Thread: How does smell travel?

Is it true that a good nose can smell the lighting of a cigar across a perfectly calm gymnasium in an instant? How about a coliseum?

Originally Posted by Wolf50

Is it true that a good nose can smell the lighting of a cigar across a perfectly calm gymnasium in an instant? How about a coliseum?

Absolutely not. Absent a driving force, air moves extremely slowly. Because the cigar lighter heats the air, the hot air will rise until it reaches ambient temperature. But, in terms of moving about the building, it will not. If the building is unoccupied with the HVAC turned off, then the odor of the cigar will remain localized in the same spot for days if not weeks.

i would think that EVENTUALLY the smell would make it's way across any room, given that the source gives off enough odor so that it does not dissapate as it makes it's way across the room.
I get what MisterMe is saying and it does make perfect sense.
But if you fill a glass with water. Let it sit so it becomes room temperature. This way the temp is uniform throughout the cup and convection currents are removed. Then put a drop of food coloring in it, the food coloring will eventually distribute evenly throught the glass, even though the water is perfectly still.

why is this?

i understand the food coloring has slightly different peoperties than the water, but i dont think thats too much of a problem, seeing as how the dye does not float to the top or sink to the bottom, it distributes uniformly.

Originally Posted by Joe McCarron

...
But if you fill a glass with water. Let it sit so it becomes room temperature. This way the temp is uniform throughout the cup and convection currents are removed. Then put a drop of food coloring in it, the food coloring will eventually distribute evenly throught the glass, even though the water is perfectly still.

...

It happens that I have seen a similar demonstration:

There was a large tank of water at room temperature. Into the tank was poured hot water with blue food coloring. One might think that the hot blue water would have equilibrated with the uncolored water, mixed, and disappeared into a tank of blue-tinged water. This did not happen. The hot blue water stratified into a sharp-edged thin blue layer with virtually no mixing with the uncolored water. The blue layer hovered a few centimeters above the bottom of the tank.

If you have access to a casserole dish, glass saucepan, or fish tank [without fish], then you may perform the experiment for yourself. You will find that the water mixes only when you mechanically agitate it.

Originally Posted by Joe McCarron

...
But if you fill a glass with water. Let it sit so it becomes room temperature. This way the temp is uniform throughout the cup and convection currents are removed. Then put a drop of food coloring in it, the food coloring will eventually distribute evenly throught the glass, even though the water is perfectly still.

...

It happens that I have seen a similar demonstration:

There was a large tank of water at room temperature. Into the tank was poured hot water with blue food coloring. One might think that the hot blue water would have equilibrated with the uncolored water, mixed, and disappeared into a tank of blue-tinged water. This did not happen. The hot blue water stratified into a sharp-edged thin blue layer with virtually no mixing with the uncolored water. The blue layer hovered a few centimeters above the bottom of the tank.

If you have access to a casserole dish, glass saucepan, or fish tank [without fish], then you may perform the experiment for yourself. You will find that the water mixes only when you mechanically agitate it.

Originally Posted by Joe McCarron

...
But if you fill a glass with water. Let it sit so it becomes room temperature. This way the temp is uniform throughout the cup and convection currents are removed. Then put a drop of food coloring in it, the food coloring will eventually distribute evenly throught the glass, even though the water is perfectly still.

...

It happens that I have seen a similar demonstration:

There was a large tank of water at room temperature. Into the tank was poured hot water with blue food coloring. One might think that the hot blue water would have equilibrated with the uncolored water, mixed, and disappeared into a tank of blue-tinged water. This did not happen. The hot blue water stratified into a sharp-edged thin blue layer with virtually no mixing with the uncolored water. The blue layer hovered a few centimeters above the bottom of the tank.

If you have access to a casserole dish, glass saucepan, or fish tank [without fish], then you may perform the experiment for yourself. You will find that the water mixes only when you mechanically agitate it.

that sounds really neat, i gotta try that.

So does science know how smells move or not?

Originally Posted by Wolf50

So does science know how smells move or not?

Of course they do. Nothing in my previous posts implies otherwise. Odors are caused by gases in the atmosphere. These gases move with the air. Your OP was a question about how fast do odors move. The answer is that odors move very slowly left to their own devices. This is because air moves very slowly absent some driving mechanism.

Originally Posted by Wolf50

So does science know how smells move or not?

Does "Science" know? What is this "Science" you speak of? Is it an institution? A person? You use the word as a noun.

Do you mean, "Can the motion of smell and olfactory senses be scientifically explained?" Or- "Does the scientific method shed any light on the sense of smell?"

The answer to those questions would be something like, "Uh. Yes."
Let me google that for you

Olfaction - Wikipedia, the free encyclopedia

Well, let's see... when we Smell something, it's because we are "tasting" particulates, molecules and particles that are suspended in air. As air in a given area moves around, diffuses, is blown, agitated or by many other means of entropy-moved, these particulates that are related to the specific scent you may have in question are carried along with all the other dust and particulates and molecules in the air. When they reach your nose, your nose "tastes" them and a signal moves to your brain saying, "Found a stink, here."
Fluid dynamics - Wikipedia, the free encyclopedia

"Science" did done a good job!