Have you ever wondered when the material that forms our body start to exist? What are those materials to be precise? Approximately 96% of our body consists of Oxygen, Carbon, Hydrogen, and Nitrogen (sorted from largest mass fraction). Where does that atoms comes from There must be exists some kind of mechanism to "create" those atoms in the first place.
There's no such thing called "time" before the very first moment of the universe. The entire universe emerged from a point that very small even smaller than a single atom, space exploded, universe expanded. Matters and energy were born in this event. This event is called the Big Bang that occurred 13.8 billion years ago.
Few minutes after the Big Bang, few elements were born, Hydrogen, Helium, Lithium, and Beryllium (later two not so abundant compared to first two). The phenomenon itself is called (Big Bang) nucleosynthesis. This phenomenon require very high temperature to make fusion reaction could be happened.
After that, the universe was expanded and causing itself to be cooled.
One of the materials is found, so where's the three?
When the Big Bang happens, the only main product is Helium, because shortly after that the temperature of the universe is below the condition needed by nucelosynthesis to be happened.
The atoms in our body have existed since the first day of the Sun.
You must be kidding. Can you explain me where does that atoms comes from.
In the Sun energy generated by the means of fusion reaction, when it happens the Sun is fusing Hydrogen into heavier atoms. That process is called stellar nucleosynthesis. But our Sun is dominated by one kind of nucleosynthesis, called Proton-Proton Chain Reaction, which is not producing Carbon, Nitrogen, and Oxygen like that happens in CNO Cycle, because the Sun is not yet reaching its Higher Main Sequence. Then Carbon, Nitrogen, and Oxygen is only logical to be created before that.
Emmm. Okay.
By observing the abundance of Hydrogen and Helium then comparing it with the composition of sun we know that the galactic dust (molecular cloud) that formed the Sun is already containing heavier elements than those Hydrogen and Helium.
Long before the Sun was born at roughly 200-300 million years after the Big Bang, the First Stars begin to shine (population III and II stars) which is different from our Sun because these stars are metal free. After that, at roughly 300 million years after the Big Bang these stars doing nucleosynthesis that using Helium as its fuel producing Carbon, Oxygen, and Silicon. Nitrogen is produced before that when the main fuel is still using Hydrogen, nearly at the end phase.
Yep then we know when does Oxygen, Carbon, Hydrogen, and Nitrogen were formed.
But we need to make sure that these elements is same as what formed us today.
By the end of population III and II stars, few of them becoming Supernova and ejecting its materials to the outer space raising more population II stars. Long after that at roughly 8.8 billion years ago earliest population I stars was formed which is metal rich. Long after that long at roughly 4.6-4.57 billion years ago Supernova happened triggering the formation of solar system.
So, here comes the interesting parts, the heavy elements that there were in our solar system is even existed before that Supernova happened. The logical explanation of this was the heavy elements is made by first generation of stars (population II stars) which is approximately created at roughly 300 million years after the big bang or 13.5 billion years ago, long before the first population I stars were formed.
By the time you read this line, we already know origin of the element of life, how can we make sure that those elements is what formed our body? We need to make sure that those elements is same as what formed the Earth.
Thou shalt not create or destroy mass
Matters could escape the atmosphere of Earth if they could move fast enough. The Earth is like a kind of quasi-closed system where there is no mass transfer at its boundary aka atmosphere. Only small amount of Hydrogen and Helium is being escaped as now. The other element is not fast enough to pass the escape velocity of the Earth. Beside that, the magnetic field of the Earth protecting from solar winds which can further increase the escape rate of matters from earth.
The matters on earth only circulates from one form to the another and back, we breathe the same air, life with same elements as our ancestor.
We are born from the stardust (~87%) and the big bang (~9%).
Bad conclusion yep no problem.
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