Cosmology is basically the study of the physical origins of the whole Universe, its evolution, future and fate so it basically has to do with some of the amazing big questions that all of us dare to ask but few of us dare to actually try to understand in a serious way.
As a cosmologist in formation, I want to tell you why Cosmology is incredibly amazing and why we should be encouraged to keep seeking answers for those primordial questions that we have when we were kids such as "Where does everything come from?", "What is the Universe?". In my personal experience, I must say that being a kid who was passionate for physics and space made me very enthusiastic about those questions. When I did my undergraduate education in Astronomy (for five years) those questions became even more interesting and complicated "What is the fate of the Universe if it is expanding?", "Will it expand forever?", "What exactly is the Big Bang?", "What the hell is dark energy?", "What do people even mean by dark matter?", "Does the Universe come from the other side of a black whole that swallowed another Universe?", etc.
Now that I am an astronomer and I have the opportunity to study Cosmology at a first world graduate level, I feel like those questions have become part of my life (not only because I have to do homework assignments, research and exams about them) but because I find them more beautiful and amazing every time I think about them.
To be quite honest, I didn't have a strong background in Cosmology before coming to the Netherlands for my master education, so I pretty much made the decision of studying this specialization for curiosity even though I didn't know nor understand much about it. But today as I write this post, I feel like I have made the right decision because I have always wanted to be part of something great and I think the advances in Cosmology are huge for science and humanity in general. Maybe it is the way to go if I want to accomplish my dream of working with top level scientists around the world in very cool things like understanding what the Universe actually is.
Let me try to quickly convince you about how cool and interesting Cosmology is in the context of our current most accepted model, and why I find a sublime motivation in studying this hard branch of physics and astrophysics. Let's state the basics (with no mathematical or physical details):
The very first step to do Cosmology is trying to understand the first stages or the Universe, so we need to start from the basic and natural question which is "How can we learn about the past of the Universe?". As a very basic and non-precise way to answer this question, we note that because all the astronomical objects we observe are going away from us, we assume that the Universe is expanding, so it must have been smaller in the past; the further we go back in time, the smaller the whole Universe was and at some point in time it must have been infinitely small. That simple view of the evolution of the universe is what we know as Big Bang.
The further we can physically see (with our current technology) in the past is the afterglow of the Big Bang (when the photons were able to decouple from the particles so that they could leave this very dense plasma) that we see as a microwave radiation that we call cosmic microwave background (CMB). This is our most precious relic in cosmology, because it allows us to test our theoretical models of expansion,measure the flatness of the Universe, it sets constraints on our basic assumptions about the first observable emission of photons, etc.
After the decoupling of photons and the expansion of the universe started it is obvious that some structure started forming in the form of galaxy clusters and large scale structure that we observe today, but how did that happen?. The accretion was not simply a gravitational pull caused by ordinary atoms in over dense regions, the story starts to become more complicated because we need to introduce a different form of matter responsible for the formation of structure.
Observations from rotational curves of galaxies show that they rotate faster in their outer parts as it was expected, the clustering of galaxies, gravitational lensing and other observational effects made scientists came up with the idea of the existence of some strange type of matter that doesn't interact electromagnetically so you can only trace its existence by its gravitational effects, they didn't know what it was so they called it Dark Matter (things are getting really strange). This form of matter would be the one that would create the gravitational potential wells that would make ordinary matter (matter that emits light) come together and form galaxies.
Now, our observations show that the Universe expands, but not only that, it expands at an accelerated rate (See a previous post about the accelerated expansion of the Universe: http://bit.ly/2gjdYee) so there had to be an explanation for this to happen. This is when Dark Energy came to the game, but it was not only a small parameter to include in Friedmann equations, it became the dominant component of the Universe, being about 70% of the composition of the Universe (things are getting even worse).
So what is the panorama in Cosmology right now?. Well, in a very simplistic way, we have a theory that says that the Universe started in a "Big Bang", then it continued expanding and dark matter was the responsible for creating the large scale structures we see today, and its expansion has been accelerated for a non-understood dominant component of the Universe that we call Dark Energy. This model is called the Lambda-CDM model.
No matter how beautiful you think this model is, you cannot hide the fact that it has great problems that we need to solve, just to name a few (again with no details) we have:
The flatness problem: The Universe seems to be very flat in our CMB observations but a flat Universe is a very unstable Universe that could not have lasted for so long and it would have had to be extremely flat in a precise way that we don't think should be the reality.
The horizon problem: Some parts of the universe could not have been in casual contact in the past so that they were not able to interact thus becoming homogeneous, but the observed CMB is very homogeneous which suggests that there has to be some mechanism like "Inflation" (a short period of time in which the Universe had an exponential acceleration) to make this problem have a congruent solution.
