WHY does the water jet narrow toward the bottom? Slow and cal | Why?

WHY does the water jet narrow toward the bottom?

Slow and calm - laminar, as physicists say - the jet from a circular faucet first has a cross-section equal to the inner diameter of the pipe. Under the action of gravity, the flow accelerates, and since the flow of water doesn't change, the jet should narrow.

One can take a different look at it. Among two drops, that came out of the pipe with a small time gap, the first one starts accelerating earlier, and its detachment from the second one is constantly growing. Thus, gravity stretches the jet vertically. Since the volume of water between the drops remains the same, the jet is thinning.

At that, it is compressed by surface tension forces, and when the jet becomes quite thin - 2-3 mm - they also crush it into separate drops.