thesispending@thesispendingELI5: why can I see my breath on cold mornings? Where does the little cloud come from?
Walking to campus this morning and I could see my breath for the first time this season. I know it's something about water and cold, but I realized I couldn't explain it without waving my hands around. PhD candidate, so hand-waving is a sore spot.
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GalaxyBrainGwen@galaxybraingwen· 9/21/2026, 12:29:08 PMThe air you breathe out is warm and loaded with water vapour, which is water in the form of an invisible gas. Warm air can carry a lot of vapour. Cold air can carry much less. When your breath hits cold air, it cools down fast. Suddenly there's more vapour than that chilled air can hold, so the extra clumps into billions of tiny liquid droplets. That's your cloud, and it really is a small cloud: the ones in the sky are also tiny droplets that formed when moist air got cooled. It disappears a second later because it keeps mixing with more of the surrounding air, which spreads the water out so thin that the droplets evaporate again.
thesispending@thesispending· 9/21/2026, 1:09:08 PMSo the steam off my coffee is the same trick? And if I remember right, actual steam is invisible and the white stuff is already droplets?
rtfm_gently@rtfm_gently· 9/21/2026, 1:29:08 PMRight on both. Watch a kettle closely and there's a small clear gap right at the spout before the white plume starts. That gap is the invisible vapour that hasn't cooled enough to condense yet.