What has this to do with physics? Well, the question today is were did the carbon come from and how did physics enable this discovery to take place?
Current thinking says the following...
Carbon is probably created by the triple alpha process. I say probably, because like many things in physics we have no real way to test it, but it makes sense in a way and it is the best theory we have.
It was discovered by Astrophysicist Fred Hoyle a bloke from Yorkshire, England. His thinking went something like this.
we are here, and we are made of carbon, so carbon must have originated somehow. The only physically conceivable way is through the triple alpha processes.
He then went on to make predictions about the nature of Carbon should this process be true and lo and behold he turned out to be correct.
Now here is an interesting thing, up until this discovery Fred had been an atheist, but this process seemed so unlikely to him that he could not shake the belief that there must have been some guiding hand at work. Physics turned an atheist into a believer!
So the triple alpha process, what is it?
Helium is the second element in the periodic table and a gas. Its center is made up of 2 protons and 2 neutrons. The center of a helium atom is called an alpha particle. The reason it is called an alpha particle dates back to the early work on radioactivity.
Around 1900 a Physicist called Rutherford had managed to separated radiation into three types: alpha, beta, and gamma rays based on how these mysterious rays penetrated objects and caused ionization. It was later realised that the alpha particle was actually a Helium nucleus. Since that time, the Helium nucleus has been known as an alpha particle.
The triple alpha process is where 3 helium centers join together to create a single nucleus consisting of 6 protons and 6 neutrons, which is Carbon!
Ok, big deal! Well it is because without it we would not be here. The triple alpha process is actually a 2 stage process. Two alpha particles join together to create a Beryllium nucleus, then a third alpha particle bashes into the Beryllium particle to create Carbon. The problem here though is that the Beryllium particle formed from the two alpha particle bashing into each other is very unstable and disintegrates back into two alpha particles almost immediately. So this means that the conditions for creating Carbon must be fairly specific and it turns out they are.
This tells us something about the way carbon based life must have evolved. The triple alpha process requires high temperatures and pressures if it is correct. This means that carbon could not have existed shortly after the big bang (more on the big bang elsewhere). While the temperatures required to create Carbon existed for a very short time after the Big Bang, the alpha particles and the pressure required did not. So there could be no Carbon produced.
If the big bang model is true then the universe was completely devoid of carbon based life for literally billions of years after its creation We had to wait for stars to go through the process of creating helium and literally grow old and dying.
Young stars are made of hydrogen, it is the fuel of the star. As it “burns” (it does not literally burn) the hydrogen centers join together to form helium giving out energy in the process. Eventually after millions or billions of years the star begins to run short of hydrogen. When the star runs short of hydrogen it starts to collapse and the pressure and temperature inside the star increases.
When the temperature and pressure increase within the star the helium centers begin to react with one another creating Beryllium. While this form of Beryllium is massively unstable it sometimes survives long enough to react with a third alpha particle to create Carbon.
Carbon, once it is made, is really stable, even when it is inside a star.
When the star eventually dies it can do one of several things. If it goes supernova (explodes) the Carbon along with other elements created in the star are blasted out into space as dust.
One amazing thing about a supernova is the time scales involved. A star can last for billions of years. Our own star is expected to live about 10 billion years. When it goes through its final stage everything happens not in years or even hours. The final stage of a stars life happens in seconds. When the star finally reaches a point where it does not have the fuel left to stop itself collapsing it does so in spectacular fashion.
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| Supernova, bottom left, brighter than the galaxy center |
There is some evidence to show that during this short interval a supernova can radiate as much energy as the sun is expected to emit over its entire life span of 10 billion years. This is one of those statements that does not mean a great deal, for starters, how can anyone actually even imagine how much energy the sun produces in a single second, never mind 10 billion years, it's just not possible.
What is easier to comprehend is the realisation that it can glow so brightly that it can be brighter than an entire galaxy. This can last for weeks or even months.
It is currently believed that this stellar dust starts to stick together forming larger particles that become small rocks. The rocks join other rocks to become asteroids. The asteroids hit other steroids and become bigger and bigger, eventually, in some cases, forming solid planets.
In the case of our planet the Carbon created in stars enabled the creation of life and this for me is the greatest thing about life and Carbon.
Life on earth is based on Carbon. Carbon comes from stars. Each and every human being is made from carbon made in stars.
WE ARE LITERALLY MADE FROM STARS!
How cool is that.
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