BUILDING THE UNIVERSE

 Gravity: The most popular of the four fundamental forces and also the least understood by physicists out of the four.  It is the weakest force out of the four but what makes it dominate the universe is its range. A gravitational field is thought to extend infinitely meaning that gravity can come into play even at large distances, unlike the strong and weak nuclear forces with the size of their ranges being of nuclear lengths (around 10-15m). What about the electromagnetic force (the force that is associated with magnets and electricity- yes, they are both interrelated)? The electromagnetic force has the same range as that of Gravitation, but, unlike Gravitation-which requires only mass,the electromagnetic force requires charges and because very few charges are separated(almost all charges clump together-positively charged proton and  negatively charged electrons to form atoms), and they become neutral, meaning their effects would only be felt at extremely tiny distances. This leaves the gravitational force as the only candidate for building the large-scale structures in our cosmos, though at smaller scales, electromagnetic forces reign. Electromagnetic forces keep everything from your phone to your favourite pizza and yes, your body too from falling apart. The electromagnetic bind matter together which cannot be bind together by gravity and can also cause repulsions in bodies with the same charge(both positive or both negative) to repel, thereby undoing the effects of gravity. A common example of this repulsion is the explanation of why you and all the other things around you are still at the surface of the earth (considering you are not in a plane or flying right now) and not at the centre of the earth, which should be the case because the earth and you are attracting each other towards each other’s centre of mass1. The reason for this is that the protons in the molecules of your body (or your footwear) are repelled by the protons in the molecules of the surface beneath you. This causes you to stay where you are and levitate at a height of about 10-10m in the air from the ground. Even while you are sitting, your molecules aren’t touching the molecules of the chair but are floating at a similar height. 

Let’s go back to our initial discussion about gravity. The early universe was filled with high energy particles moving around, bumping into each other, losing energy as electromagnetic radiation (or light) and separating again, as these particles had a lot of energy. After the particles lost a significant amount of energy, they started combining together. Quarks formed protons and neutrons and these, in turn, formed nuclei of atoms. These formed due to the strong binding force of strong force. Then as electrons started losing their energy too, electromagnetic forces were finally significant enough to bind electrons around a nucleus and form an atom. After atoms were formed, gravity took it from there and built this universe. An atom is neutral (no positive or negative charge) which means electromagnetic forces did not play a significant role later on, though initially, the weak electromagnetic forces between atoms made them cluster together. These clusters, as they became more and more massive, attracted even more matter due to their gravitational attraction. Eventually, these became massive enough to become stars.

Stars made star clusters and star clusters formed Galaxies. The first galaxies took shape as little as one billion years after the Big Bang, which probably took place about 13 billion to 14 billion years ago. At the centre of most galaxies lies a supermassive black hole. Astrophysicists are still puzzled by how they were formed but we do know that they played an important role in forming our galaxies. Although galaxies come in different shapes and sizes, it is believed that most galaxies were formed as spiral galaxies but over time evolved into other shapes we see. Our galaxy, the Milky Way is still a spiral though like the one below.

AI Generated using Gemini :)