The science behind Captain America's shield, The Hulk's anger, and more

Superheroes in comics and movies have powers beyond what we mere humans can dream of — and we're not just talking about looking good in spandex. But could Thor's hammer or Wolverine's claws work in real life? Science has some possible explanations:

Target: Controlling weather, like Thor and Storm

Could we manipulate lightning the way Thor does using his hammer, or control weather like Storm from X-Men? According to Dr. James Kakalios in The Physics of Superheroes, the key ingredient to meteorological mastery would be the ability to alter atmospheric temperature variations at will.

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What does temperature have to do with weather? Everything! Keep in mind that cold air molecules have less energy, while hot air molecules have much more energy, sending them careening around and causing hot air to rise. When hot air meets the colder temperatures at higher altitudes, the air then cools and loses energy; the opposite happens on the ground when cold air collides with the warmer ground. This cycle is called "thermal convection," and having a means to affect this cycle would allow you to control air pressure and humidity.

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By manipulating the temperatures that would allow them to form clouds, Thor and Storm would be able to create localized thunderstorms and thus lightning strikes. However, they would not be able to control the exact point the lightning will strike, as that is dependent on the charge buildup in the ground in that area. DARPA has been investigating the physics behind where thunderbolts hit in order to protect certain places from lightning strikes.

Thermal convection control could also explain both Thor's and Storm's flying abilities: by making the air underneath them hotter and above them colder, they can be wafted into the sky on a bed of warm air.

Target: Flying, like the Falcon

In the recent film Captain America: The Winter Soldier, Sam Wilson flies as The Falcon thanks to artificial glider wings attached to a special jetpack. In reality, jet packs have yet to pass into regular use because of simple logistics: it takes a lot of fuel to propel a human — not a creature optimized for flight — through the air. Most jetpack prototypes can only sustain flight for 30 seconds. (One model in development, the Martin Jetpack, promises longer flight using basically a small jet engine strapped to the pilot's back).

Truly human-powered wings, or "ornithopters," as they're typically called, may fare better if the The Falcon imitated his bird namesake. The Falcon's strap-on glider wings are rigid, like segmented airplane wings, but a bird's wing is constantly changing shape with every upstroke and downstroke, maximizing its flying efficiency.

But mimicking the flexible, precise deformations of a bird wing is a tall order for any engineer. In 2010, Canadian engineer Todd Reichert and his team created the Snowbird, a ornithopter that flaps its carbon fiber/balsa wood. Snowbird is no long-haul flyer; it's record-setting flight lasted just 19.3 seconds. Reichert said in an interview with Popular Mechanics that the Snowbird could probably fly even farther and higher if his team had tried to emulate the complexity of a bird's wing.

"The problem is, in engineering that's not the way to go," Reichert says. "You don't want to say, 'Oh, let's add complexity to get efficiency.'"

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Or you could dispense with wings altogether, like Superman in his first run of comics. He didn't fly so much as "leap tall buildings in a single bound," thanks to Earth's comparatively weak gravity and his superior Kryptonian physique.

Target: Repelling force, like Captain America

Captain America's shield is a versatile thing: able to absorb blows from Thor's hammer without suffering a scratch, able to ricochet around walls and knock out n'er-do-wells. There's no material on Earth yet that can match that kind of performance, and it's just as well; in the Marvel universe, Cap's shield is made from an alien metal called "vibranium," which absorbs sound and vibrations.

But when Thor smashes the shield with his hammer, all that energy has to go somewhere. Kakalios thinks that Captain America's shield may distribute sound waves via the atomic bonds of the vibranium, which the metal might subsequently convert into some sort of optical effect. Since Cap's shield does not appear to emit any light in use, it may be that the vibranium radiates in the infrared portion of the spectrum.

Matt Shipman, a writer for North Carolina State University's science blog The Abstract, raises the possibility that Cap's shield might also function as a combination of a supercapacitor and a battery. Supercapacitors absorb and release energy very quickly — useful for quickly dispersing the force from a blow — while batteries release stored energy at a more measured rate — which might be useful for creating a high-powered boomerang. Those are some pretty powerful little atoms!

"We're all familiar with real-world examples of technology that converts kinetic energy into stored energy, like the flywheel and generator tech that uses the friction from stepping on the brakes in a Prius to charge the car's batteries," Shipman writes. "As is so often the case in comics, there's a kernel of scientific truth here — Cap's shield just takes it one step further."

Target: Channeling anger, like the Hulk

How does getting angry turn Bruce Banner into the Hulk? While we don't recommend exposing yourself to gamma rays, as the origin story goes, it turns out the physiological effects of anger are incredibly powerful. As soon as a stimulus triggers emotion, tension in the body builds and your amgydala starts initiating the "flight or fight" response. This is when the hormones adrenaline and noradrenaline are released from the adrenal glands (which are located right above your kidneys) into your blood. Your breathing rate, heart rate, and blood pressure increase, pupils dilate, and allows blood to flow more freely to the muscles, providing them with increased levels of oxygen so they can contract more easily.

In times of stress, people have been granted an extra burst of strength — perhaps due to adrenaline. There are many stories of a 100-pound mother lifting a truck off of her child in a moment of panic, but adrenaline isn't a wonder-drug. It definitely gives an edge, though, as it did to weightlifter Tom Boyle, who held up a car to save a cyclist trapped underneath. Boyle's previous deadlift record had been 700 pounds, while the car weighed about 3,000 pounds. Scientists think that an adrenaline surge can nudge a person close to the maximum theoretical possible amount of force their muscles can exert.

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Vladimir Zatsiorsky, a Penn State professor of kinesiology, estimated in an interview with Scientific American that most people can reach about 65 percent of their potential in a training session; expert weightlifters can summon 80 percent of that figure. In times of extreme stress — say, an Olympic weightlifting competition, or seeing a biker trapped under a car — people may be able to reach above 90 percent of their physiological maximum capabilities. So adrenaline doesn't really bestow superpowers on us, so much as unlock the superhero inside.

Target: Claws to cut through anything, like wolverine

Wolverine's innate mutant superpower is a superhuman ability to heal and regenerate damaged tissues, which allowed him to survive an intense series of operations that fused a super-strong metal alloy called adamantium to his skeleton. In real life, scientists are looking to enhance our natural healing abilities. One technique involves using material from pig bladders called the extracellular matrix — a kind of biological scaffolding that supports cells, but also contains proteins that can stimulate tissue regeneration.

But if you're looking for adamantium skeleton and claws for yourself, you'd be out of luck — the metal's completely fictional. But materials scientists are working to make harder, more resistant metals, like super-tough aggregated carbon nanorods (ACNR), which are made from compressed "buckyball" carbon molecules and are denser than diamonds. North Carolina State University scientists also made a super-strong form of iron by using nanocrystals of an iron-zirconium alloy, allowing it to withstand temperatures up to 1300 degrees Celsius (2,372 Fahrenheit).