Summary
Overview
Hannah Fry and Michael Stevens explore fascinating questions about space, smell, numbers, and personal discoveries. They discuss the scent of space as reported by astronauts, the mathematical paradoxes of autological words, the molecular limits of chocolate, and Michael shares his childhood book 'Evolution the Lie,' reflecting on the intersection of science and religion. The episode blends rigorous scientific inquiry with personal storytelling and philosophical reflection.
The Smell of Space and the Universe
The hosts tackle a listener question about whether space has a smell. While deep space as a vacuum has no odor, astronauts consistently report a distinctive metallic, burnt smell after spacewalks. Scientists theorize this comes from either polycyclic aromatic hydrocarbons from dying stars or rapid ozone formation when oxygen atoms recombine in the airlock. Using spectroscopy, scientists have also detected familiar odors throughout the universe, including ethyl formate in the Milky Way's dust clouds, which smells like raspberries and rum.
- In deep space vacuum there is no smell, but astronauts report distinctive odors after spacewalks - described as burnt steak, hot metal, gunpowder, or a sweet metallic sensation
- Two theories explain the smell: polycyclic aromatic hydrocarbons (PAHs) from dying stars, or ozone created when stripped oxygen atoms recombine with breathable air in the airlock
- Using spectroscopy, scientists detected ethyl formate at the edge of the Milky Way - the same compound that gives raspberries their smell, meaning the Milky Way smells like a raspberry daiquiri
- Controversial 2020 findings suggested phosphine in Venus's atmosphere - a compound found in penguin poop that's extremely difficult to make naturally
" When you're smelling a hamburger, you are effectively smelling the same compounds that drift around between the stars. "
" The scent of the Milky Way smells like a raspberry daiquiri. "
Even, Odd, and the Grelling-Nelson Paradox
A listener asks about the origins of even and odd numbers and why the words themselves have matching properties. The word 'odd' likely comes from Old Norse describing a sharp point or triangle - the third item that breaks symmetry. This leads to a discussion of autological words (words that describe themselves) versus heterological words (words that don't), culminating in the mind-bending Grelling-Nelson paradox about whether the word 'heterological' is itself heterological.
- The word 'odd' may come from Old Norse meaning a point or sharp edge, possibly originating from the idea of a triangle - when a third person joins two others, creating asymmetry
- Autological words describe themselves (like 'pronounceable' or 'pentasyllabic'), while heterological words don't (like 'long' or 'hyphenated')
- The Grelling-Nelson paradox: if 'heterological' is heterological, it describes itself, so it isn't heterological; but if it isn't heterological, it must describe itself, so it is heterological
" Two people are going to have to talk to each other. But then you bring in a third. And now the voting is different. You can't have an even split. And that third person forms a triangle. "
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