Tuesday, April 15, 2008

Smells of a Summer Night

Because Veena asked about 'redolent mornings' but because I no longer know what mornings look like. I thought I'd do evenings instead.

Raat ki Rani.




Slightly melted tar.

Diesel from generators.

Dead (and decomposing) rat.

Hands, after they're done putting away a couple of rusty and green metal foldable chairs.


I thought basic science taught us that when the air gets hot it gets light and rises. Why do smells sit so heavily in the summer?


km said...

I say let's ravage through other Bergman titles for blogposts :)

//why does "slightly melted tar" remain, er, stuck in my memory even though I haven't smelled tar in like 20 years?

Banno said...

The diesel of generators, now that's a smell I could do without.

the smell of rust, hmm, long time since i smelt that.

Rahul said...

I thought basic science taught us that when the air gets hot it gets light and rises. Why do smells sit so heavily in the summer?

You want a serious answer? :)

My semi-serious answer would be: 1. Things smell more when they're warm. 2. The air is stiller in the summer, so the smells linger.

I used to have the question to my schoolteachers: if hot air rises, why is the atmosphere cooler at higher altitudes? (The answer is not trivial, which I suppose is why nobody explained it to me.)

Itchingtowrite said...

may i answer Rahul's query- chck ypou rbasics on gas laws- pv=nrt- u will get a logic there
plus check this- http://www.usatoday.com/weather/resources/askjack/2004-06-23-cold-upper-atmosphere_x.htm. it explains a lot
everything is a combination of various laws cannot be explained in isolation.

answer to your question- why smell sit heavily in summer-
they don't sit heavily- they diffuse faster in summer when the carrier- air is warmer and threfore moving faster. in winter the air is not moving fast as it is cold & smell molecules r not diffused as far and wide that's why it is easier to smell the smells in summer than winter.

Rahul Siddharthan said...

itching to write: yes, I know the explanation. As I said, it's not trivial. (For example, if it's just that the earth is heated up first and in turn heats the air, why are hill stations cool?) But let's not convert this to a science forum.

Rahul Siddharthan said...

itchingtowrite -- ps. I couldn't let the diffusion argument pass (sorry). The temperature in the summer is not all that different from the winter when measured on an absolute scale: 40 deg C = 313 kelvin, 10 deg C = 283 Kelvin. You can work out the average velocity of an air molecule (let's say nitrogen) from equipartition: the kinetic energy of a molecule is 3/2 kT where T is the temperature and k is Boltzmann's constant. This gives the velocity of a molecule to be 500 metres/sec in winter and 530 m/s in summer (roughly).

If you're talking about a heavier molecule (the sort of organic molecule that you would actually "smell"), the velocity will still be several tens of m/s and the difference in summer vs winter will be very little.

Things smell more in summer because of the difference in biochemical activity at different temperatures (which is very significant), and perhaps the sensitivity of your nose (I'm not sure about that), not because of the air.

All -- sorry if that bored you.

Space Bar said...

km: Someone will kill me if ravage any more - very likely Falstaff. Or Death (who might, actually, just invite me to play chess, which is much worse.)

banno (and everybody): I forgot to say that for some reason summer reeks of cliches. So in case anyone was politely refraining from pointing that out, don't hesitate!

Rahul/Itchingtowrite: Thanks! And I mean that very seriously. It amazing how much basic science I realise I've forgotten or never knew.

And Rahul, I actually clicked to see which one of you it was! :D

Veena said...

SB: C'mon on now. Playing chess with Death is heights of coolness. I will make a movie on you and Death called shatranj ke khiladi which you can then edit and everyone can watch and you know what that leads to, no?. Too cool. So original I am!

Bottomline - I am with km. We want more Bergman title posts.

km said...

Little fairies in pink tutus carry odor molecules on the tips of their wings and spread cholera and dysentery. That's the only explanation.

//Rahul: Bored?? This is fascinating.

Is the air really "stiller" in summer? I would imagine the air in summer has more dust, pollen, "eddies" etc.

//I remember reading a similar question on The Straight Dope and he casually mentioned "adiabatic cooling". Anyone wants to tear through that explanation?

Space Bar said...

Veena: It's not Death I have a problem with; it's the chess. Now if he offered to play hopscotch with me...

km: adiwhat?

Rahul Siddharthan said...

km - links? Adiabatic cooling sounds sort of irrelevant here. (It's what happens when you let a hot object do work without exchanging heat, like using a hot gas to drive a piston by expanding.)

??! said...

summer reeks of cliches
and ditches.