Another tornado MADE OF FIRE! Waiting now for tornado made of locusts.

The entire universe in blog form
Aug. 30 2010 12:30 PM

Another tornado MADE OF FIRE! Waiting now for tornado made of locusts.

When I posted the awesome video of a fire tornado last week, I had only heard rumors of such things. Apparently, they're more common than I thought.

Here's another amazing video, and this one is even better: it's longer, and you can see the rotating smoke cloud around the column of fire!

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

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This really is a fantastic demonstration of how microscale weather works. Imagine: a fire starts. As the air is heated above the fire, it rises, and the upward motion can be very strong. This leaves a lower pressure spot at the fire, and the air from outside the fire rushes in to fill the gap. The air is very turbulent, and as the inward-moving air from one side hits air coming in from the other, swirls can form. These get amplified by the constant gale of air, and rotation on a larger scale can get started and sustained. The whirlwind gets pumped by the hot air rising, and the next thing you know you've got a full-blown tornado of fire. Watch the video; see how the fire tornado is narrow and well-focused, but the air outside it is rotating more slowly? That's an outcome of a law of physics called the conservation of angular momentum: if you take something that's spinning and shrink it, the rotation rate will increase. You've seen this a bazillion times; figure skaters start spinning, then draw their arms in. Their decreased radius increases their spin, sometimes very dramatically. Water draining out of a bathtub does the same thing, too.

We see it in astronomy all the time too: massive stars undergo core collapse at the ends of their lives. The core shrinks so much the spin rate can go up vastly, and we're left with collapsed neutron stars -- mind-numbingly über-dense objects with the mass of the Sun compressed into a ball only a few kilometers across, and they're spinning quite literally a thousand times per second: faster than the blades of a kitchen blender.

Angular momentum is a powerful, powerful thing. And it's also beautiful. On scales as titanic as an octillion tons of star matter collapsing to form a weird quantum mechanical fluid, down to an almost supernaturally awe-inspiring column of fire, physics is everywhere, and it's an astonishing thing to watch.

Tip o' the fireman's helmet to Dave Mosher.