Space Smell, Spectroscopy and Curious Science: The Rest Is Science investigates astrochemistry and playful physics

The Rest Is Science dives into big questions and playful experiments, starting with Megan’s space smell debate and two leading theories for the distinctive scent reported by astronauts. The episode then ventures into how spectroscopy identifies molecules in distant space, including ethyl formate, the raspberry-like compound found in Sagittarius B2, and discusses debated signs on Venus. Interwoven are explorations of naked mole rats and cancer research, the nature of light and spectral lines, and a series of thought experiments from how many times you can fold gum to the smallest unit of chocolate. Throughout, the hosts blend curiosity with accessible, sometimes humorous science, ending with personal stories about a book on evolution and reflections on science and belief.

Space smells and astrochemistry

The episode opens with a viewer question about whether space has a smell. The hosts explain that in a true vacuum there is no odor, yet astronauts report a distinct scent after spacewalks, described as metallic, burnt, or like gunpowder. Two leading hypotheses are discussed: one attributing the smell to polycyclic aromatic hydrocarbons PAHs carried by dying stars, which cling to spacecraft surfaces; the other to ozone formed during cabin repressurization when oxygen atoms react with fresh oxygen. The discussion links to broader astrochemical phenomena and the idea that even odors help us infer conditions in distant environments.

Spectroscopy and cosmic molecules

The conversation moves to spectroscopy, outlining how light analysis revealed hydrogen in the Sun and enabled a method to deduce the Sun’s composition. The host explains how spectroscopy detects molecules in space, including ethyl formate, which gives raspberries their aroma, and how this relates to the ‘scent’ of the Milky Way. The discussion also touches on phosphine signals in Venus’s atmosphere and the controversy surrounding their interpretation, highlighting how spectroscopy informs our understanding of planetary atmospheres and potential life-supporting environments. A nostalgic note recalls a curiosity box with a DIY spectroscope, illustrating how spectral lines connect Earth and space.

From space to Earth: evolution, science and curiosity-led research

Interlaced with space topics are segments on cancer research inspired by naked mole rats, emphasizing curiosity-led science and its long arc from basic biology to clinical advances. The narrative explains how fundamental discoveries in cell division and cyclins emerged from model organisms like yeast and sea urchins, ultimately guiding cancer therapies. The segment underscores the role of public science funding and organizations that support exploratory research, illustrating how small, curious observations can reshape our understanding of health and disease.

Wordplay, mathematics and practical thought experiments

The hosts then pivot to questions about the origins of even and odd numbers, discussing possible etymologies and metalinguistic ideas such as autological words. They explore paradoxes like the Ghreli-Nelson paradox and touch on the classic language of logic in mathematics. The discussion then turns to physical mini-experiments and thought experiments about folding chewing gum, estimating the maximum number of folds before layer thickness reaches molecular scales, followed by a debate on the smallest chocolate piece that remains chocolate, given molecular diversity and sensory thresholds. The segment blends poetry, philosophy and practical science in a way that invites readers to probe everyday phenomena with a scientific lens.

Personal stories and poetic science wrap-up

The episode closes with candid anecdotes about carrying a prairie dog stool sample and a counterfeit penny, using these curiosities to reflect on the human side of science, creativity, and the boundaries of novelty. A recurring theme is the tension between belief and evidence in a religious household, and how science and faith can coexist. The hosts invite questions and stories from listeners, reaffirming their mission to make credible science accessible while maintaining a thoughtful, open-minded approach.