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Posts Tagged ‘lightning’

I’ve been reading a new book — an old book really: From Raindrops to Volcanoes by Duncan Blanchard, first published in 1967 and presently being reprinted by Dover. It’s a kind of personal journal of Blanchard’s scientific adventures going from the study of how raindrops generate bubbles in the sea, to the way that these bubbles break and send tiny droplets into the air, to the possible relationship between these droplets and atmospheric charge, to the question of how undersea volcanoes send charges into the atmosphere.

This is the kind of book that shows you how scientists really think: An idea forms; in the course of checking that idea, other thoughts form and other experiments suggest still further avenues of thought. Along the way, other people have similar questions and sometimes more ingenious exercises to test them, and then, charmingly, a visit to the library unearths the works of men who raised these questions hundreds of years ago and made their own guesses, wise or foolish.

So, when a drop causes a bubble, and the breaking of the bubble causes the forceful ejection of new and incredibly tiny droplets into the air, how fast do you suppose that ejection really starts them off? It has to have some momentum because the air is quite thick compared to these tiny droplets and to get them up above the sea requires considerable force… The large ones, of course, we actually see; they might be traveling as fast as we swing our arms, and that can’t be much more than a few miles an hour, the speed at which we walk and swing our arms, right?

But would you believe 180 miles an hour for the little ones? No way! Please read his book and explain to me what he did wrong; there must be something. I didn’t follow every equation, I confess.

Actually, I am sure he was careful; and even though there are some math parts that will not catch everyone’s attention, he does give amazingly clear explanations of his work; it’s not just answers, but how he got there. He has the heart of a teacher; he wants to share his fascination with the physical world, all full of surprises.

Volcanic lightning from Chaiten Volcano May 2008

Here is an image of volcanic lightning from another source. It’s the Chaiten Volcano in Chili, which erupted May of 2008. Notice that the cloud is black and smoky, not grey like a rain cloud. The picture is from a news outlet.

 

 

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Sam kindly lent me his library copy of William Rankin’s amazing account of ejecting from a jet into a thunderstorm. It is just as amazing as the title suggests, and it is a true story. Chapters 11-14 are the account of the ejection, the free fall, the thunderstorm, and his rescue. Here’s a bit about thunder:

Throughout the time I spent in the storm, the booming claps of thunder were not auditory sensations; they were unbearable physical experiences — every bone and muscle responded quiveringly to the crash. I didn’t hear the thunder, I felt it…

After each flash of lightning, everything turned completely black. I was lost in a pool of ink. During the intense brilliant light, when bolts shot by, the clouds seemed to boil around me, sending up huge vaporous balls of grayish cotton. Even when I kept my eyes closed the lightning had a blinding effect.

It’s an interesting description of the effect of lightning within a cloud. That’s something we don’t think about — we know that the heat of a bolt will rip along a tree trunk, and we know that many bolts of lightning go from cloud to cloud, but we don’t consider that within the cloud also, such a blast of heat must make the vapors boil.

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