Cities gather us in different ways, we dwell them, walk around its streets and avenues attending our own eagerness. Many cities have rise over us with huge buildings that show the ability of societies to overcome our scale, and so in a display of phenomenal energy, cities keep moving.
Now days, electric light seems to be a primary need for todays society. Cities and their lights shine over the night sky, blinding our eyes of the ordinary exercise of looking to the starry night that practice our ancestors. Those who have been in the Atacama Desert know that once is late night, looking at the stars there is a different experience, from the one we are used to when we look at the stars from our “shining” cities. This thought becomes most significant while we start to think about our everyday experience. Have we lost something in the way?
Our culture as human beings, have always been related to the night sky observation. Today, new planetary systems are discovered weekly, observation tools and instruments are increasingly sophisticated; we can look at the origin of the Universe and make an image of it. We live in a fast and fascinating era in which we can dazzle with images of supernova’s explosions, nebula clouds and faraway galaxies. The understanding of what “surround us” changes radically and Astronomy raises new questions, challenging the limits of our comprehension. Now we can look farther and farther and so wider the horizon becomes.
Facing this prospect, we propose to add different points of view. Contributing to the astronomical reflection from different angles, being the scientific perspective one in many others possible. Because we are interested in poetry, music, art and design, also in casual conversation, laughter, awkwardness and contradictions, in things that move and those who stay quiet, we are interested in large and small questions of humanity.
This first edition of Galatic Magazine is the number cero and has as main subject the Birth, the origin of things and also the origin of this project. This is a starting point of a conversation that we hope will spread in time, and so will convene many voices and many views.
Must of us have seen the stars in a dark night. Chile is situated in a privileged geographic place to look to the inner parts of our galaxy, the Milky Way. This is a spiral galaxy, with between 100 000 and 120 000 light years of diameter and around 100 to 400 billion and stars and planets in it. We call galaxy to the group of many stars, interstellar dust, gas and particles bound together by gravity. Our Solar System lives in one of our Galaxy’s spiral arms, at around 27 000 light years from the galactic centre.
Now we know what the galaxies are made of, but how were they formed? Until now, we know that gravity is a force (described by Isaac Newton, after looking an a apple falling down a three back in xvii) that makes planets, stars and galaxies to feel attracted to each other and rotate around them. This is the same force that keep us on the Earth, same that makes the Moon rotate around it, and, same as the black hole in the middle of our galaxy that makes billions of stars and planets to rotate around it.
Thanks to contemporary astronomy, now we know that after the Big Bang, some 13 thousand million years ago, gravity generated inhomogenities in the density of the Universe, this means that some regions were more dense than others. These denser regions evolved to form dark matter clouds, that grew to form even more dense clouds. After thousands of millions of years these clouds started to look like what we observed now, huge halos with sizes of a hundred million light years and with masses of about a thousand billion solar masses.
Inside this gigantic halos we find the ordinary matter, that we all know, the one that built up the galaxies, stars, planets and even ourselves. The dark matter halos are very important for the formation of the galaxies, cause even that is matter that we cannot observe, it interacts gravitationally with the ordinary matter helping the galaxies to stay gravitationally bounded.
When the first galaxies originated, the Universe was made of hydrogen, helium and dark matter only. In these early stages of the evolution of the cosmos, many violent events happened that made the galaxies evolved very quickly.
We know now that there are many different types of galaxies, but the main ones are the spirals and ellipticals. The spirals are somewhat younger, they interact with each other and consume all their gas till they end up like ellipticals. Elliptical galaxies have a lot of old stars, due to the lack of gas, without gas they cannot form new stars.
Maybe at this point you are wondering what is dark matter? To answer this question, we are going to explain the most important components of our Universe.
According to the latest observations made with the Plank satellite, the Universe is made of 68,3% of dark energy, 26,8% of dark matter, and, 4,9% of ordinary matter; the matter that all the stars, planets and us are made of.
Dark energy acts exactly opposite to gravity, creating an accelerated expansion of the space-time between galaxies. Dark energy was discovered recently, when Saul Perlmutter (U. of California, Berkeley), Brian P. Schmidt (U. National of Australia), and Adam G. Riess (U. Johns Hopkins) observed a certain type of supernova in near and far galaxies. The astronomers saw that the far galaxies where further than what they predicted them to be. This anomaly was explained by the use of a force that will make the galaxies to get further and further. The further the galaxy is the faster it will move away from us. This discovery gave them the Nobel Prize in Physics in 2011.
The second most important element in the Universe is dark matter, is called dark cause does not emits light, unlike stars, but it interacts with ordinary matter by gravity. Dark matter is super important, is the first seed that will attract the ordinary matter together forming stars, planets, globular clusters, galaxies, clusters of galaxies.
An example I use to illustrate the Universe components is the following; lets imagine we live in a mansion, where the garage is about 6 m long, this is our Universe.
Inside like everyone else, we have the Lamborghini Aventador lp700-4 with a 4.8 m size, this will represent the dark energy. Now inside the car, there’s a 12 years old kid, with around 1.4 m of hight, this is the dark matter. Finally the ordinary matter (what we are made of) would be one of the front lights of the car, of about 25 cm of size.
This analogy shows how little we know and can see from the Universe, but also tell us how far astronomy has gone. Using only this tiny signal from the light of one front bulb, astronomers have been able to tell the brand of the car, the model, how many miles has been running for, and part of its fabrication process. We are still very far from understanding everything, but every time we have better instruments and with them better knowledge comes.
Today we know that dark energy makes that galaxies move away from each other, while gravity does the opposite. The closest spiral galaxy to the Milky Way is Andromeda, both galaxies are close enough so that gravity can win against dark energy, provoking their interaction.In about 3 thousand million years, gravity will make them collide, this happens all the time all around the Universe. After both galaxies merge there will be a fast formation of stars, that will use the remaining gas, till they end up forming an elliptical galaxy.
In theory dark energy is a force a lot stronger than gravity, but only at huge scales. For astronomical objects that are close enough, like planets around stars, globular clusters or galaxy clusters, gravity wins over dark energy. At least this is what we know till now.