Superhero Puzzle #905 — “Carbon dating shows … “

From Agents of S.H.I.E.L.D. season 4 episode 3: what’s wrong with this dialogue?

The scene: the agents are in the lab and Fitz as just discovered sand particles from an ancient scroll he supposed would be a clue to unlocking his love, Jemma Simmons, from the dark matter obelisk, are not what they appear to be …

  • Fitz: OK, the sand itself … not unusual. Mostly silicon dioxide particles just like on Earth.
  • Coulson: But you’re saying this sand is not from Earth?
  • Bobbi: Sir, carbon dating shows that …
  • Fitz: [interrupting] It pre-dates the Earth by a billion years.

Could it be that sand is not made from silicon dioxide particles?

Nope. Sand is quartz, mostly, and that is SiO2 (silicon dioxide) mostly.

Could it be that there is no carbon in sand?

Maybe, but that is not bad science. Silicon dioxide has no carbon atoms in it of course. But any quantity of naturally occurring sand is full of impurities, some organic some inorganic, either of which type could contain carbon.

Might it be that sand is only found on Earth? (If you thought this was the bad science you had to be kidding!)

Could it be the title of this blog post gives it way? Is “carbon dating” phony science?

Certainly not! If you attended the bare minimum of science classes at school then you should know carbon dating examines the ratio of radioactive carbon-14 to carbon-12 atoms in fossils and other artifacts.

The answer is the split dialogue, “carbon dating shows that it pre-dates the Earth by a billion years.”

Why? Carbon dating relies upon two critical things:

    1. Radioactive Carbon-14 is created by cosmic ray bombardment of naturally occurring Nitrogen-14 in the earth’s atmosphere. Nitrogen-14 is highly unstable and decays almost immediately liberating a proton and forming radioactive carbon-14.

So far OK. Plenty of other planets would also have nitrogen atmospheres.

    1. The atmospheric Carbon-14 will combine with oxygen readily to form carbon dioxide.
    2. Living organisms breath in CO2. A certain ratio of which will be radioactive CO2 due to the carbon-14. Organisms also breath in normal non-radioactive CO2 containing stable carbon-12.

Still OK. It would be entirely plausible that life on other planets also uses oxygen and carbon dioxide for respiration.

    1. When an organism dies it no longer takes in the radioactive CO2. So the naturally occurring ratio of carbon-14 to carbon-12 in dead matter slowly decays over time at a predictable rate according to the decay rate of unstable carbon-14. This mechanism creates a natural fossil clock.

Still uncontroversial. The same natural fossil dating clock mechanism would occur on other planets.

So where is the telly bad scifi?

  • Question: How long does the carbon-14 clock work? Answer: only roughly ten to 20 times as long as the radioactive half life of carbon-14 (the time it takes half of a sample of carbon-14 to decay).
  • The half-life of carbon-14 is 5730 years. So we can only expect carbon dating to work accurately for fossils as old as 50,000 years, or at a stretch up to 100,000 years with advanced ultra-sensitive methods of laboratory analysis.

That’s the solution. Any fossil artifact older than about 100,000 years cannot be dated using carbon dating.

So either Fitz was wrong about the date of the sand quartz begin over a billion years old, or Bobbi got the dating method Fitz used totally wrong. Since Fitz is a physicist, and Bobbi a field agent and biology undergraduate, the solution is that the scriptwriters for Bobbi were brain dead at the time of typing up this episode.

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