaxy we could learn much of our own galaxy by looking at Andromeda because this galaxy could be seen from an outside point of view. We are situated within the Milky Way and because of this it is difficult to look at it properly. Hubble made a catalogue of all the galaxies he could see and noticed something strange when he looked at the spectra's of these galaxies. He noticed a redshift in the colour of the galaxies and discovered that the cause this redshift was that the galaxies are moving away from the Milky Way. Looking closer at these redshifts he observed that when the distance between a galaxy and the Milky Way became larger the velocity in which the galaxy was moving away from the Milky Way became higher as well. He concluded that this could only be possible if the universe was expanding increasingly. How this could be was a big mystery. Astronomers recently noticed something strange about the Milky Way when they were measuring the rotation velocity of the stars in the Milky Way around the galactic centre. Astronomers assumed that the velocity of the stars near the galactic centre would much larger than the stars at the edge of the Milky Way. This was true indeed but the velocity of the stars at the edge of the Milky Way was much larger than it should be. Astronomers could think of only one explanation, which is that there was much more mass present in the Milky Way than we could see and since this mass could not be seen they called it dark matter. The discovery of dark matter caused a shift in the astronomy and made astronomers think of the expansion of the universe. At first the expanding of the universe was thought to be the result of the big bang but this does not explain why the universe is expanding increasingly. This raises a question; what if a force exists that we cannot detect that causes the increasing expanding of the universe? This force was called dark energy and with this idea a Nobel Prize in Physics was won in 2011. Although there are so many mysteries in astronomy the biggest question remains; how did it all began? There are several theories for the beginning of the universe. The most common and accepted theory is the big bang theory. According to this theory the universe began extremely dense and hot which expanded rapidly. This expansion caused the universe to cool down to its present temperature. Another theory is M-theory this theory explains that our universe is not the only universe and describes that there is a dimension with several membranes in it. These membranes lie parallel to each other and on every membrane lays a universe. One of these universes is our own universe. The distance between these membranes is extremely small but still we are unaware of the universes on the other membranes. Sometimes these membranes collide with each other and when this happens a big bang occurs. Neil Turok and Paul Steinhardt (2007) had another theory, which is that the universe resets itself. This means that there has been a universe before the one we are in now and this cycle repeats itself. At a certain time the universe collapses and a new big bang occurs and then it starts all over again. This theory is called the ekpyrotic scenario. Turok and Steinhardt were convinced that cycle starts over because of the collision between different membranes. In other words, they also believed in the M-theory and combined it with the ekpyrotic scenario. Although there are many theories about the how the universe began, astronomers still do not know which one is the correct theory. There is a way to find out what happened during the big bang and this is simply to look at the sky. When we look at other galaxies in the universe that are several light-years away from Earth it means that the light we see has travelled several years to reach Earth. This means that the light we see makes an image that originates several years ago and then we would be looking back in time. If we would look far enough into the universe we should be able to see how it began. This sounds easy but it is not since a very sensitive telescope is needed that can look far enough into the universe. If a telescope like that is available a problem rises; at the beginning there were no stars at the beginning of the universe. This does not mean that there is no light at beginning; because the universe was extremely hot at the beginning it would have been emitting light. This light would not be very helpful since at the beginning the universe consisted of separate particles that would eventually form stars and galaxies. This means that the universe would look like a big cloud of light and it would not be transparent. Because astronomers cannot agree which theory correctly describes the beginning of the universe they are now searching for the last piece of the puzzle that could eventually explain how the universe works and thus how the universe began. This last piece of the puzzle is also known as the Higgs particle. In the media it is also known as the God particle. This particle is an extremely small particle and is responsible for a field, the Higgs field, which causes all other particles to experience mass. This field exist throughout the entire universe. A simple way to explain how this field works is that a ball of wool has much more trouble rolling over a wooden table that a ball of steel. In other words, some particles have more trouble moving through the Higgs field than other particles. In order to find out if this is true the Higgs particle first has to be found. The reason why it is so important to find the Higgs particle and thus explain how particles can experience mass is because it can explain how the universe is build up. There are two kinds of particles fermions and bosons; fermions are the building blocks for atoms and bosons are particles that are responsible for forces. All of the bosons are accounted for except the one that is responsible for the fact that all particle experience mass. Thus, if the Higgs particle can be found then all of the building blocks, which the universe consists of, are accounted for and when all the building blocks are known it is much easier to find out how the universe began. Although this sounds easy the search for the Higgs particle has been very difficult. Astronomers have built a Large Hardon Collider (LHC) in Genève, which is a very big particle accelerator. In the LHC particles are accelerated to extremely high speeds and then collide with each other in order to create particles that are very hard to find. Almost all of the characteristics of the Higgs particle are known except how heavy it is but it has to be heavy. This means it is still hard tell if the particle that has been found is a Higgs particle or not.1 On the July 4th 2012 astronomers believed they had found the Higgs particle in one of the experiments at the Large Hardon Collider. The whole world celebrated and it seemed that we were closer to find out how the universe began than we had ever been before. After a few days of research it became clear that this particle was not the Higgs particle but was a particle that resembled the Higgs particle very much. This raised a question; could it be that there are different kinds of Higgs particles and not just one kind? To add more confusion; a new theory appeared which claimed that it could also be possible that the Higgs particle has a very low mass instead of a high mass. This theory is called supersymmetry.2 Answering the question of how the universe began is extremely difficult; astronomers have been searching for the answer for years now. They have tried to look back in time with very sensitive telescopes and they have formed all kinds of different theories but all of these theories could not be proved to be right. They thought they were very close when they began the search for the Higgs particle but when they found a particle that resembled the Higgs particle very much it raised more questions than it answered. As a final blow a new theory appeared claiming that the Higgs particle could also have a low mass instead of a high mass. Ultimately, it is clear that there is still no answer to the question of how the universe began. Naturally astronomers will continue to search for the answer to this question and maybe they find the answer sooner than expected. 1 Schilling, G, Higgs het elementair abc van een elementair deeltje, 2012, Fontaine Uitgevers. 2 Schilling, G, Higgs het elementair abc van een elementair deeltje, 2012, Fontaine Uitgevers.