10/16/2013 04:39 pm ET Updated Dec 16, 2013

Soft Matters With Itai Cohen

Okay, I admit it. I'm a sci-fi nerd. Star Trek, Spider-Man, and just about any movie with giant robots blowing things up -- I love them all. But as a physicist and a fan-boy, I visibly cringe when the token scientist is (1) a crazy egomaniac, (2) a socially awkward nerd, or (3) carrying around flasks while wearing a white lab coat. Sure, some folks line up with these stereotypes, but reality is far more interesting...

To give a more authentic view of the contemporary scientist, Katie McGill from the Physics Factor YouTube channel and I are bringing you stories from behind the scenes of physics. We're calling the series "Soft Matters: Talking Physics, Talking Life," and every week over the next several weeks, we'll be showing you what we do, how we do it, and what keeps us going (even when the government is shut down).

In the first episode of our weekly series, Katie sat down and talked with Prof. Itai Cohen at Cornell University's physics department. They chatted about how Itai got involved in research, a bit about what his lab does, and how he spends his weekends. Watch the video, and check below for a no-nonsense science-to-English dictionary.

Science-to-English Dictionary:

Triphenyl phosphite

In addition to the familiar three states of matter -- solid, liquid, and gas -- there are several others we see less frequently in day-to-day life. Triphenyl phosphite is a chemical compound that when supercooled (cool do-it-yourself video here) can transition to some of these exotic states.

Phase transition
Ice melting to water, and water boiling to gas are both examples of phase transitions. Any change from one state of matter to another is also an example.

Brownian motion
The random motion of microscopic particles (watch this Minute Physics video explaining the details and the connection to Albert Einstein!).

Colloidal suspension
A substance containing microscopic particles (1 to 1,000 nanometers in size) mixed into another typically liquid-like substance. A few everyday examples include toothpaste, paint, blood, milk, and hand cream.

Mechanics of wing motions
Itai's lab studies the flight of insects (see here, here, and here).

Mechanics of biological tissues
Itai's lab also studies the mechanics of biological tissues (read more here).

Knee cartilage, energy absorption, and "300 microns, it's all you got!"
Articular cartilage is a "soft" tissue that covers the end of long bones. It's often thought of as a biological "shock absorber," but work coming out of Itai's lab shows that any absorbing properties are localized to the tissue's surface. This region is very thin (300 microns = 0.012 inches), and once it's eroded away, the body can't make more.

This is one of the ways a composite material (like steel reinforced concrete) can fail. Basically, if it takes too much abuse, cracks will grow to form layers, and the layers will eventually separate.

Stokes flow
Try to imagine swimming in a pool of honey -- this is the idea of Stokes flow.

If you record a time-reversible event on video, you can't tell if the movie is played "forwards" or "backwards." As it happens, time reversibility is intimately related with a very important physical law called "the conservation of energy."

Watch Itai and the "Dance of Scales."

Visit the Itai Cohen research group site.

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