The Universe - Fusion Makes Elements Form

You know that everything in the universe is made up of atoms and that those atoms are all made up of smaller particles. In order to form different elements, we have to push those particles together in a process called fusion (something that requires extremely high temperatures and pressures) or break atoms apart in a process called fission. Look at the timeline below and notice the elements were formed from the Big Bang.

Notice that it took 300,000 years to finally form the first atoms. Up until that point, subatomic particles such as protons, electrons, and neutrons were the only matter flying around. When all those particles became fused, they formed the elements shown in the illustration. Looking at the periodic table of elements, what do you notice about the three elements formed by the Big Bang? As time went on the universe cooled (thus the change in color from red to blue) and there wasn't enough pressure to fuse atoms anymore, so hydrogen and helium began to collect together in galaxies.

As galaxies formed, there began to be very massive groups of hydrogen and helium atoms. As the pressure grew, eventually there was enough pressure to fuse the hydrogen into helium and our first stars formed. Stars "burn" because they release large amounts of energy when hydrogen fuses to form helium and heavier elements such as carbon. The process of nuclear fusion starts when two hydrogen atoms collide and produces energy, two subatomic particles called neutrinos and positrons, and an atom of helium. In a normal star, there is enough pressure to fuse larger atoms and form elements as heavy as iron. If the star is extremely massive, it will die in a violent explosion called a supernova. During a supernova, there is so much energy released, that even heavier elements than iron are able to form by fusion. The elements formed on the inside of a star are what make up our planet, including all life on it (that means you).

So, what did you notice about the elements formed in the Big Bang? How do they differ from those that formed inside stars? How do we know all this? Explore how scientists have learned this.