Oil and water don’t mix: left alone, oil drops drift up, touch, and coalesce back into a single slick. An emulsion — mayonnaise, milk, vinaigrette — is oil broken into tiny droplets that stay broken.
Whisking supplies the shear that tears big drops into small ones. But small drops have far more surface, and every fresh surface wants to merge again. An emulsion is a fight between shear making droplets and coalescence merging them.
The referee is the emulsifier — egg yolk’s lecithin. Its molecules coat each droplet, and once surfactant coverage is high enough, coated drops bounce off instead of fusing. Coverage also lowers the interfacial tension, so the same whisk makes even finer drops.
Whisk hard with no emulsifier and you’ll watch it break: new surface outruns the surfactant, coverage collapses, and the oil floods back to a slick. Enough coverage is what makes mayonnaise hold.
Something in the simulation stopped unexpectedly — the lesson continues without it. Nothing you did was wrong; you can move on.