Inspired by Scroge McDuck, of course. We were discussing how you could not swim in gold coins because they stack together and form into a more solid entity, and are not fluid like water. And then we were talking about ball pits and she asked if she had gold marbles in a swimming pool could she swim in those?
I answered no originally but then realized, I don’t know for sure.
In: Physics
Rather unlikely. Gold is pretty dense (19.33 g/cc ie 19 times that of water). So 1000 cc (1 liter) of gold would weigh 19 kg. A cup of gold would weigh approx 11 pounds. If you were submerged in gold marbles by even 1 feet, you’d probably have something like a ton of weight on your body.
The reason why you can move through a ball pit with relative ease is because the balls are hollow and generally extremely light and not dense. Gold is one of the most dense metals we have readily available. If you made them hallow enough to be able to easily move through them they’d likely crush when you touch them because it would be so thin and gold is a very soft metal.
The problem with gold specifically is the density. It’s eight times denser than glass and 19 times denser than water.
You could probably work your way through glass marbles, but gold marbles will collectively weigh many thousands of pounds and you’d struggle to move them by hand at all.
Not answering your question specifically, but your daughter will probably find Mark Rober’s video about [swimming in a hot tub of sand](https://www.youtube.com/watch?v=My4RA5I0FKs&vl=es) absolutely fascinating!
His videos are very child friendly and he explains the physics of what is going on really well.
If the marbles in an irregular pile, then you could, kind of.
But imagine if you had a swimming pool that was, say, exactly 20000 marbles wide and exactly 100000 marbles long. In that case, marbles could settle into perfect rectangular sheets, all lined up just right, and those sheets would be absolutely rigid. You couldn’t move a sheet like that unless you were strong enough to crush glass.
So it matters a lot how organized the marbles are. If they’re piled in every which way, they’d behave more like a fluid. If they formed a big “crystal” of neat vertical and horizontal rows, they’d be much more like a solid and diving into that would equal severe pain.
It would also matter what kind of stroke you used. If you try to kick up and down in marbles, it would be extremely hard to move your legs down into a pile of marble and so not much would happen. But if you stroked across the surface, like a breaststroke, the marbles would have a much easier time flowing horizontally and you’d be able to push off against them.
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