The Weird Connection Between Saliva and Quantum Physics

Summary by Krater

This video explains the physics of how liquid streams break up into droplets via Rayleigh-Plateau instability, exploring how surface tension and internal molecular forces interact in water, saliva, polyethylene glycol, spider web glue, and Bose-Einstein condensates.

From the video

Answers: Why do liquid streams break up into droplets?

• Rayleigh-Plateau instability
• surface tension in liquids
• viscoelastic polymers
• spider orb web glue physics
• quantum liquid filaments

What it concludes

• Liquids want to reduce their surface area to minimize surface tension at the air-liquid interface.
• Rayleigh-Plateau instability occurs when the ripple wavelength is equal to the cylinder circumference, causing liquid streams to spontaneously form droplets.
• Viscoelastic polymers like saliva, PEG, and spider glue have internal elastic forces that stretch out and resist rapid collapse, slowing down thinning into droplets.
• Spider orb-web glue uses Rayleigh-Plateau instability to turn silk-coating liquid cylinders into regularly spaced droplets without needing thousands of microscopic placements.
• Bose-Einstein condensates at near absolute zero can form quantum liquid filaments that undergo the same Rayleigh-Plateau instability as ordinary liquids.