Did you ever wonder that where you came from? That is the stuff which inside your body like your organs, muscles, bones…etc. All these things are made of various atom & molecules. But from where did these little ingredients come? & how were they made? The answer to all these questions will take us back to a time long ago when the universe was much different than it is now. However, the physics was the same.
The early universe expanded after the big bang for only three seconds before it cooled to a state where subatomic particles assembled into atoms. Hydrogen atoms formed 1st since they are the simplest type of atom. Hydrogen atoms contain only 1 proton in its nucleus which makes it number 1 on the periodic table of all elements. After the universe aged a little (roughly 300 million years), the hydrogen atoms started to clump together under the gravity force. The pressure at the center grew larger, as these clumps grew in size. When the temperature reached to 15 million degrees F, the pressure caused the hydrogen to fuse their nuclei together. This process is known as the nuclear fusion. The positively charged nuclei naturally repel each other. However, under the high temperatures & pressure, the nuclei are moving fast enough to smash together & fuse. When the two proton nuclei of the hydrogen atoms fuse, they form the nucleus consisting of 2 protons. Some electrons also combine with the protons to form neutrons & neutrinos. Under the nuclear forces, these neutrons also bind to the nucleus helping it to remain more stable. An atom with 2 protons in its nucleus is Helium. That’s why helium is number 2 on the periodic table of elements. The fusion process also releases the much more of energy in which some of the hydrogen mass converts into light energy. This conversion of mass into energy uses Einstein’s famous equation: E=mc2.
Our universe has a bunch of large clumps of hydrogen fusing together to create helium while releasing large amounts of light at this point. This is what we commonly call a star! In fact, our sun is doing this right now as we read (or speak). As a star age, it then fuses the helium with hydrogen to form lithium which has three protons in its nucleus. At the periodic table take a look to see which number it is. This fusion process continues to create larger & larger nuclei. The fourth, the fifth & all the way up to 26.
This is a general idea but it’s not exactly this easy. We have to remember that this is, in fact, nuclear physics that we are dealing with here. It looks like full of beauty & simple picture as we just described but up close it is actually an intricate jigsaw puzzle.
Through the periodic table, the fusion process doesn’t actually create the elements in order. In fact, the process jumps around & some fused nuclei decay down to lower elements that were skipped over. Fusion also creates the neutrons which combine with atoms to create the isotopes which act like atomic cousins. Overall, we can say that a star produces all elements up to the iron in periodic table through the fusion process. The details of this process are fascinating, yet they deter us from the answering of question at hand.
The element with 26 (twenty-six) protons in its nucleus is iron. It turns out that this is the last element which is created. To create the higher elements, fusion requires more energy than it produces. We mentioned earlier that a star glows because the fusing atoms release the energy (E=mc2). However, the amount of energy released becomes smaller & smaller as the atoms grow larger. Eventually there is no energy released at iron & for elements beyond the iron more energy is need for fusion than gravitational pressure can provide.
After a star has created enough iron, fusion ceases & the hot burning core begins to cool. Up until this point the hot core of the star erupting outwards & preventing gravity from collapsing the star. Now that the star has cooled, the core no longer expands & gravity quickly collapses the star. The star implodes with enough energy to immediately fuse some of atoms into the higher elements like Nickel, Gold, Uranium, Krypton, etc. This quick & violent implosion releases an enormous amount of energy that explodes the star. This is what we call a supernova! Astrophysicists are still not exactly certain about the details of how the supernova explodes. Hopefully you can figure it out someday!
The exploded remains from a supernova travel through-out the universe only to someday clump together with other stardust & give birth to a new star. This is the life of our universe.
Now that we have established that every element in the periodic table aside from the hydrogen is essentially stardust, we have to determine how much of our body is made up of Stardust. If we know how many of the hydrogen atoms are in our body, then we can say that the rest is stardust. Our body is composed of roughly 7×1027 atoms. That is a lot of atoms! Try writing that number out on the piece of paper: 7 with 27 zeros behind it. We roughly say because if you pluck a hair or pick your nose there might be slightly less. Now it turns out that of those billions of billion atoms, 4.2×1027 of them are hydrogen. Remember that hydrogen is big bang dust & not stardust. This leaves 2.8×1027 atoms of stardust. Thus, in our body, the amount of stardust atoms is 40%.
Since stardust atoms are the heavier elements, the percentage of the star mass in our body is much more impressive. In our body, most of the hydrogen floats around in the form of water. The human body is about 60% water & hydrogen only accounts for 11% of that water mass. Even though water consists of 2 hydrogen atoms for every oxygen, hydrogen has much less mass. 93% of the mass, which we can conclude that in our body is stardust. Just think, long ago someone may have wished upon a star which you are made of.