Saturday, January 26, 2019
Think it's foggy?
Superfog this morning. The curtain is about 100 feet away.
A good demonstration of how senses are always measured from a baseline.
Normally Spokane's air is so dry that smells don't stick around. Our olfactory baseline is adjusted to those conditions.
Fog holds every smell for a long time. Last night I got scared by an intense smoke smell in the house. Turned out to be from a neighbor's woodstove, not a fire in here. Normally woodsmoke dissipates and doesn't penetrate. Normally an intense smell means it's RIGHT HERE.
Similar phenomenon:
Normally the propane smell would dissipate quickly. Today it hung around and intensified, which quite properly triggered an alarm in the person who called.
= = = = =
Separate and probably stupid thought about fog. We "naturally" know that fog doesn't get into a building. This is physically true for modern buildings with forced-air heating and air conditioning. Both systems decrease relative humidity. But it's NOT automatically true for older heating systems, or in moderate weather with the windows open. Fireplaces and steam radiators ADD humidity. Despite this, we know that we can "go inside away from the fog."
Is it just a question of distance? When we're in a 10-foot room, all visible objects are well within the 100-foot curtain. The curtain effect is exponential, so the first 10 feet has zero observable attenuation.
An open window with a cold metal screen acts as a condenser, like an inefficient air conditioner; but this wouldn't work with a nylon screen or an unscreened window.
Or is our "intuition" correct in assuming that fog can't come inside?
A good demonstration of how senses are always measured from a baseline.
Normally Spokane's air is so dry that smells don't stick around. Our olfactory baseline is adjusted to those conditions.
Fog holds every smell for a long time. Last night I got scared by an intense smoke smell in the house. Turned out to be from a neighbor's woodstove, not a fire in here. Normally woodsmoke dissipates and doesn't penetrate. Normally an intense smell means it's RIGHT HERE.
Similar phenomenon:
Normally the propane smell would dissipate quickly. Today it hung around and intensified, which quite properly triggered an alarm in the person who called.
= = = = =
Separate and probably stupid thought about fog. We "naturally" know that fog doesn't get into a building. This is physically true for modern buildings with forced-air heating and air conditioning. Both systems decrease relative humidity. But it's NOT automatically true for older heating systems, or in moderate weather with the windows open. Fireplaces and steam radiators ADD humidity. Despite this, we know that we can "go inside away from the fog."
Is it just a question of distance? When we're in a 10-foot room, all visible objects are well within the 100-foot curtain. The curtain effect is exponential, so the first 10 feet has zero observable attenuation.
An open window with a cold metal screen acts as a condenser, like an inefficient air conditioner; but this wouldn't work with a nylon screen or an unscreened window.
Or is our "intuition" correct in assuming that fog can't come inside?
Labels: Asked and badly answered
¶ 8:57 AM
