We’re only aware of events if they don’t happen too quickly. Rustling leaves, swooping birds, meteors — stuff we can see. But an ultrafast world surrounds us.
Just below that threshold lies our everyday lives. We swat a fly, it leaps out of the way within a tenth of a second, which happens to be the same interval as an eye blink. This outwits some fast-reflexed animals like cats, which can’t reliably catch flies. But monkeys can almost effortlessly pick flies up. Chickens routinely peck flies off surfaces.
In the animal kingdom, the fastest phenomena involve the startle reflexes, which have evolved as lightning-quick defensive responses. They work by using neural mechanisms that completely bypass cerebral processing and voluntary control. Since these neural circuits are shorter, the time periods of the startle reactions are much quicker than those of voluntary actions.
Moles, which most of us hardly regard as sprightly, react as soon as their nasal appendages contact a potential food source underground, and strike out in a seventh of a second, about the time it takes to say the second “pa” in the word papa.
All around us, non-biological processes occur even faster. Many chemical reactions happen in an eyeblink, although other reactions like iron oxidation (rusting) can take years to unfold. The very fastest is the simple creation of water from the bonding of oxygen and hydrogen. The protons assume their new positions on a femtosecond timescale — a few trillionths of a second.
The H2O molecule is what our bodies are mostly made of, but it’s strange that it’s a liquid. It’s such a small, featherweight molecule, composed mostly of the tiniest atom in the cosmos, it ought to be a gas at room temperature. In earthly conditions, all other molecules of water’s size, like methane (CH4) and carbon dioxide (CO2) are gases. Methane boils from liquid to gas at -258 degrees Fahrenheit, compared with water’s unbelievably high +212°F. But if water behaved like methane, Earth would be lifeless.
Recent studies show that such hydrogen bonding to create water happens barely longer than a trillionth of a second. But in that femtosecond frame, a momentary structure exists that makes the molecule act as if it were much larger than it really is. Water acts like a fluid and not a gas at room temperature even though those larger structures come and go a hundred times in each billionth of a second.
Not all chemical or physical reactions are that fast, of course. The speed depends on such things as the concentration of the substance, whether it’s a gas, liquid, or solid, and especially on its temperature. Turn up the heat and things speed up. That’s why we use a match to reach the critical ignition point where oxidizing (“burn”) reactions can begin. In most common combustibles, the object’s hydrogen combines with oxygen in the air, leaving behind carbon as residue or ash. Such reactions are exothermic, meaning they create heat. Thus, once started, they supply enough heat to self-sustain.
It makes sense that the hotter something is, the faster reactions will proceed, since bonds are being broken, excitations occurring, and more contact between atoms is happening. To use real numbers, room temperature atoms jiggle around at between 600 to 1000 miles an hour. Those in your freezer go 50 m.p.h. slower.
The speed and excitation required to begin the self-sustaining reaction called “burning” depends on the substance. A match’s fire boasts a temperature between 1112°F at its low point to 1472° at its tip, when its molecules move so fast they can set in motion those in most other substances, making them reach a speed that lets them start the burn reaction on their own.
Wood will openly ignite when exposed to between 374° and 500°. Paper “catches” more easily. Its ignition temperature (which varies depending on the paper) famously lies around 451°F, the title of the 1953 Ray Bradbury novel and later movie. Coal ignites at 842°. Kerosene at 444°. Gasoline will go up at 495°, alcohol at 689°. The point is, it’s all motion. When you run a fever, you might complain that you have 102°. But you could just as well tell the doctor, “My body’s molecules are moving three miles per hour faster than normal.”
Then (at least in the old days when physicians dispensed medicine) he’d hand you some aspirin, saying, “Here. This will slow them down.”
In the night sky, stillness rules with just a few exceptions. The moon’s motion can indeed be observed as it sets into a flat oceanic horizon, but it’s barely perceivable, happening with the same movement as the minute hand on a wall clock. Fast action – our current theme – is restricted to meteors, like the Perseids that will peak on August 12.
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