The Big Bang: just a theory?

Jerliz M Velez Morales

Since I was little I have been hearing about a great theory, the Big Bang theory, but never took the time to go deeper into it. When I go outside at night, I stare at the sky and wonder how the universe was created, what could have made such a complex get beautiful thing. Religiously speaking the universe was created by a superior force, God, and that’s what they have been teaching us since little. I am a christian and therefore I believe in God, but as a student that have been studying physics, I think this theory makes a lot of sense and gives me a more believable answer to many of my questions. The Big Bang theory is an effort to explain what happened at the very beginning of our universe, during and after that moment. The origin of the Big Bang theory can be credited to Edwin Hubble, who made the observation that the universe was continuously expanding. This theory is supported by a number of important observations such as: The expansion of the universe, the abundance of the light elements H, He, Li and the cosmic microwave background (CMB) radiation. According to the theory, the universe used to be a very dense and hot place, but through the years it has come to be less hot. How is that possible? Well the Big Bang theory is a great way to understand such thing.
 

To many of us the observation about the universe expanding may seem a little strange even maybe impossible, but it is true. In 1929, Edwin Hubble announced that his observations of galaxies outside our own Milky Way showed that they were moving away from us with a speed that was proportional to their distance from us. In other words, the more distant the galaxy, the faster it was moving away from us. But does this makes really sense? What about the distance between the Earth and the Sun, is it expanding too? Or what about the distance between the Sun and the center of the Milky Way, is that too expanding? A respond to this is, if there are significant attractive forces between objects, they do not move away from each other as time goes by. Only on the very largest scales, like distances between isolated galaxies or clusters of galaxies, are the attractive forces so weak that the expansion of the universe is able to move objects apart. So the distance between the Sun and the Earth haven’t change over the past years neither the distance between the Sun nor the Milky Way. Something interesting about all this is that the expansion of the universe is accelerating, which is odd because mass creates gravity, gravity creates pull and the pulling must slow the expansion. Therefore scientist had come with a thing that may be the one causing this acceleration and it has been named “dark energy”, something that haven’t get been totally explain.

Another observation is that the universe was hot and now isn’t as hot as before. The theory explain that one second after the Big Bang, the temperature of the universe was 10 billion degrees and was filled with a sea of neutrons, protons, electrons, anti-electrons, photons and neutrinos. As the universe cooled, the neutrons combined with protons to make deuterium, which is an isotope of hydrogen. It also says that during the first three minutes of the universe, most of the deuterium combined to make helium. Trace amounts of lithium were also produced at this time. This makes sense because the universe is mostly hydrogen and helium, with very small amounts of heavier elements. This is in very good agreement with observations and is another major triumph for the Big Bang theory.
 

If the universe is still expanding because of the Big Bang and gas has become cold then the universe should be filled with radiation that is the remnant heat left over from the Big Bang. That makes pretty good sense doesn’t it? This heat is called the “cosmic microwave background radiation”, or CMB.  The way it was discovered, to me is a funny story. It was first observed in 1965 by Arno Penzias and Robert Wilson, but they didn’t know at first that the signals that they were getting were the remnant heat of the Big Bang. They thought that those were cause by pigeons that were in the cone and their pigeon poo. But after removing the pigeons and their leftover’s the microwaves still kept going, they soon realize that those were the leftover radiation of the Big Bang. Today, the CMB radiation is very cold, only 2.725° above absolute zero; which means that million years ago was hotter. If we wanted to hear this radiation all we have to do is get a very old radio and retune it so that you are not on any station and voila, you are hearing the microwaves.
 

In conclusion, for me the Big Bang theory is the best and probably the only way to explain a beginning for our universe. Although it doesn't provide answers to all our questions, it does a better job than any alternative which has yet been proposed. As a theory it has opened my eyes to new things and now when I look at the sky I’m not only going to see stars and a big universe, I’m going to see a big remain of what was the Big Bang.