I honestly don’t know the exact name of that thing. You guys can google it to see the image. Basically, it is a transparent water tank. In the side of it, there is an opening with a smaller tank attached to the main tank where you can put your hand inside to touch the water. What i don’t understand is that: the water of the big tank is at much higher height compared to the small tank. Yet the water doesn’t just flow out. I also can put my hand inside the big tank through that opening, and there is no transparent barrier between the two. It very strange
When you suck a drink through a straw, your suction isn’t pulling the drink up the straw. Your suction creates a low pressure zone in your mouth and regular atmospheric pressure (that is pressing on every part of you but you don’t notice it) is pressing down on the beverage in the cup and forcing it up the straw to equalize the pressure. If the cup were sealed completely, no matter how hard you sucked on the straw, no water would come out as the vacuum you’re creating inside the sealed cup is greater than your muscles.
The aquarium is sealed and there is minimal air at the top of the sealed tank so the weight of the water wanting to overflow the smaller cube is overpowered by the vacuum created as gravity pulls it down. If someone shoved a hose in the opening and directed it up (please don’t do this), the water would come gushing out because air could replace it at the top of the aquarium.