WHICH TANK FILLS FIRST? ft. Simone Giertz

The entire reason that these memes *ARE* memes is because there is a small/subtle degree of ambiguity.  That stirs up controversy - causes protracted conversations and the meme is spread to more people.  In this case, the clearest ambiguity is around the term "FULL".  If "full" means "kinda full to close to the top" - then 3 wins.  But if it means "absolutely to the top" then depending on whether you can neglect the flow rates of the pipes, etc - then it's a tie between 3 and 4...and if you don't neglect that, then it's 3 again.  Of course if the flow rate through the pipes is substantially less than the input - then 1 fills up first - or the race between 3 and 4 becomes unequal.The point is that the question is carefully framed for ambiguity - and that sparks controversy and spreads the meme.   It was exactly the same with "Airplane on a treadmill" and "What color is the dress?" - they ALL depend critically on some ambiguity in the wording.   What color were the lights in the room where the dress was photographed?  What camera was used - and with what settings?  Are we talking "diffuse" color or "specular" color - and is the dress a lambertian reflector?  Every single time one of these annoying memes shows up - it's 100% down to the unspoken conditions.   The most viral memes are those where the average person DOESN'T consider things like the flow rate into tank #1 versus the diameter of the pipes between the tanks.   This is left to our imaginations - and some people imagine fast water flow and others slow.  Some people interpret "full" in different ways.   Ultimately, the answer to the question posed is 100% all about human nature and 0% due to physics.