Are We Really Made of Star Stuff?
Although we don’t know if there was a Big Bang or Big Bounce for sure, we know “all matter and its interactions are explained by the standard model of particle physics, and those standard model particles make up the elements. We know that, as far as we can tell, all those particles originated at the center of the bang or bounce and consequently transformed via nucleosynthesis (nuclear fusion and fission in stars). We know this is how all the elements are made (from hydrogen and helium, to more complex elements fused in later stellar explosions).
While this isn’t a theory of everything, as not even the standard model currently explains some odd balls like dark matter for instance, we can say our bodies and everything else around us “is made of star stuff” and lots of “empty space” following the rules of Pauli exclusion (i.e. nothing with mass can directly touch another thing with mass).
On this page, we look the Big Bang theory, the Big Bounce theory, and generally at stellar nucleosynthesis and compare it to elemental makeup of the human body to show that Carl Sagan’s claim that “we are star stuff” is true.
How Much of Me Is “Star Stuff?”. The answer is all of it… this video explains. Make sure to watch the more heady PBS videos below too.
FACT: The human body is created from elements, which are created from quantum particles, which are fused into elements in stars. This is true without exception. All proteins, cells, etc are composed of elements. Elements are made in stars. We are star stuff. See the composition of the human body.
Carl Sagan’s quote at 2:20 “the cosmos is also within us, we’re made of star stuff”. One could say “we are the universe’s way of experiencing itself”, but one would be dipping their toes in metaphysics at that point (feel free, the water is warm). The fact that we are made of star stuff is actual science. The elements in our body were formed in stars.
What is the Big Bang Theory?
The Big Bang theory says that all the energy in the universe today (all non-empty space) began as a single central point of condensed energy at the start of our universe (Big Bang Nucleosynthesis). That point expanded and formed the elementary particles and the four fundamental forces (mass-energy). Those particles and forces came together to form composite particles, which, in turn, created atoms. Atoms are the elements that use chemical bonds to form molecules. Molecules combine, in turn, to make cells and bacteria, which formed us (and everything else).
Well, almost, actually that Big Bang nucleosynthesis process only formed basic elements like Hydrogen, to get something with a higher proton number (each element has a higher proton number) we need another really big bang. Luckily, that is just what happens when the right type of stars explode causing Stellar Nucleosynthesis.
What is Big Bounce Theory?
Big Bounce is like the big bang but it describes in oscillation where instead of everything banging out and expanding into nothing, everything expands and contracts and expands again. Whether it was a bang or a bounce, we can confirm that the basis of all matter from the elements, to the four interactions, to the standard model particles is “star stuff”.
Below we will assume the Big Bang is true (as its a longer running theory) regardless, the rest holds up under either theory.
The Big Bang might have been just a Big Bounce.
The nuclear reactions that happen in stars form elements; these elements are then released when stars die and explode.
These smaller bangs (fusion and fission from dying stars) produce all the elements not created in the big bang. The mechanics aren’t difficult. The more complex elements with higher proton numbers are harder to form and more likely to decay. All lighter elements collapse into iron, and heavy iron likes to explode causing stellar nucleosynthesis, which forms the other more massive elements. This overview is simplified; the process warrants a broader explanation in a video.
Nucleosynthesis | Space Time | PBS Digital Studios.
Big Bang Theory and the First Law of Thermodynamics
We can be sure that new energy wasn’t created after the big bang due to the first law of thermodynamics which states all energy in a closed system can’t be created or destroyed (meaning all mass-energy for our purposes).
Although we don’t know how the energy got there in the first place, assuming our universe is a closed system, we can conclude that particles in your body are the same particles from the big bang (although some are transformed from nucleosynthesis, no new mass-energy was ever created).
Why the Big Bang Definitely Happened | Space Time | PBS Digital Studios. I can’t pick a favorite band, but I can pick a favorite space show on YouTube. This would be it. Please watch the PBS Big Bang explainer videos on this page.
Composition of the Human Body
So we know the basics of the nucleosynthesis now, but we haven’t covered what is in our body. This chart below shows the composition of the human body (source), and the chart below shows the periodic table of elements arranged by atomic mass (proton number).
Remember most of the massive elements are formed in stars. while Hydrogen and other basic elements may have formed in the Big Bang. Generally, things have transformed, but the core quantum material is the same star stuff.
Chemistry, biology, and physics confirm we are made of star stuff, but that doesn’t mean our theories of the big bang and evolution are perfect. Science is all about proving ourselves wrong, and putting theories to the test ensuring they working over and over again.
See the video below for a look at “what is wrong with the big bang, as it stands in 2016.”
What’s Wrong With the Big Bang Theory? | Space Time | PBS Digital Studios.
FACT: Evolution and the big bang are scientific theories. Learn more about what that means here.
From the Big Bang to You. A Super Simple Big Bang Explainer
The big bang describes the rapid expansion from one singularity to what we know today. It also proves (assuming the big bang theory, and what we know about chemistry and biology, is right) that we are all made of star stuff.
Assuming the big bang theory is correct, the big bang as we know it goes like this:
- At the start of the big bang all energy is condensed into one point.
- New energy can’t be created or destroyed, so all the energy that will become the universe is at that point (unless that point was able to break the first law of thermodynamics, then at least shortly after that point, all energy that will exist).
- The singular point starts to expand releasing superheated matter. In fractions of a second, the universe expanded creating the four fundamental forces and their carrier quantum particles that we know today.
- After some expansion, but still in that same second the universe began, the “star stuff” started to cool and stop some quark creation.
- Minutes later quantum particles formed atoms, which went on to form the element hydrogen (the simplest element).
- Hydrogen “gas” was brought together by gravity since mass creates gravity (curves spacetime around matter) and forms stars.
- Stars act as incubators, creating new elements and releasing them when they die in just the right way (stellar nucleosynthesis). The gravity and heat of stars fuse elements in nuclear reactions. Some superheated stars created heavier elements. The process repeated to create the elements of the universe. Some elements decay in less massive ones after fusion.
- Over time, the gas and stars came together to form galaxies, solar systems, and planets. Old stars died and gave birth to new stars and planets, and the process repeats as the universe continues to expand.
- About 13.8 billion years ago, potentially as shortly as 1/2 million years after the big bang, the “chemistry of life” is thought to have begun.
For over the past 13.8 billion years life has grown across the universe in whatever places it can. The elementary particles form composite particles, those particles form atoms, then atoms form elements, elements form living and non-living matter including single-celled organisms and bacteria, single-celled organisms form multi-celled organisms, multi-celled organism forms plants and animals, humans are animals. We are made of “star stuff” just like everything else in the universe.
TIP: To explore further, and shed light on why the above is true, take a look at mass-energy equivalence.
How special relativity and Hubble’s telescope opened the doors of our understanding.