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Milk Please

  1. Aug 12, 2008 #1
    Milk Please..!!!!

    Part of my early morning ritual involves making myself a nice cup of coffee.

    I pour my aromatic brew into the cup and then add a little sugar.

    In the process of getting the sugar to dissolve, I give the contents a clockwise stir, turning the teaspoon, (not too vigorously, not to slowly) but just enough to cause a little centrifugal dip in coffee as it turns. (alternately you can say the centrifugal force pushes the coffee slight up the sides of the cup, with the centre of the cup being the lowest point)...I am happy with either...

    Anyway, as this is happening, I take the milk carton, open it, and begin to pour milk in a thin stream directly over the top of the centre of the cup. This I do at a height of about 8 to 10 inches above.

    Then a delightful and to my mind exciting thing happens.

    In the process of pouring the milk into the centre of the cup, it seems to collect not only enough force, so that I can virtually see to the bottom of the cup; but even more wonderfully, a gap of about 3 to 5 millimeters opens up between the descending milk stream and the rotating coffee into which the milk is being poured.

    In due course, it seems to me, that the wall of rotating coffee and milk, actually picks up a bit more rotational speed while the milk pushes down, out and up against the sides.

    Eventually after about half a second or so, the air gap, dividing the stream of milk from the rotating coffee collapses inwards...thus obliterating that wonderful vortexed wall space.

    What I'd like to know, is what is causing the gap between the descending milk stream and the rotating wall of mixing coffee and milk?

    If you don't know what I am describing, go out and give it a shot...

    For me, its one of those everyday mysteries...for which I do not have a full explanation...

    So...please, if you can shed some light on this phenomena, then I am all ears...


  2. jcsd
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