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In Ant-Man, we see Ant-Man shrink to ant size and then pick up a drop of water as if it were a basketball. The water retains structural integrity even though the bottom of the drop is not supported, and even though the width of the drop relative to ant sized hands looks similar to the width of a basketball relative to human sized hands.

Is this possible? What are the physics of this?

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At that size, the effect of surface tension becomes so strong that you can almost treat the drop of water as a bag of water. According to this video from V Sauce, if you were the size of an ant, water would be 21,000 times thicker than it seems to us at normal size. The same phenomenon allows ants to walk on water:

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Or carry droplets of water (thanks to Hypnosifl for this picture):

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And allows some spiders to wear incredibly stylish water droplet hats:

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In addition to the effects of surface tension, it appears that the outer shell of an ant, called a "cuticle", is naturally hydrophobic (i.e., water-repellent), which would make it even easier for an ant to "hold" a droplet of water. If you find a "raft" of ants (which occur when a colony is flooded), you can push it down as hard as you like, but it will keep bobbing back up to the surface, because their hydrophobic shells just refuse to stay down:

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The combined effects of surface tension and hydrophobic cuticles allow ants to survive underwater for as long as 2 weeks by breathing air trapped in tiny bubbles around their bodies:

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The incredible strength of the surface tension of water isn't as familiar to us as it might be to tiny creatures, but the same dynamic is at work when small objects with little or no water displacement float, or when you overfill a glass of water and this happens:

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    @WadCheber To all spider-lovers (arachnophiles) I recommend Eric Frank Russell's essay "A Many Legged Thing" about a friendly spider named Alfred. Unfortunately, it does not seem to have been reprinted; as far as I know, it is only to be found on pages 116-119 of the November 1959 Fantastic Universe. The opening paragraph: "He joined the family uninvited. He was short on looks but long on charm and had the fixed idea that love is a many-legged thing." – user14111 Jul 24 '15 at 0:10
  • @CodeMed - The same idea is at work. Here's a good video of an ant drinking a drop of water: youtube.com/watch?v=qSoiljP54-4 – Wad Cheber Aug 15 '15 at 19:50
  • Got curious about the droplet hat...it seems spiders wear it to cool themselves in hotter days. Interesting. – Rui F Ribeiro Feb 14 '17 at 4:29
  • @JakeGould M'spider – tobiasvl Mar 12 '17 at 21:42
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Surface tension is the answer as shown in Wad Cheber's answer. To add to his excellent explanation, you can see another example of ants using surface tension to their (and Ant Man's) advantage when they are making a raft and

Ant Man is riding the raft of ants while breaking into the building through the water pipes.

This video showcases a real life example: http://video.nationalgeographic.com/video/weirdest-fire-ant-raft

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    Awesome answer - I don't know if it is strictly relevant, but it might be worth mentioning that the ants at the bottom of a raft can breathe because surface tension wraps them in bubbles of air. When the bubbles run out, they shift positions. – Wad Cheber Jul 23 '15 at 23:39
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    Here's a good picture of an ant with bubbles: antlab.gatech.edu/antlab/Water_Repellency_files/5-BC2G7323.jpg – Wad Cheber Jul 23 '15 at 23:41
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    @WadCheber Haha, that's awesome. I didn't know that, thanks for mentioning it. – kjw Jul 23 '15 at 23:41
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    I just found out that ants' exoskeletons are also water repellent, which makes it easier for them to float. – Wad Cheber Jul 23 '15 at 23:43

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