Shocking Truths 



If you break the sound barrier, 

 you can make quite a stir. 



By Neil deGrasse Tyson 



No matter what the threshold 

 of your sensibilities, modern 

 life can be shocking. A pas- 

 senger cursing loudly in a crowded 

 subway car may shock your sense of 

 propriety. War profiteering may shock 

 your sense of ethics.Torture may shock 

 your sense of humanity. A scorched 

 forest, a flooded city, a corpse lying un- 

 attended on a street can all be shock- 

 ing sights. 



But none of those scenes is likely to 

 disrupt your personal set of molecules. 

 A wholesale disturbance requires not 

 figurative shocks but literal ones — and 



the cosmos has plenty of them. Huge 

 flares rear up out of the Sun and launch 

 billions of tons of plasma into the solar 

 system at a million miles an hour; gi- 

 gantic rings of million-degree gas race 

 outward from exploding stars; colossal 

 gas clouds, millions of times larger still, 

 plunge into one another as galaxies col- 

 lide, creating bursts of freshly formed 

 stars. Find yourself near any of those 

 phenomena, and you'll have more than 

 your emotions to worry about. 



Twentieth-century technology be- 

 queathed its own versions of extreme 

 shock waves. Some were unleashed by 



the detonation of the atomic bombs 

 "Little Boy" and "Fat Man" over Hi- 

 roshima and Nagasaki in August 1945. 

 Others were loosed by the hydrogen 

 bombs "Mike" and "Bravo" — hundreds 

 of times more powerful than their 

 atomic predecessors — on the Pacific 

 atolls of Eniwetok in 1952 and Bikini 

 in 1954. One hesitates to contemplate 

 the shock waves that might be wrought 

 by twenty-first-century technology. 



Shock waves begin from a simple 

 fact of nature: molecules in a gas 

 are always on the move. Not only do 

 they stretch and shrink and twist and 

 turn and vibrate, they also move, body 

 and soul, from one place to another. 

 In a split second, a meandering mole- 

 cule bounces off neighboring mole- 

 cules, transferring its energy from one 

 to the next, and so on across the gas. 



Intruders, too, can shake up a batch 

 of molecules that are otherwise ]ig- 

 gling away in blissful isolation. When 



September 2006 naturai hisiory 



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