Dark matter and dark energy: About 95% of our Universe seems to be made of something whose nature we absolutely ignore.
The singularity associated with the Big Bang: Although many cosmologists would say that it is not a problem with the Lambda-CDM model because the model doesn't go that far, it is still a huge problem in all of our current theories of the beginning of the expansion.
So the conclusion is, we don't know much about the Universe!, we are really ignorant in this time of history and there are a lot of questions to be solved, but this is not necessarily a bad thing, because it means that there is a lot of work to do and maybe a huge advance could be nearly at hand, also there is more work for us cosmologists and we can try to really solve the questions that we had as kids and that now have become even more wonderful.
Regarding this idea that a huge advance in cosmology could be at hand, I must mention that a few days ago, an interesting paper by Erik Verlinde, a renown theoretical physicist from the Netherlands was published. In his studies, he attempts to show that the behaviour of astronomical objects related to the existence of dark matter and dark energy could be explained with a different approach in which the properties of the vacuum entropy and the entanglement in quantum scales made space time behave the way it does in those large scales, although his theory has still many flaws, this is just a great example of how interesting this topic really is and how diverse the ideas can be postulated to solve the puzzle.
One of the most encouraging things that I have had lately was a talk by a world wide expert in the field who made me love Cosmology even more. It was Mark Trodden from the University of Pennsylvania who gave us a talk about the work that is currently been developed in the context of these great problems in Cosmology, mostly regarding the use of scalar fields that make space time behave the way it does, it was simply amazing the way he showed to us the work of many great scientists all around the world.
A huge top level bunch of scientists are currently doing their best to help humanity understand this universe where we live. This is why I think it is so important to keep myself motivated with Cosmology because although every day I realise that it is really hard and challenging, I also realise that it is incredibly interesting and that the dream that I have always had about being part of something great can be fulfilled in this beautiful field of science. Maybe I won't be able to help at all in the creation of a nice theory, but that doesn't mean I shouldn't try to do it. In fact, I can have a great time understanding a little bit about the origin and fate of our Universe, that can be a beautiful motivation for a lifetime.
To all my cosmology friends, professors, and future scientists, I hope you keep on working on these questions because we are a small community and humanity is counting on us to make the difference and get every time closer to understand our position in the Universe as thinking beings.
As many of the ideas, concepts and theories were mentioned without any detail, feel free to contact me for more information.
As a cosmologist in formation, I want to tell you why Cosmology is incredibly amazing and why we should be encouraged to keep seeking answers for those primordial questions that we have when we were kids such as "Where does everything come from?", "What is the Universe?". In my personal experience, I must say that being a kid who was passionate for physics and space made me very enthusiastic about those questions. When I did my undergraduate education in Astronomy (for five years) those questions became even more interesting and complicated "What is the fate of the Universe if it is expanding?", "Will it expand forever?", "What exactly is the Big Bang?", "What the hell is dark energy?", "What do people even mean by dark matter?", "Does the Universe come from the other side of a black whole that swallowed another Universe?", etc.Now that I am an astronomer and I have the opportunity to study Cosmology at a first world graduate level, I feel like those questions have become part of my life (not only because I have to do homework assignments, research and exams about them) but because I find them more beautiful and amazing every time I think about them.
To be quite honest, I didn't have a strong background in Cosmology before coming to the Netherlands for my master education, so I pretty much made the decision of studying this specialization for curiosity even though I didn't know nor understand much about it. But today as I write this post, I feel like I have made the right decision because I have always wanted to be part of something great and I think the advances in Cosmology are huge for science and humanity in general. Maybe it is the way to go if I want to accomplish my dream of working with top level scientists around the world in very cool things like understanding what the Universe actually is.
Let me try to quickly convince you about how cool and interesting Cosmology is in the context of our current most accepted model, and why I find a sublime motivation in studying this hard branch of physics and astrophysics. Let's state the basics (with no mathematical or physical details):
The very first step to do Cosmology is trying to understand the first stages or the Universe, so we need to start from the basic and natural question which is "How can we learn about the past of the Universe?". As a very basic and non-precise way to answer this question, we note that because all the astronomical objects we observe are going away from us, we assume that the Universe is expanding, so it must have been smaller in the past; the further we go back in time, the smaller the whole Universe was and at some point in time it must have been infinitely small. That simple view of the evolution of the universe is what we know as Big Bang.
The further we can physically see (with our current technology) in the past is the afterglow of the Big Bang (when the photons were able to decouple from the particles so that they could leave this very dense plasma) that we see as a microwave radiation that we call cosmic microwave background (CMB). This is our most precious relic in cosmology, because it allows us to test our theoretical models of expansion,measure the flatness of the Universe, it sets constraints on our basic assumptions about the first observable emission of photons, etc.
