Friday, February 26, 2010

Physics Problem of the Week

So... I'm reading the current Dick Tracy comic strip (online, of course), and lo and behold, a physics problem comes up. The current story line, which has been running since Thanksgiving, involves a Stradivarius violin that's been loaded with plastic explosive, rigged to go off when the violinist hits a high C (most likely a C-4), and sent to a fancy reception at a foreign embassy. We don't yet know why somebody's going to such great lengths, or such a roundabout plot, to assassinate the ambassador (perhaps that will be revealed later), but we do know that as of last Saturday, Tracy had grabbed the Strad and chucked it into the swimming pool seconds before it went off with (and I quote) an enormous "FLOOOOM!"

In the wake of the blast, several questions came up:
  • Why would someone pay two million bucks for a Stradivarius, when a cheap high-school orchestra violin would have exploded just as well?
  • Why is there and embassy in Naperville?
  • What are those two big hand-like things sticking out of the pool during the "FLOOOOM!"? (Could the explosion have aroused the Ancient Slime Monster foretold by Mayan prophecy?)
  • Why is there a swimming pool in the embassy's formal dining room?
Of course, these are questions that can't be answered by physics (or any science, for that matter). But two other questions came up, questions that are amenable to science, and they center around what happened to the water:
  • Since the water seems to have simply disappeared in later strips, did the explosion vaporize it?
  • Or, if the explosive lacked the ooomph (that's the technical term) to vaporize the water, could it at least actually blow the water out of the pool.
These questions we can answer with a little chemistry and physics.

A quick trip to the internet divulged two important bits of information: C4 plastic explosive is mostly something called RDX, with a chemical formula of C3H6N6O6. It's a pretty interesting molecule, with a structure kind of like a snowflake--an inner hexagonal ring of alternating carbon and nitrogen atoms, and branches off that ring. Each carbon binds to two hydrogen atoms (that's pretty standard, like gasoline), and each of the three nitrogens is hooked up to an NO2 group, which is sort of a molecular menage a trois, in which the two oxygen atoms are hooked up with the nitrogen for now, but would happily take a better offer if one came along. The RDX molecule is energetic and only kind of stable, and when it breaks down into N2, H2O, CO2 and some loose carbon soot, it gives off a lot of energy. How much? Well, according to a paper I found on the internet, where the author analyzed those complicated "resonance" bonds in the NO2 groups, RDX liberates 10 million joules of energy per mole when it goes off.

According to another website on military stuff, the "standard" brick of C4 explosive is half a kilogram, and is about 90 percent RDX (the rest is binders and stuff). So, given the molar mass of RDX is 222g, that brick is just about exactly two moles... so when the Stradivarius goes off, 20 million joules get released.

Is that enough to vaporize the water in the pool? Not even close. It takes a lot of energy to boil water--something over 2 million joules per kilogram, so the 20 million joules released by the explosive in the Strad would only boil away about ten liters. Barely enough energy to boil the champagne.

But is it enough to empty the pool? Well, let's look at the pool and make some estimates. Looks to be about ten meters in diameter, and let's assume it's about two meters deep. That gives a volume of 25 times pi times 2, or 157 cubic meters. A cubic meter is 1000 liters, or 1000 kilograms, so the mass of water in the pool is 157,000 kilograms. So, when the Strad goes "FLOOOOM!", we've got 20 million joules acting on 157,000 kilograms. From these numbers, and the formulas for kinetic and gravitational energy, we can figure out how fast the water will be flung out of the pool, and how high it will splash.

First, how fast: the formula is Ek=0.5mV**2 (sorry, but Blogger won't typeset exponents). Rearranging the terms to solve for velocity, we get V=sqrt(2Ek/m), and if we plug in the numbers that's V=sqrt(2*20,000,000/157,000)=sqrt(255)=16 meters per second, which is about 35 miles an hour.

Second, how high: the formula is Eg=mgh, where g=the acceleration of gravity, 9.8 m/sec**2. Rearranging the terms to solve for height, we get h=Eg/(mg), and plugging in the numbers gives us h=20,000,000/(9.8*157,000)=20,000,000/1,530,000=13.1 meters, or about 43 feet. That's a pretty good lift, but... it's been three days since the Strad went off, and the water still hasn't come back down. Time must work differently in the Dick Tracy universe... but that's relativity, and that's a problem for another day.

Monday, February 22, 2010

Medieval Underwear, and Other Topics of Research

I spent the better part of an hour yesterday wandering about the internet in search of information about what forms of underwear were worn in various periods of history. No, I'm not a pervert; it was research for a book I'm working on.

My approach to research, at least in my first novel The Last Protector (available for purchase; just click one of those links to the right) is a simple one: I just make stuff up. It's an approach that works pretty well in fantasy and SF (not so well in historical fiction, of course, which is why I avoid that genre). I'll recommend it without reservation to any aspiring authors who might be reading this.

