How old are you? It’s a simple question that we’ve all been asked at some point. But the answer is not that simple; It’s actually surprising when we stop and think about where we come from. The key is to realize that the elements that make up our bodies are older than we think, even older than our planet.
This is the explanation: it is often said that we are stardust; very nice, I’ve heard it before, but it’s not so true. If we ask ourselves how old our bodies are, we must analyze what the human body actually is. Our bodies are mostly made up of water (around 60% by weight). That’s H2O, two hydrogen atoms for every oxygen, meaning that most of the roughly 7,000 quadrillion atoms that make us up are hydrogen, about 62% of the number. And how old are those hydrogen atoms? Again, the answer is not simple. Hydrogen atoms consist of one proton and one electron. According to our latest calculations, protons appeared in the universe a little less than 13,813 million years ago, with an error of 38 million years up or down.
Specifically, the protons of virtually all hydrogen atoms that exist today appeared from the first second after the Big Bang and in the first 3 minutes counted from that moment 13,813 million years ago. From the first second of our universe, the quarks that previously dominated the entire universe disappeared to form protons and neutrons. Also, at that distant time (but it happened next to here, in the same place from where you read this article – and anywhere else -), electrons were already quite oldwhich formed between one millionth and one billionth of a second after the big bang.
But the electrons and protons did not combine to form hydrogen until about 380,000 years after the big bang. So 62% of the atoms in my body and yours (which make up 8% of its mass) are a whopping more than three times the age of our planet, which is when the sphere where we live was formed. And this leads us to say that we are not so much stardust as is often said; Rather, our atoms were conceived for the most part shortly after the big bang.
Going back to our composition in terms of molecules and their atoms, we left the oxygen hanging. In addition, this element is very important, because although hydrogen is the most abundant atom in our body, if we look at the mass, it is dominated by oxygen, which is about 16 times heavier than the proton and electron that we talked about. 65% of our matter is made up of oxygen.
And how old is the oxygen that dominates what we see on the scale? There are astrophysicists who have been thinking about this for decades, looking for oxygen, which is true, it is easy to find in space, in increasingly distant galaxies. Oxygen was seen when the universe was less than 3% of its current age. Observing distant galaxies means looking back in time because they are so far away that light takes almost forever to reach us. And that delay allows us travel in space-time. Our studies tell us that three-quarters of the oxygen existing in the universe today was formed in the first half of the universe’s history, and the other quarter later. Further out in space and earlier in time, 50% of the oxygen we have here today was formed in the first quarter of the universe’s history, in the first 3.5 billion years after the big bang, when it was still about 5 billion years old. years to go before the Sun and Earth appear, which in turn are 4.5 billion years old. We do not present more data on the formation of oxygen, although some exist, and conclude that on average our oxygen may be about 10.5 billion years old. We are the same age.
We are oxygen, carbon and hydrogen
If we keep asking ourselves how old we are when we calculate when the elements that make us up, we have to move to the next type of atom in the mass contribution to our scale. That element is carbon, which makes up almost 20% of our mass. Carbon, more oxygen, more hydrogen already make up 93% of our body mass. Carbon is somewhat more difficult to observe, but with a radio telescope we can go almost as far and as early in the history of the universe as oxygen.
Up until now, we have more or less been able to calculate the actual age of our bodies. We will leave the creation of the other elements (nitrogen, calcium and phosphorus are others of fundamental interest) as a small correction that we do not want to get into. We don’t even stop at the fact that any atom actually comes from the primordial hydrogen that appeared in the first second of our universe, mixed in lunch boxes stellar, with the help of other very old particles like photons (which weren’t always there).
We could do a similar account for a planet, taking into account its atoms and where they came from and when they appeared. How does our age compare to our planet in terms of how old our atoms are? A third of Earth’s mass is iron, slightly less oxygen, and another third is dominated by silicon and magnesium, each nearly 15% by mass, leaving only room (or rather mass) for some sulfur, nickel, cadmium. , etc.
When did the iron or silicon that we have on our planet originate? Well, it’s much more difficult to answer than in the case of oxygen. Iron can be detected in very distant objects, although it is extremely difficult. We discovered iron and silicon near supermassive black holes that existed when the universe was 5% of its current age, but these elements certainly appeared much more slowly than oxygen: we need to continue investigating to confirm this.
We leave here this journey through the history of our bodies. We are not getting to where matter that has been dancing through the universe for ages has coalesced like this and acquired something that philosophy and religion have been trying to explain for several millennia. Pieces of our bodies have long ago filled a portion of the cosmic void and will return to it, albeit filling it a little less each time.
The cosmic void It is a section in which our knowledge about the universe is qualitatively and quantitatively presented. It aims to explain the importance of understanding the cosmos not only from a scientific point of view, but also from a philosophical, social and economic point of view. The name “space vacuum” refers to the fact that the universe is and is largely empty, with less than one atom per cubic meter, even though there are paradoxically quintillion atoms per meter in our environment. cubic, which invites us to reflect on our existence and the presence of life in the universe. The section is assembled Pablo G. Perez Gonzálezresearcher at the Astrobiological Center, a Eva VillaverováDirector of the Space and Society Office of the Spanish Space Agency and Research Professor at the Institute of Astrophysics of the Canary Islands.
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