In chapter 10 Krauss says that neutrons
... make up most of the mass of heavier nuclei and thus most of the mass in our bodies.This struck me as odd, because hydrogen has no neutrons and most of our body is made of water i.e. most of the atoms in our bodies are hydrogen. Sure, all other elements in our bodies have a ratio neutrons to protons is greater than one. But I wondered, which effect is larger? The extra neutrons from heavier, rarer elements, or the lack of neutrons from the most abundant element?
I won't keep you in suspense: he got it wrong. Protons win the popular vote for king of the nucleons. But it's a close race!
|Element||Abundance||Z||Average N||N:Z Ratio||Protons||Neutrons|
I started by finding the relative abundance by weight of different elements in the human body. Here you can see why the race is so close. Most of the atoms in your body are hydrogen but these atoms are so light that by weight they constitute less than 10% of your body mass.
Also, while every other element has an N:Z (neutron-to-proton) ratio greater than one, thy are all pretty darn close to one so the effect size is small. I was as generous as possible and assumed trace elements were all Lead-208, which has the highest N:Z ratio of stable isotope.
I think the moral of the story is to remember that nature can get complicated. We don't want to jump to a conclusion given one reasonable-sounding argument. Sometimes we have to work the problem all the way out to find the answer.
Or maybe Lawrence Krauss is prejudice against hydrogen?