The Cosmic microwave background as mapped by Planck (with corrections and modifications).
After the decoupling of photons and the expansion of the universe started it is obvious that some structure started forming in the form of galaxy clusters and large scale structure that we observe today, but how did that happen?. The accretion was not simply a gravitational pull caused by ordinary atoms in over dense regions, the story starts to become more complicated because we need to introduce a different form of matter responsible for the formation of structure.
Observations from rotational curves of galaxies show that they rotate faster in their outer parts as it was expected, the clustering of galaxies, gravitational lensing and other observational effects made scientists came up with the idea of the existence of some strange type of matter that doesn't interact electromagnetically so you can only trace its existence by its gravitational effects, they didn't know what it was so they called it Dark Matter (things are getting really strange). This form of matter would be the one that would create the gravitational potential wells that would make ordinary matter (matter that emits light) come together and form galaxies.
We don't know what dark matter is, but we think that it must be
there given its gravitational effects.
Now, our observations show that the Universe expands, but not only that, it expands at an accelerated rate (See a previous post about the accelerated expansion of the Universe: http://bit.ly/2gjdYee) so there had to be an explanation for this to happen. This is when Dark Energy came to the game, but it was not only a small parameter to include in Friedmann equations, it became the dominant component of the Universe, being about 70% of the composition of the Universe (things are getting even worse).
So what is the panorama in Cosmology right now?. Well, in a very simplistic way, we have a theory that says that the Universe started in a "Big Bang", then it continued expanding and dark matter was the responsible for creating the large scale structures we see today, and its expansion has been accelerated for a non-understood dominant component of the Universe that we call Dark Energy. This model is called the Lambda-CDM model.
No matter how beautiful you think this model is, you cannot hide the fact that it has great problems that we need to solve, just to name a few (again with no details) we have:
The flatness problem: The Universe seems to be very flat in our CMB observations but a flat Universe is a very unstable Universe that could not have lasted for so long and it would have had to be extremely flat in a precise way that we don't think should be the reality.
Small variations on the flatness of the Universe in the early Universe would result in very
different fates for the Universe.
The horizon problem: Some parts of the universe could not have been in casual contact in the past so that they were not able to interact thus becoming homogeneous, but the observed CMB is very homogeneous which suggests that there has to be some mechanism like "Inflation" (a short period of time in which the Universe had an exponential acceleration) to make this problem have a congruent solution.
Components of the Universe in the Lambda-CDM model.
The singularity associated with the Big Bang: Although many cosmologists would say that it is not a problem with the Lambda-CDM model because the model doesn't go that far, it is still a huge problem in all of our current theories of the beginning of the expansion.
So the conclusion is, we don't know much about the Universe!, we are really ignorant in this time of history and there are a lot of questions to be solved, but this is not necessarily a bad thing, because it means that there is a lot of work to do and maybe a huge advance could be nearly at hand, also there is more work for us cosmologists and we can try to really solve the questions that we had as kids and that now have become even more wonderful.
Regarding this idea that a huge advance in cosmology could be at hand, I must mention that a few days ago, an interesting paper by Erik Verlinde, a renown theoretical physicist from the Netherlands was published. In his studies, he attempts to show that the behaviour of astronomical objects related to the existence of dark matter and dark energy could be explained with a different approach in which the properties of the vacuum entropy and the entanglement in quantum scales made space time behave the way it does in those large scales, although his theory has still many flaws, this is just a great example of how interesting this topic really is and how diverse the ideas can be postulated to solve the puzzle.
One of the most encouraging things that I have had lately was a talk by a world wide expert in the field who made me love Cosmology even more. It was Mark Trodden from the University of Pennsylvania who gave us a talk about the work that is currently been developed in the context of these great problems in Cosmology, mostly regarding the use of scalar fields that make space time behave the way it does, it was simply amazing the way he showed to us the work of many great scientists all around the world.
A huge top level bunch of scientists are currently doing their best to help humanity understand this universe where we live. This is why I think it is so important to keep myself motivated with Cosmology because although every day I realise that it is really hard and challenging, I also realise that it is incredibly interesting and that the dream that I have always had about being part of something great can be fulfilled in this beautiful field of science. Maybe I won't be able to help at all in the creation of a nice theory, but that doesn't mean I shouldn't try to do it. In fact, I can have a great time understanding a little bit about the origin and fate of our Universe, that can be a beautiful motivation for a lifetime.
To all my cosmology friends, professors, and future scientists, I hope you keep on working on these questions because we are a small community and humanity is counting on us to make the difference and get every time closer to understand our position in the Universe as thinking beings.
The beauty of understanding the Universe.
As many of the ideas, concepts and theories were mentioned without any detail, feel free to contact me for more information.
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