Maggie Koerth-Baker has written a chemistry and combustion rundown of ammonium nitrate, the chemical believed to be behind the devastating blast yesterday in West, TX: “Ammonium nitrate fertilizer isn’t really a dangerous explosive (most of the time)”. Ammonium nitrate, a primary ingredient in synthetic fertilizers, isn’t itself very explosive. Accidents involving it are actually pretty rare, although incidents like the Oklahoma City Federal Building bombing in 1995 have given it quite a reputation. However, like anything, it’s the dose that makes the poison.  When it burns, it creates its own oxygen, which can lead to a runaway fire. In those runaway fires, the chemical can bind together from pellets into a massive plug, allowing it to trap huge amounts of hot gases beneath the weight of burning material. You can guess what happens when hot gases build up with no place to go. More details at Boing Boing. Stay strong, West, TX.
Pop-upView Separately

Maggie Koerth-Baker has written a chemistry and combustion rundown of ammonium nitrate, the chemical believed to be behind the devastating blast yesterday in West, TX: “Ammonium nitrate fertilizer isn’t really a dangerous explosive (most of the time)”.

Ammonium nitrate, a primary ingredient in synthetic fertilizers, isn’t itself very explosive. Accidents involving it are actually pretty rare, although incidents like the Oklahoma City Federal Building bombing in 1995 have given it quite a reputation. However, like anything, it’s the dose that makes the poison. 

When it burns, it creates its own oxygen, which can lead to a runaway fire. In those runaway fires, the chemical can bind together from pellets into a massive plug, allowing it to trap huge amounts of hot gases beneath the weight of burning material. You can guess what happens when hot gases build up with no place to go.

More details at Boing Boing. Stay strong, West, TX.

Source: Boing Boing

Slow Burn

Isn’t watching a match burn in slow motion a hypnotic sight? Want to know what you’re looking at?

For something as ubiquitous as matches, it strikes me that very few people know what goes into creating fire on the end of a stick. Let’s open the book and illuminate the science behind this burning question.

I’ll stop the puns now.

Having a source of fire on demand was not always such a trivial pursuit that we were willing to give things like matches away for free at the Olive Garden hostess stand. As far back as the 6th century A.D. the Chinese were using sulfur-coated sticks to spread fire from camp to camp, because without fire, you died or ate raw food.

Most of what’s in a match today is a chemical called potassium chlorate, which is really just a good source of the oxygen atoms that every flame needs in order to burn. There’s also a good bit of sulfur, which is what’s doing most of the burning and what gives matches their characteristic smell (and why some people keep them in the bathroom), glue, and inert stuff. The “strike” part of the match was added later, when inventors in the 1800’s added a chemical called “white phosphorous”.

White phosphorous is a common explosive that burns super-vigorously when it comes in contact with oxygen under the right conditions, like when a little heat is added. Unfortunately it works a little too well, and it’s also enormously toxic. It was eventually replaced with a less volatile, less toxic form called “red phosphorous” after factory workers began dying left and right.

So what happens when you strike a match?

If you try striking a common match on regular sandpaper, nothing will happen except that you end up with a handfull of toothpicks. The special red sandpaper has a tiny bit of red phosphorous embedded in it, and when you drag the match across it creates heat. If you make enough heat, a wee bit of red phosphorous gets turned into white phosphorous and starts microscopic explosions. Remember the sulfur in the match head? At regular atmospheric oxygen concentrations the sulfur isn’t very flammable. But add some pure oxygen and heat and sulfur goes ballistic. The tiny sparks from the red-to-white phosphorous release oxygen from the potassium chlorate so that the sulfur is able to burn in a high oxygen environment. 

Eventually, the wood catches, and you try to say the alphabet or something before it burns out.

So it’s more than just a cool slow-motion video, it’s a close-up on chemistry!

