Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: THURSDAY, May 5, 1994 TAG: 9405050135
SECTION: EXTRA PAGE: 3 EDITION: METRO
SOURCE: Joel Achenbach
DATELINE: LENGTH: Long
A: Fog has a relative humidity of 100 percent. Precisely. On the nose. Bingo. Exactamundo. Indubitably. So why doesn't fog feel gross, like ``humidity''? Why, in fact, does fog sometimes feel good, kind of refreshing and sweet, while ``humidity'' feels like you may have to gouge out your eyeballs merely as a distraction?
You know of course that fog and humidity are water-related climatic phenomena. What's the diff?
For one thing, fog is liquid water suspended in the air, while relative humidity refers to how much water vapor - gas -is in the air relative to how much the air could hold. When we say it's humid we mean that there's a lot of water vapor in the air. It gets tricky because in fact the very unpleasant, muggy, suffocating 90-degree days of summer often have a relative humidity of only 50 percent or so, which sounds kind of low. The reason that number is low is that hot air can handle a vast amount of water vapor. Cool air can't.
That's why you get fog, because the cool air can't handle the water vapor and it condenses into a liquid. Foggy air at 45 degrees has a lot less water in it than sticky, gummy, goopy air at 90 degrees, even though the ``relative humidity'' is 100 percent in the cool fog and maybe only 50 percent in the hot humid air.
As for why fog doesn't make you uncomfortable, that's so simple we'd probably be too embarrassed to even write the explanation were we not desperate for column material. If we're dressed well, a cool fog doesn't bother us. But if we're hot and sweaty, humid air is a nightmare, because the sweat can't easily evaporate into the already saturated air. We just stand there soaking, a globule of fluidity, sopping wet saps, losers.
So remember, everything depends on the temperature of the air. We are tempted to say that it's not the humidity - it's the heat.
Q: Why do we have daylight-saving time in the summer even though that's when there's no shortage of daylight?
A: Admit it: You always assume daylight-saving time (or Daylight Savings Time as we'd call it if our stylebook wasn't so darn fussy) is an elaborate way of warding off darkness. That daylight-saving time somehow converts nighttime into daytime. But mostly you just don't think about it: You are a sheep, following orders, biannually turning your clocks forward or backward and struggling to calculate whether this means you can sleep late.
Well dig this: We have daylight-saving time in the summer because in the summer we have too much daylight.
The whole point is to shift light from morning to evening, because it gets light so early in the summer months. We don't need it to be light at 5 in the morning unless we are farmers. Farmers don't like DST much.
What would happen if we didn't set our clocks forward on the first Sunday in April? Hell on Earth, basically: In Washington, D.C., just to take a city randomly out of the atlas, the sun would rise at 4:43 a.m. on the 21st of June, according to astronomer Leroy Doggett of the U.S. Naval Observatory. That means that ``civil twilight,'' when it's light enough to do outdoor activities, would begin at about 4:11 a.m., when the sun is 6 degrees below the horizon. The first light in the East would appear about half an hour before that.
Yes: Three-something in the morning. You can see the ghastly possibilities: You wake up in the morning without checking the clock, make coffee, shower, drive to work and suddenly discover it is only 4:15. Thus to prevent that the government makes sure every year to alter time itself.
The Mailbag:
Brandon A., age 6, of Springfield, Va., asks, ``Why does Washington have a monument when Lincoln and Jefferson have memorials?''
Dear Brandon: Yeah, and why does Kennedy only have a ``Center''?
We called Earle Kittleman, a spokesman for the National Park Service, and he said the monument/memorial distinction is meaningless. ``Their names do not connote different categories of importance,'' he said.
But that still doesn't answer your question as to why it's not the Washington Memorial or the Lincoln Monument or whatever. Kittleman's guess is that when they built the Washington Monument, officials simply thought ``monument'' was the right word, and later they thought ``memorial'' sounded right. That explanation may seem lame but it does fit into the larger truth that most things in life are random, inexplicable and fundamentally unfair.
We'd also venture that the Washington Monument is clearly a monument - it's just a big ugly spike, a dull-witted slab that seems to be making the obvious point that Washington was Numero Uno. Washington is also memorialized in the name of the capital city. Meanwhile, the Lincoln and Jefferson memorials are not really that monumental; they're big and grand, sure, but they have a quieter grace that invites reflection and memory.
For something really unmonumental you have to go to Roosevelt Island, the memorial to Teddy. It's literally an island in the Potomac River, mostly just woods and trails. You get there by taking the George Washington Memorial Parkway. (They really don't want you to forget Washington around here, do they?)
Washington Post Writers Group
by CNB