Introduction
Welcome back to yet another article! This is the 5th article in a series of articles meant to introduce concepts in astronomy to you all! In this article, we’ll be talking about cosmology and the universe as a whole. We’ll be looking at such large scales that our minds will certainly be blown away by the end of this article. Cosmology deals with the nature of the universe and we’ll be talking about the origin and future of the universe, the scale of the universe, dark energy, redshift, and black holes.
The Big Bang
First, we’ll talk about the Big Bang. The Big Bang is what scientists believed occurred at the very beginning of time. The universe started off as a singularity or a single point of infinite density and mass. You could think of a singularity as everything and everyone compressed into a tiny point in space. Yeah, mind blowing I know. During the first moments of the universe’s life, there was only a single fundamental force and it was so hot that particles still could not form. Later, the four fundamental forces would be separated into what we now know as gravity, electromagnetism, the strong nuclear force, and the weak nuclear force. Then after all that, the first matter forms but only individual particles like protons and neutrons would form, also known as the building blocks of atoms. This occurred all during the first second of our universe’s life.
From the first second to the first 20 minutes, electrons would form, another fundamental building block of atoms. Also, photons would also form, bringing light. Only 380,000 years later, the first atoms would form when the universe cooled down enough to allow electrons and nuclei to combine together. 400 million to 1 billion years later, the first stars and galaxies would form. Our Solar System only formed 9 billion years later after the Big Bang.
Expansion of the Universe
If I asked you whether the universe was expanding, contracting, or staying constant, what would you say? If you picked expanding or contracting, what can you say about the rate of expansion or contraction? Is it increasing or decreasing? These are all quite tricky questions, but take a moment to think about it before reading ahead. Well, it turns out that the universe is expanding at an accelerating rate due to dark energy. The reason is because dark energy counters gravity, so while gravity causes contraction, dark energy causes expansion. In addition, a fun fact is that dark energy is invisible but present everywhere; in fact, it makes up 68% of the universe’s mass-energy content.
Redshift
Have you ever wondered why distant stars always appear to be red? Well, one possible reason is due to the redshift of the stars and galaxies. Redshift occurs when stars are rapidly moving away from us and in turn, the light emitted by the stars get lengthened so that the wavelength becomes longer and appears to be red. Note that out of all the visible light colors, red light has the longest wavelength. The concept that stars are literally flying away from us is actually a misconception. The expansion of the universe is less like a literal expansion and more like points on the surface of a balloon becoming further and further apart as the balloon gets blown up. That’s a really nice analogy to think about the expansion of the universe.
Black Holes
A black hole forms after a supermassive star dies and goes through a supernova or the explosion of the star. After the star rapidly expands, it then eventually collapses on itself and becomes a black hole. A black hole is also the concept of the singularity we mentioned earlier, as it is a theoretical point of infinite density. Black holes also have an event horizon where not even light can escape past them. It is thought that a person could theoretically see the back of their head when they are at the event horizon because light travels in a circle, so light from the back of the head comes to the eyes!!
Future of the Universe
Let’s briefly touch on some theories regarding the future of our universe. There are three main theories: the Big Rip, the Big Crunch, and the Big Freeze. The Big Rip hypothesizes that as the universe expands, everything will be torn apart. This is thought to be caused by the expansion of dark energy being faster than the expansion of the universe, and it can be thought of as a water balloon being ripped apart because there was too much water. The Big Freeze hypothesizes that as the universe expands, eventually heat will be so spread out that the universe will sort of shut down and nothing can really take place anymore. It’s kind of like soup getting very cold after a long time. The Big Crunch hypothesizes that the universe will not expand forever but will eventually collapse on itself and become another singularity again. This singularity could then start to expand and start another universe. This is a really cool idea because who knows, we might just be one universe of many universes formed from many many big bangs.
Scale of the Universe
Lastly, let's end on a fun note about the scale of the universe. Check out this video to experience how massive the universe truly is. Here are some cool facts regarding the scale of our universe!
There are around 100 billion to 400 billion stars in the Milky Way Galaxy and around 100 billion to 2 trillion galaxies in the Observable Universe!
Theoretically, there could be tons and tons of universes or even infinite parallel universes!
If the age of the universe was 1 year, then Columbus would “discover” America within the last second of the year!
That's it for this article. See you all next time!
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