Big Week for “Synthetic” Biology A jellyfish made of silicone, and a bacterium made in silico Synthetic biology is traditionally thought of as repurposing existing or designing new biological parts to do novel things. But in a larger sense, it can be thought of as the ability to create biological systems outside the limitations of pesky things like global and evolutionary time scales. This week marks two really stunning bio accomplishments, each fitting into their own definition of “synthetic”. Whoa, Jellyman: Cal Tech and Harvard biophysicists announced that they had created a sort of “synthetic jellyfish” this week (pictured above left). By taking thin, carefully designed sheets of silicone and layering rat heart muscle cells over them, they were able to make a bell-shaped living device that pulsed and swam just like the bell of a jellyfish. Heart muscle cells, or cardiomyocytes, naturally grow together in sheets and will automatically “beat” in a petri dish (with the help of a little calcium). If you provide an outside voltage (like a pacemaker) they will beat in unison! The rat-heart-silicone “medusoid” shape contracted, with the beating cells pulling on the silicone substrate just as a jellyfish’s own muscle cells act on its bell to swim.  Of course, this isn’t a real jellyfish, but for extra credit you can read Ferris Jabr’s take on what it would actually take to build one. Byte-size Bio: The other big news this week comes from Stanford and the J. Craig Venter Institute (gracing the cover of Cell this week, above right). Not content with making the world’s first synthetic organism and synthetic genome (Venter’s ambition knows no bounds), they decided to build a computer model of an entire bacterium. Well, mostly. They modeled, on a very general scale, the tiny bacterium Mycoplasma genitalium, which only has 525 genes compared to our ~20,000, and all of its internal processes on 128 computers operating for 10 hours. To complete a single cell division, it required half a gigabyte of data. But you have to be careful before you call this a completely “simulated organism”. Normal cells have many, perhaps hundreds, of just different types of genes, and they interact in myriad ways … we have just begun to scratch the surface of those networks. Just look at how complicated even the tiny changes in a cancer cell can be! By simplifying their model down to 28 minimal systems, their computer program matched the bacterium’s biology as we know it. But a more “realistic” model is going to be exponentially more complicated. Here’s some collected reactions at Tree of Life. But, still … wow! Modern biology has done a very good job at describing the function of individual genes and proteins, but our next chapter lies in how these interactions build into systems. The “-omics” era will be one where we map how the thousands of parts that we are made of combine to make us whole.Simulations like this will be at the leading edge of that era. But we have a long way to go … how many computers would it take to model the trillions of cells in the human body?
Zoom Info
Big Week for “Synthetic” Biology A jellyfish made of silicone, and a bacterium made in silico Synthetic biology is traditionally thought of as repurposing existing or designing new biological parts to do novel things. But in a larger sense, it can be thought of as the ability to create biological systems outside the limitations of pesky things like global and evolutionary time scales. This week marks two really stunning bio accomplishments, each fitting into their own definition of “synthetic”. Whoa, Jellyman: Cal Tech and Harvard biophysicists announced that they had created a sort of “synthetic jellyfish” this week (pictured above left). By taking thin, carefully designed sheets of silicone and layering rat heart muscle cells over them, they were able to make a bell-shaped living device that pulsed and swam just like the bell of a jellyfish. Heart muscle cells, or cardiomyocytes, naturally grow together in sheets and will automatically “beat” in a petri dish (with the help of a little calcium). If you provide an outside voltage (like a pacemaker) they will beat in unison! The rat-heart-silicone “medusoid” shape contracted, with the beating cells pulling on the silicone substrate just as a jellyfish’s own muscle cells act on its bell to swim.  Of course, this isn’t a real jellyfish, but for extra credit you can read Ferris Jabr’s take on what it would actually take to build one. Byte-size Bio: The other big news this week comes from Stanford and the J. Craig Venter Institute (gracing the cover of Cell this week, above right). Not content with making the world’s first synthetic organism and synthetic genome (Venter’s ambition knows no bounds), they decided to build a computer model of an entire bacterium. Well, mostly. They modeled, on a very general scale, the tiny bacterium Mycoplasma genitalium, which only has 525 genes compared to our ~20,000, and all of its internal processes on 128 computers operating for 10 hours. To complete a single cell division, it required half a gigabyte of data. But you have to be careful before you call this a completely “simulated organism”. Normal cells have many, perhaps hundreds, of just different types of genes, and they interact in myriad ways … we have just begun to scratch the surface of those networks. Just look at how complicated even the tiny changes in a cancer cell can be! By simplifying their model down to 28 minimal systems, their computer program matched the bacterium’s biology as we know it. But a more “realistic” model is going to be exponentially more complicated. Here’s some collected reactions at Tree of Life. But, still … wow! Modern biology has done a very good job at describing the function of individual genes and proteins, but our next chapter lies in how these interactions build into systems. The “-omics” era will be one where we map how the thousands of parts that we are made of combine to make us whole.Simulations like this will be at the leading edge of that era. But we have a long way to go … how many computers would it take to model the trillions of cells in the human body?
Zoom Info

