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Hank: Happy end of 2015! I hope it was a good year for you! Because it was definitely a good year for science. At the end of each year, we here at SciShow like to look back and celebrate the year’s science superlatives: what scientists did or discovered that was the most, the best, the awesomest that the world has ever seen.

And there were a lot of amazing developments in science this year, but one of our favorites was the discovery of the strongest biological material on Earth. No, not spider silk. We used to think it was spider silk. But it turns out that the tiny teeth of the common limpet -- an aquatic snail found in rock pools around the world -- are even stronger. The kind of strength we’re talking about here is tensile strength. That’s a measure of how much stress a material can withstand being pulled or stretched before it breaks. It’s typically measured in pascals (Pa). And the strongest spider silk in the world has a tensile strength of about four billion pascals. But British engineers found, this year, that limpet teeth have a strength of about five billion pascals.

Why? Well, limpet teeth contain goethite, a crystalline form of iron, oxygen, and hydrogen. And goethite itself isn’t rare. It’s probably in the dirt outside your house. But as a limpet grows, goethite forms into especially compact, highly resilient, curved filaments that make it stronger than anything else in nature (that we know of). The researchers say we can use this discovery to make everything from ship hulls to airplanes to racing cars stronger and more durable.

Now, what about a superlative for something that you’d assume never changes? Like the speed of light? Yeah, you would think that light always travels at... the speed of light: about three hundred million meters per second. But that’s not actually true: light travels slower when it’s passing through a transparent medium, like air, or glass, or water. Light only travels at “the speed of light” in a vacuum. So, photons of light slow down when they’re passing through a medium, but as soon as they return to a vacuum, they zoom right back up to their natural speed limit.

But this year, scientists did something they’ve never done before: they slowed down light, and made it stay slow, even in a vacuum. They created the slowest light ever measured, forming particles of light that can no longer reach light speed. They did this by passing single photons of light through a special mask made of liquid crystals. The crystals were transparent, so they let light through. But they were arranged into a tiny bullseye pattern. So the photons passed through it lengthwise, through one band of crystals, then into empty space, and then into crystals again.

This not only slowed the photons down, it actually changed the shape of the photons themselves. And scientists then raced one of these deformed photons that had gone through the liquid crystal pattern, against a normal, unshaped photon. And even though both photons were moving through the same medium during the race, they crossed the finish line at different times. The shaped photon lost, every time. Not by a whole lot: just a few millionths of a meter. But it was slower. The idea that some photons can be slower than others is a totally new idea in science. And right now, we don’t really know what to DO with that information. But in the future, this could make some very interesting things possible, like in communication and optics.

So that’s a new slow. Now let’s talk about a new fast. If you want to look at something really, really small - like something a million times smaller than the width of a human hair, like the individual bonds between atoms - you’re going to need an atomic force microscope, or AFM. And unlike the microscope you probably used in school, AFMs don’t use lenses, or light.

Instead, they use a tiny needle, called a probe, that skims across the surface of whatever you want to look at, and then creates a picture, kind of like a topographical map. But this process is really slow, as you might expect. The probe has to scan the sample line by line, and getting a complete picture of something even a few microns across can take ten minutes. And even then, it only works if your sample is just sitting there. But what if you want to watch something that’s moving, like a chemical reaction taking place at the atomic level? Well, you couldn’t.

This was a huge problem for chemistry, and we needed some huge nerds to solve it. Luckily, engineers at MIT developed a new atomic force microscope that’s the fastest microscope of its kind in the world. It's 2,000 times faster than existing AFMs, able to take real-time scans of things on the atomic level, at a rate of about ten frames per second. It can do this because, instead of just using one probe, it has multiple probes of different sizes. The bigger probes can scan larger surface areas, while the smaller ones move faster and scan very small details. Then all of the probes scan at once, to create a composite image from all the data.

Amazing as it sounds, until now, pretty much everything we knew about what goes on when things change at the atomic level has just been theory, or inference. But now, for the first time, in 2015, we can watch it happen. So thank you limpets. Thank you, deformed photons. Thank you, atomic force microscopes, for an awesome 2015.   And thank you, for watching SciShow, which was brought to you by our patrons on Patreon! If you want to help support this show, you can go to patreon.com/scishow. And don’t forget to go to youtube.com/scishow and subscribe!