Says Dave in New York City: “I love that this note contains a fairly detailed explanation of Lord Kelvin’s formulation of the second law of thermodynamics….and a helpful diagram!”
related: When you get down to it
When Ph.d.s get frustrated
June 3rd, 2007 · 115 comments
FILED UNDER: "helpful" advice · college life · It's science! · most popular notes of 2007 · temperature · TL;DR · visual aids
115 responses so far ↓
#1
Rigby
That’s truely the best. I love the diagram.
Jun 3, 2007 at 5:34 pm rating: 90
#2
TTFK
So he’s a PhD, and he makes a drawing of hot air FALLING?
Jun 3, 2007 at 6:06 pm rating: 90
#3
Catsoup
Pfft. I’d be more impressed if he’d used blue ink to indicate the cold air.
Jun 3, 2007 at 6:51 pm rating: 90
#4
Artorios
Hahaha
Jun 3, 2007 at 7:26 pm rating: 90
#5
Anhoni
All he had to say was “Don’t run the A/C with the window open, it wastes electricity.”
Jun 3, 2007 at 8:02 pm rating: 90
#6
Mark Davis
this note isn’t passive aggressive. it has a specific request and logical rational reasons.
Jun 3, 2007 at 8:47 pm rating: 90
#7
Suzi
Okay, I’ve been reading this web site obsessively since I stumbled upon it a week or so ago, and this is my favorite one so far. Brilliant.
Jun 3, 2007 at 9:26 pm rating: 90
#8
Jordan
Mark Davis is right, in the end.
Jun 3, 2007 at 10:16 pm rating: 90
#9
andyfox1979
truly a scientist.
Jun 3, 2007 at 10:31 pm rating: 90
#10
Adam
Absolutely the best PA note thus far. Let’s start a ‘note of the week’ or something here
Jun 4, 2007 at 12:14 am rating: 90
#11
babychaos
I reckon Mark Davis wrote the note.
Cheers
BC
Jun 4, 2007 at 11:52 am rating: 90
#12
Michael
The room won’t necessarily get hotter. If the cold air blown into the room minus the hot air generated by inefficiencies in the unit is greater than zero then you have a net decline in heat. It doesn’t matter that the A/C blows hot air outside because that shouldn’t effect the temperature inside. It could make a difference if there’s a constant draft going into the room that draws all the heat from the unit in with it but that probably doesn’t happen too often. It still wastes a lot of electricity though. Blowing a fan over a bucket of cold tap water would be a lot more efficient.
Jun 4, 2007 at 12:03 pm rating: 90
#13
phampants
i’m glad ph.d. students have so much time
Jun 4, 2007 at 12:48 pm rating: 90
#14
Veritas
Am I mistaken or did he spell it vary instead of very?
Jun 4, 2007 at 12:52 pm rating: 90
#15
jane
Best one so far….
Jun 4, 2007 at 6:21 pm rating: 90
#16
V
hmmm…hard to determine whether this is P-A or just plain TMI. Sometimes, it’s best to just say what needs sayin’ (like Anhoni stated), without the lesson.
Jun 4, 2007 at 6:58 pm rating: 90
#17
kat
i love this one. the best so far!
Jun 5, 2007 at 2:33 am rating: 90
#18
Sharkie
This is the best post on this site!
Jun 8, 2007 at 12:28 pm rating: 90
#19
Velly
The hot air probably _would_ travel in direction of the open window because the temperature inside the room would be cooler than the temperature outside. Heat always moves to achieve equilibrium — to eliminate “cold”.
Jun 26, 2007 at 3:39 pm rating: 90
#20
Matthew
Neat, cool lesson.
Jun 26, 2007 at 4:12 pm rating: 90
#21
Chak
You dont need a PhD to explain that, a B.S. (bullsh*t) degree would do just fine :P.
He also completely ignored the fundamental fact that hot air rises. I’d question where he got his PhD from.
Jun 26, 2007 at 7:03 pm rating: 90
#22
msquared
Ph.D = piled higher and deeper
Jun 26, 2007 at 7:27 pm rating: 90
#23
ned
copied almost word for word from the howstuffworks.com air conditioning article.
Jun 27, 2007 at 2:07 am rating: 90
#24
Marc
I do not see this as a passive-aggressive note. He may or may not be 100% correct, but he follows a logical reasoning and makes fair efforts to convince the reader to reach the same conclusion, he’s just being assertive which is completely OK.