Big Week for “Synthetic” Biology

A jellyfish made of silicone, and a bacterium made in silico

Synthetic biology is traditionally thought of as repurposing existing or designing new biological parts to do novel things. But in a larger sense, it can be thought of as the ability to create biological systems outside the limitations of pesky things like global and evolutionary time scales. This week marks two really stunning bio accomplishments, each fitting into their own definition of “synthetic”.

Whoa, Jellyman: Cal Tech and Harvard biophysicists announced that they had created a sort of “synthetic jellyfish” this week (pictured above left). By taking thin, carefully designed sheets of silicone and layering rat heart muscle cells over them, they were able to make a bell-shaped living device that pulsed and swam just like the bell of a jellyfish.

Heart muscle cells, or cardiomyocytes, naturally grow together in sheets and will automatically “beat” in a petri dish (with the help of a little calcium). If you provide an outside voltage (like a pacemaker) they will beat in unison! The rat-heart-silicone “medusoid” shape contracted, with the beating cells pulling on the silicone substrate just as a jellyfish’s own muscle cells act on its bell to swim. 

Of course, this isn’t a real jellyfish, but for extra credit you can read Ferris Jabr’s take on what it would actually take to build one.

Byte-size Bio: The other big news this week comes from Stanford and the J. Craig Venter Institute (gracing the cover of Cell this week, above right). Not content with making the world’s first synthetic organism and synthetic genome (Venter’s ambition knows no bounds), they decided to build a computer model of an entire bacterium. Well, mostly.

They modeled, on a very general scale, the tiny bacterium Mycoplasma genitalium, which only has 525 genes compared to our ~20,000, and all of its internal processes on 128 computers operating for 10 hours. To complete a single cell division, it required half a gigabyte of data. But you have to be careful before you call this a completely “simulated organism”. Normal cells have many, perhaps hundreds, of just different types of genes, and they interact in myriad ways … we have just begun to scratch the surface of those networks. Just look at how complicated even the tiny changes in a cancer cell can be!

By simplifying their model down to 28 minimal systems, their computer program matched the bacterium’s biology as we know it. But a more “realistic” model is going to be exponentially more complicated. Here’s some collected reactions at Tree of Life. But, still … wow!

Modern biology has done a very good job at describing the function of individual genes and proteins, but our next chapter lies in how these interactions build into systems. The “-omics” era will be one where we map how the thousands of parts that we are made of combine to make us whole.Simulations like this will be at the leading edge of that era. But we have a long way to go … how many computers would it take to model the trillions of cells in the human body?

