# Rapunzel Physics, Rumpelstiltskin Engineering: The Science Behind Fairy Tales – World Science Festival

Wherever the pleasure of Grimm’s Fairy Tales and other folk tales may lie, it’s hardly in the plausibility of the stories, but it’s fun to see how particulars of the fantasy could actually occur in real life. Here are a few instances where fairy tale events don’t require any magic.

Climbing a Tower With Hair (Rapunzel)

If Rapunzel lets down her hair, could a prince really climb that golden stair? In 2011, a group of physics students at the University of Leicester investigated this question for the school’s Journal of Physics Special Topics, which is devoted to applying math and science to creative questions. One of the primary pieces of data needed for this calculation was the ultimate tensile strength of human hair: How much stress it can take while being stretched before breaking. The physicists cited a separate bit of research published in the Journal of Cosmetic Science that found that human hair’s ultimate tensile strength was around 380 Megapascals (MPa), which is stronger than cast iron, aluminum, and copper, but weaker than steel. Still, it seems to be enough for Rapunzel’s visitors to ascend without incident.

Rapunzel’s hair “could support a weight of 27kN, or just over 2750kg [over 6,000 pounds],” the group wrote. “It is, therefore, safe to conclude that Rapunzel’s hair could easily support the weight of a man.”

The real tricky question is whether Rapunzel’s hair could actually reach the ground. Human hair from the head grows at a rate of anywhere between 4-6 inches a year, so, depending on the height of the tower, the prince may have to wait a bit to meet the princess.

Spinning Straw Into Gold (Rumpelstiltskin)

Turning straw or at least certain plants into gold doesn’t require a spinning wheel or making a deal with a freaky little man who’s interested in hiding his name. All you need are the right chemicals.

Plants absorb a lot of material from the ground as they suck up water and nutrients, so if there are precious metals in the soil, they can soak bits of those up too. In 2002, Miguel Yacaman and Jorge Gardea-Torresdey from the University of Texas found a way to extract some of that gold from a variety of plants, including alfalfa, wheat, and oats. But they weren’t looking to mine hidden gold from the ground; the pair’s research focused on using plants to create special tiny particles of gold that can be used in biological research and nanoengineering. After plants have been grown in gold-rich mediums, the scientists can use solvents to dissolve the organic material and leave the gold nanoparticles behind.

Another group led by Chris Anderson at New Zealand’s Massey University has been experimenting with ways to help plants suck up gold—along with other materials like copper, arsenic, and mercury—more easily, in order to clean up contaminated mining sites. Like Yacaman and Gardea-Torresdey, Anderson’s team wasn’t looking to make a fortune off of their work, since the yields of gold are incredibly small for the amount of effort put in. But at least you don’t have to sign away your firstborn to get it.

For more check out the WSF link below

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