Alas, I don't always take my own advice. I'm currently working on a story set in a place that the inhabitants at least believe is Camelot. Which means I have to do some research. Not a lot, since the first thing you discover when researching the "historical Camelot" is that there is no such thing. Or there are dozens of them, which is the same as saying there aren't any. Nobody really knows if there was a King Arthur, let alone when or where he might have reigned. So researching in that area was pretty easy; I listed a dozen or so popular options and then picked the one that best fit the rest of my story (which, in this case, meant the one where the supposed ruins of Camelot were such a minor archaeological site that the Ministry of Transport built a four-lane motorway right over them).

Other research was a bit more daunting. At one point, I found myself wondering if there was any chance that a set of bagpipes that had been put away for twenty-five (in a cool, dark, dry place, with the reeds sealed in a baby-food jar) could still be revived and played. Luckily, there's a huge group of experts out on the Bob Dunsdire piping forum. Not only did they tell me just how the pipes would have to be stored (and whether the bag seasoning would survive that long); they also gave me loads of insight into how pipes changed over that twenty-five years (mid 1970s to the beginning of the new millennium). It was a most profitable, and most enjoyable discussion.

Sometimes, research results just dropped into my lap, courtesy of Mother Nature and Global Climate Change (tm Al Gore Enterprises): while we may argue about the precise location of Camelot in both space and time, we do tend to agree it was somewhere in England. And I needed to know a bit about winter weather in England--how cold does it get, for how long, and how much snow might be expected. In particular, do they have anything as brutal as a Chicago winter? Fortunately, Mother Nature obliged with a once-in-a-lifetime cold snap and winter storm, so I was able to get my characterization of "extreme winter weather" from the BBC's daily reports (and no, it's not up to Chicago standards--ten centimeters of snow, about four inches, brought things to a halt; and there were warnings of severe cold, which meant sustained temperatures below zero degrees C). Thanks, Ma Nature... and to those of you in England who suffered through the storms, sorry 'bout that. We do apologize for any inconvenience.

And then there's the matter of those Arthurian undies. Suffice it to say that I found about as much reliable information about what Guinivere wore under her royal gowns as I did about when, where and whether Camelot actually existed. In other words, a lot of speculation, a lot of inference, and very little actual historical fact. It appears they didn't publish the Victoria's Secret catalog in pre-Victorian times. Sigh... a lot of work for what will probably end up being all of two or three paragraphs. I think I'll just go back to my primary research technique and just make something up.

Or I could just put everybody in kilts. That would solve the underwear problem, right?

Tuesday, February 9, 2010

We're Done. Who's Next?

Last week the Obama administration announced the official end of the US manned space program. The "Constellation" project, which had just barely gotten off the ground with a fairly pointless four-fifths-stage rocket test last month, is now dead. When the last shuttle flight comes back down, sometime late this year, the United States is officially ending its career as a space-faring nation. Americans may still travel to the space station, but they'll do so as paying passengers aboard Russian Soyuz craft. More ambitious stuff, like returning to the moon or going on to Mars... forget it. We're done.

So, since the US has abandoned space, who might pick it up? Who's going to press on to the next lunar landing, the trip to Mars, the journeys to find out if anything lives in the vast ocean under the ice of Saturn's moon Enceladus? If it ain't us, then who?

Will the Private Sector pick up the slack? That's the administration's claim, but it strikes me that somebody's been overdosing on the Hopium(tm). Going into space, particularly going further than low earth orbit, is a long-term, costly, risky, and technically complex project that actually involves building stuff. Back in the days when Visionaries ran the big publicly-held companies, something of that magnitude might have been possible. But these days, most of the decision-making power in a publicly-held company resides with the Wall Street Herd, who are looking only for whatever creates a short-term spike in share prices (most typically the announcement of layoffs). And privately-held companies, while they're more immune to the Herd's influence, just aren't big enough to tackle much beyond low orbit. Elon Musk's SpaceX is doing some cool stuff, but his fortune is what, four or five billion. Nowhere near enough for a moon mission.

So what about the Russians? While they've been by far the most steady space-faring nation, having had the ability to put people in orbit continuously since about 1966, they've said they have no interest in the moon.

Which leaves the Chinese, who've also put a couple people into orbit. But China's historically not been an outward-looking country. There's the tale of the Chinese emperor who built a big fleet and sent it off to explore. When the admiral returned and reported there was nothing out there as magnificent as China, the emperor ordered the fleet sunk. Unless the moon turns out to be inhabited by aliens who'll produce export goods for even less than the Chinese workers do, it's unlikely that China will spend the money to land there.

So, in answer to the question "who will be the next to send people to the moon?" the most likely answer seems to be "nobody." Perhaps the moon race of the 1960s was just a Cold War aberration, something never to be repeated. Could be that a million years from now, when our species is long gone, replaced by either something we constructed as an obedient servant (oops) or perhaps by a More Perfect Cockroach, aliens will land on the moon. There, they'll find the names of four human beings, all that remains to mark our time on this planet.

One of those names, of course, will belong to Tricky Dick Nixon.

Sunday, February 7, 2010

Best Facebook Page Ever?

So this morning I fired up the ol' web browser and went over to Facebook to see if anyone had anything of great cosmic interest to say, and this is what popped up as the "Top Stories" in the "News Feed" view:

Hmm. No posts to display. No news out there at all. Cool... "Use the Publisher above to add your own." Or, perhaps, close the Facebook window and get on with your life... Sounds like a plan to me...