Time Stands Still Tonight’s “leap second” and why the Earth sucks at keeping time If you stand very still tonight, holding your breath in the still of midnight darkness, you’ll hear the sound of all the clocks in the world pausing for one second. Actually, you probably won’t hear anything, but you should know that today will be one second longer than a normal day. Why? When trains began to make long-distance travel possible, with schedules dependable down to the minute, there was a worldwide demand for standardized time. So we got Greenwich Mean Time, which defined the measure of a day as the average time of a single rotation of the Earth from the perspective of one Englishman staring up at the sky in Greenwich. In 1820, this just so happened to be 86,400 seconds, or 24 hours. The problem is that the Earth’s rotation is slowing down, and a “solar day” isn’t exactly 86,400 seconds anymore. The Earth doesn’t care about our time system one bit, apparently. How does that work? The Moon pulls on the Earth due to its own gravity. When that’s combined with the natural gravity of the Earth, we get two “high-tide” bulges on opposite sides of our planet. But the bulges don’t line up perfectly with the equator, and the Moon actually pulls on the ocean enough to create a tiny amount of friction. That friction is slowing our rotation by about 0.002 seconds per day per century. Eventually the Earth and Moon will be “tidally locked” and each will have a constant face to the other (like the Moon does to Earth today). Phil Plait explains this all pretty well here. Moreover, earthquakes and all sorts of other stuff mean that this “slowing” business is also irregular.  Earth sucks as a timepiece. Since the 1970’s, our “official time” has been kept by atomic clocks, accurate to one second every 250 million years. We actually changed the official definition of a second to be based on atoms instead of 1/86,400th of a day. But many traditional clocks, not to mention our bodies, are basing their day on day/night averages, and the atomic clocks are basing it on cesium atoms (far more accurately). The day/night clocks are lagging behind! So on a regular basis, the Time Lords of Earth let the atomic clock time pause for one second to bring them closer to sync. That’s a leap second. If we didn’t do this, and just let the clocks go their separate ways, we might cause serious problems to systems like GPS software that depend on super-super-accurate time-keeping.  So tonight, the official clocks will show 23:59:60 before rolling over to tomorrow, and everything is in its right place. Don’t worry if you forget to sync your watch. You’ll just be a second early everywhere tomorrow. More detailed factoids from Phil Plait at Bad Astronomy.
Pop-upView Separately

Time Stands Still

Tonight’s “leap second” and why the Earth sucks at keeping time

If you stand very still tonight, holding your breath in the still of midnight darkness, you’ll hear the sound of all the clocks in the world pausing for one second. Actually, you probably won’t hear anything, but you should know that today will be one second longer than a normal day. Why?

When trains began to make long-distance travel possible, with schedules dependable down to the minute, there was a worldwide demand for standardized time. So we got Greenwich Mean Time, which defined the measure of a day as the average time of a single rotation of the Earth from the perspective of one Englishman staring up at the sky in Greenwich. In 1820, this just so happened to be 86,400 seconds, or 24 hours.

The problem is that the Earth’s rotation is slowing down, and a “solar day” isn’t exactly 86,400 seconds anymore. The Earth doesn’t care about our time system one bit, apparently.

How does that work? The Moon pulls on the Earth due to its own gravity. When that’s combined with the natural gravity of the Earth, we get two “high-tide” bulges on opposite sides of our planet. But the bulges don’t line up perfectly with the equator, and the Moon actually pulls on the ocean enough to create a tiny amount of friction. That friction is slowing our rotation by about 0.002 seconds per day per century. Eventually the Earth and Moon will be “tidally locked” and each will have a constant face to the other (like the Moon does to Earth today). Phil Plait explains this all pretty well here. Moreover, earthquakes and all sorts of other stuff mean that this “slowing” business is also irregular. 

Earth sucks as a timepiece.

Since the 1970’s, our “official time” has been kept by atomic clocks, accurate to one second every 250 million years. We actually changed the official definition of a second to be based on atoms instead of 1/86,400th of a day. But many traditional clocks, not to mention our bodies, are basing their day on day/night averages, and the atomic clocks are basing it on cesium atoms (far more accurately). The day/night clocks are lagging behind! So on a regular basis, the Time Lords of Earth let the atomic clock time pause for one second to bring them closer to sync. That’s a leap second.

If we didn’t do this, and just let the clocks go their separate ways, we might cause serious problems to systems like GPS software that depend on super-super-accurate time-keeping. 

So tonight, the official clocks will show 23:59:60 before rolling over to tomorrow, and everything is in its right place. Don’t worry if you forget to sync your watch. You’ll just be a second early everywhere tomorrow.

More detailed factoids from Phil Plait at Bad Astronomy.

The Sky Is on Fire! The Atlantic has put together a complete guide to the Northern Lights, chock full of beautiful photographs and videos. From coronal mass ejections to the magnetosphere, there’s a full aesthetic education waiting for you here. Previous drool-inducing aurora videos here and here. (via The Atlantic)
Pop-upView Separately

The Sky Is on Fire!

The Atlantic has put together a complete guide to the Northern Lights, chock full of beautiful photographs and videos. From coronal mass ejections to the magnetosphere, there’s a full aesthetic education waiting for you here.

Previous drool-inducing aurora videos here and here.

(via The Atlantic)

Source: The Atlantic