by Mel cross posted from her blog When Cows and Kids Collide
(all images in this posting belong to When Cows and Kids Collide)
Welcome back to the crazy world of young-Earth creationism.
Today, we cover chapter 7 of The New Answers Book One by Ken Ham. This chapter tries to disprove carbon-14 dating in specific and radioactive dating in general. The author of this chapter – Mike Riddle – and I agree on one thing: a basic overview or review of atomic structure is needed.
Let’s start at the outside of a carbon atom. As we approach the atom, will first enter the outer shell of electrons. In carbon, the outer shell has four electrons. In the most recent understanding of atomic structure, scientists know that electrons are found within a certain three-dimensional area but are not stuck in tracks as the more traditional Bohr model.
As we move in past the outer electrons, we move into the inner electron shell that has two electrons in it.
In the majority of chemistry, we’d spend more time talking about the electrons because they are the basis of most chemistry. Since YEC has decided to take on nuclear chemistry, all we need to remember is that electrons are very small compared to protons and neutrons and electrons are negatively charged.
Moving into the nucleus, we see two different particles in the nucleus. Protons are positively charged. Neutrons have a neutral charge. In terms of mass, one proton or one neutron has the same mass as over 2,000 electrons. Each element is determined by the number of protons. All carbon atoms have six protons. Each (with a few exceptions) element can have differing number of neutrons. Carbon can have six neutrons, seven neutrons or eight neutrons.
We determine the mass of each atom by adding up the total number of protons and neutrons. We use the term “isotope” to describe atoms of the same element that have different number of neutrons.
The diagram above is of carbon-12. You can tell it’s carbon because there are six protons. The “12” means there are a total of twelve protons and neutrons. Carbon-12 is the most common type of carbon atom; 99% of carbon atoms are carbon-12.
See if you can figure out the mass of the next diagram:
It’s carbon-14. Carbon-14 is very rare and makes up a tiny percentage of total carbon atoms.
What about this diagram?
Yup, this is carbon-13. Carbon-13 makes up a little under 1% of the the total carbon engines.
Why is carbon-14 so rare? Carbon-14 is very unstable. Carbon-14 will undergo radioactive decay and change into nitrogen-14. Here’s how it works: Let’s zoom in close to a neutron.
Much to my surprise when I learned this, a neutron is actually a proton with a single electron tightly bound to it. The electron is so tiny that it doesn’t affect the mass of the neutron. In radioactive decay, the bond between the electron and proton that makes up a neutron breaks. The electron is thrown free of the atom and the proton stays.
Long story short: Carbon-14 has a neutron split into a proton and an electron. The electron is lost, a massive amount of energy is released, and the atom becomes nitrogen-14 because it now has 7 protons and 7 neutrons.
How do scientists use carbon-14 to date objects?
Carbon-14 dating is only used on formerly living items like wood or a fossil. (This is an important point that Riddle mentions in passing, then violates over and over again.) When an organism is alive, carbon is being added to the organism through photosynthesis or through eating food. The ratio of carbon-14 to carbon-12 in the body is equal to the ratio of the two isotopes of carbon in the atmosphere. For simpicity’s sake, I’m going to follow Riddle’s lead and say that the ratio is one carbon-14 atom for every 1,000,000,000 (trillion) carbon-12 atoms. Once the organism dies, the carbon-14 decays while the carbon-12 is unchanged.
We know the rate at which carbon-14 decays into nitrogen-14. In any sample of carbon-14, approximately half of the carbon-14 atoms will decay into nitrogen-14 in 5715 years. This means that the half-life of carbon-14 is 5715 years.
Since there isn’t any way of knowing exactly how many carbon-14 atoms started in the sample that is being dated, scientist make a ratio of the amount of carbon-14 to the amount of carbon-12. By comparing the ratio of carbon-14 to carbon-12 in the fossil to the ratio in the atmosphere, you can get an accurate date since the death of the organism.
Let’s run through a scenario. An oak tree is blown down in a storm. What would we expect to see (theoretically) if we could count the C-14 and C-12 atoms at 0 half-lives? We would see that none of the C-14 has had time to decay, so we could count all of the C-14 atoms. The C-12 atoms are all intact, so we could count all of those and we would find that the ratio of C-14 to C-12 is about 1 to 1 trillion.
I’m going to start a table – very similar to one in The New Answers – so we can keep track of the changes over time.
We return 5715 years later and take another sample from the oak tree at one half-life. Half of the C-14 atoms have decayed into N-14 and don’t show up in our count. All of the C-12 atoms are still present. The ratio of C-14 to C-12 atoms is now 1 for every 2 trillion atoms which is half as small as the original. Let me jot that down.
We come back in another 5715 years and repeat. Another 50% of the C-14 atoms have decayed so only 25% of the original C-14 is left. Since the C-12 is still unchanged, the ratio of C-14 to C-12 is now 1 C-14 atom for every 4 trillion C-12 atoms.
We come back every 5715 years. The amount of C-14 drops by half each time. The amount of C-12 is constant (unchanging), so the ratio of C-14 to C-12 drops by half each time.
If you are more of a visual person, here’s a graph of the percentage remaining C-14 per half-life. (Mathy nerd side note: The “Percentage C-14 remaining” axis should actually be asymptotic which means it should approach 100% but never touch it. This is because C-14 atoms always have a small probablility of decaying into N-14 at any moment in time. Because of that, you can’t get a pure 100% sample of C-14. I feel better.)
This is where Riddle stops giving explanations and starts shooting holes in C-14 dating. I’ll debunk his mistruths in the next post, but I want to show you why he stops at 5 half-lives instead of 10 or 15 or 20.
Here’s the table expanded out to 15 half-lives.
Notice that there is a natural stopping point at 14-15 half-lives: The ratio of C-14 to C-12 at 15 half lives is 1 atom of C-14 for every 32,768,000,000,000 atoms of C-12. The atoms of C-14 aren’t completely gone; in fact, statistically there will always be a few C-14 atoms floating around. The problem is that trying to get a good signal on the C-14 atoms is impossible.
For the visual folks:
(Mathy nerd bit 2: The “Number of Half-Lives” axis is also asymptoic. It will never hit zero because cosmic rays and radiation from nearby atoms can cause a small number of N-14 atoms to change into C-14.)
The fast way to prove Riddle wrong: If YEC is true, C-14 dating shouldn’t work at all.
1) If YEC is true, carbon-14 dating of any organic fossil should give us a half-life of 1.2 or less.
A picture helps:
The red line is slightly over 7,000 years. If YEC is true, nothing can give us a date of over 7,000 years or 1.2 C-14 half-lives. Oddly enough, Riddle NEVER brings this point up. Ever.
2) For YEC to be true, the C-14 dates must be off by a magnitude of 16,384 times.
In other words, when Riddle starts poking holes, the answer must be able to cause the YEC ratio of 1 atom of C-14 to 2 trillion atoms of C-12 to somehow appear as 1 atom of C-14 to 32,768 trillion atoms. A different way of saying it: YEC is arguing that every atom of C-14 we see in a 85,000 year old fossil is off by 16,383 atoms of C-14.
Good luck with that.