00:00Have you ever wondered how something as rough, grainy and totally opaque you, as deep sand
00:04can turn into the crystal clear glass you are looking through right now.
00:07It feels almost like a magic trick, but today we are going to pull back the curtain on this
00:12incredible transformation.
00:13To start, you might ask what sand is even made of.
00:16Most sand on our beaches is made of silicon dioxide, which you might known as silica.
00:20In its natural state, silica formed teeny hard crystals called quartz.
00:24If sand is just a bunch of solid crystals, why can we not see through the bucket of it?
00:28The reason is that all those teeny grains have rough edges and little defects that reflect
00:32and scatter the light hitting them in every possible direction.
00:35So how do we get those messy grains to cooperate and become transparent?
00:39We have to melt them down.
00:40You might think that sounds easy, but pure silica only melts at a staggering 1700 degrees
00:45celsius, which is hotter than a spacecraft returning to earth.
00:48Since that is way too hot for most women to handle, glass makers add two secret ingredients
00:53called soda ash and limestone.
00:54The soda ash acts like a shortcut to lower the melting point.
00:57While the limestone keeps the finished glass from actually dissolving in water.
01:01Once the heat hits that 1700 degree mark, the solid sand gains lose the rigid structure
01:05and turn into a glowing thick liquid that flows like orange honey.
01:09Now here is where it gets really weird.
01:11When this liquid cools down, it doesn't go back to normal crystal solid.
01:14Instead, the molecules get stuck in a messy disordered state that scientists call an amorphous
01:19solid.
01:19It acts like a solid because it is rigid.
01:21But it has the chaotic internal structure of a liquid.
01:24Because this structure is so uniform on a microscopic level, light can strike the surface without being scattered away.
01:30But wait, you might ask, even if the light is not scattered, why is it not observed by
01:34the atoms like it is in a piece of wood?
01:36To answer that, we have to look inside the atom, which is actually almost empty space.
01:40Imagine an atom is as big as a massive sports stadium.
01:43The nucleus would be a tiny pea in the middle, and the electrons would be like grains of sand
01:47way out in the seats.
01:48There is plenty of room for light to zoom right through without hitting anything.
01:52But in most materials, electrons act like gatekeepers that grab the light energy.
01:55Think of these electrons as people sitting in certain rows of that stadium who want to
01:59jump to a better row.
02:00To make that jump, they need exactly the right amount of energy from a light particle or a photon.
02:05In materials like wood or metal, the rows are close together, so photons, the visible light,
02:09give the electrons just enough energy to jump off, which means the light gets observed or reflected.
02:13But in glass, those rows of sieves are spaced incredibly far apart.
02:17A photon or visible light simply does not have enough tools to keep an electron make that a huge leap,
02:21so the photon just keeps on going right through the atom without being touched.
02:25This is why glass is invisible to our eyes but perfectly solid to our hands.
02:29Interestingly, photons from ultraviolet light actually do have enough energy to be observed by glass,
02:33which is why you generally cannot get a sun turn through a window.
02:36So next time you look through a window or check your phone's screen,
02:39remember that you are looking at sand that has been melted, reshaped,
02:42and frozen into a permanent state of molecular chaos.
02:44hourglass sizes close to the feet.
Comments