Jun 27, 2007 at 4:58 am rating: 90
#25
Webmaster X
“Michael // Jun 4, 2007 at 12:03 pm
The room won’t necessarily get hotter. If the cold air blown into the room minus the hot air generated by inefficiencies in the unit is greater than zero then you have a net decline in heat. It doesn’t matter that the A/C blows hot air outside because that shouldn’t effect the temperature inside. It could make a difference if there’s a constant draft going into the room that draws all the heat from the unit in with it but that probably doesn’t happen too often. It still wastes a lot of electricity though. Blowing a fan over a bucket of cold tap water would be a lot more efficient.”
Boy you sure don’t have a fucking clue what you are talkingabout.
Jun 27, 2007 at 5:17 am rating: 90
#26
Rickyp
Why is this by a Ph.D.? Anyone who has taken an undergrad course in thermodynamics would understand this principle. I would be inclined to say that no engineer with a Ph.D. would be doing justice to his argument without mentioning entropy. The net increase in entropy makes the process irreversible and thus a greater quantity of energy than that which is removed from the air entering the room is released into the atmosphere, meaning that if that exhausted air were to enter the room, the total energy in the room would increase. As far as the hot air falling thing is concerned, the difference in pressure between inside and outside is what controls the movement of air more than convection in an open system like this. If the inside is cooler, then there will be a pressure drop outward through the window and the air will tend to flow outward, expelling cold air and replacing it with whatever is in the hallway or reaching a dynamic equilibrium with the outside. Alternately, if it tends to be warmer inside then the air from outside will be sucked inside by the pressure difference, pulling in the hot exhaust and lowering the pressure further and pulling in more hot exhaust until the room is the same temperature as the hot exhaust. Buildings are normally not warmer than the atmosphere (unless it’s a greenhouse or a sauna). Thus, even with the window open one needs not worry too much about the exhaust, that is unless the prevailing winds blow air into the building or perhaps if the wind creates a vacuum on another face of the building (wind blowing perpendicular to a wall with a number of open windows). In general, with such a large system, convection has nothing to do with how the heat flows. But again, I doubt this was a Ph.D., since there is no mention of entropy, and anyone who knew a lot about how heat pumps work (at least anyone who has completed at least a year and a half of chemical engineering coursework) would not be doing the argument justice without mentioning entropy.
Jun 27, 2007 at 5:40 am rating: 90
#27
SirOJ
@Rickyp… you’re an ass… nobody cares you know.
Ned was spot on: copied form howstuffworks.com
Jun 27, 2007 at 5:54 am rating: 90
#28
Levi
Rickyp is not an ass; he’s clarifying for a lot of the people here who seem to have stopped thinking about science in elementary school. “What an idiot, hot air rises man!!!!” . . .
Another ironic thing is that people here seem to be anti-knowledge, as if they are the hall monitors for the school of dunces. First the note was attacked and now Rickyp. Perhaps the world would be a better place if more people sought understanding of and explanations for things instead of taking things straight from the horse’s mouth.
Jun 27, 2007 at 8:42 am rating: 90
#29
Fuck You
Dear asses:
The request is perfectly reasonable. PhD students’ time is cheap because society does not value original thought and the wages reflect this.
Hot air gets sucked into a vacuum, whether it is a literal vacuum (pressure out of equilibrium) or a figurative vacuum (order tends to disorder, as we all observe daily).
Whoever is running A/C with a window open would probably fit right in with the comments. How fucking stupid do you have to be to do this? It’s like trying to carry water in a sieve.
Please do your part to control the population explosion, and kill yourself. Thanks!
Jun 27, 2007 at 8:54 am rating: 91
#30
me
Anhoni: all you had to say was nothing.
Jun 27, 2007 at 9:32 am rating: 90
#31
Mantra
Sound like any engineer. Most PhD’s aren’t that practical – even the one’s in engineering. As an engineer, believe me, dealing with numerically and scientifically illiterate (90% of US population) is very trying at times.
Just yesterday they had Fox news on in the customer cafeteria I was visiting and the dorkbot on the show was looking at a straw poll of Hillary-vs.-McCain which stated that 46% Hillary – 43% McCain with 8% margin of error, and yet the idiot was claiming conclusions from the numbers. Don’t worry I won’t derive confidence intervals and random chance, but the numbers made it self-evident that nothing at all could be concluded. Anyone with a high school diploma should have got that. News is about things that rarely happen – most of the time there is no news. It’s a bad business model which is why we have infotainment instead.
Jun 27, 2007 at 10:03 am rating: 90
#32
anonymoustroll
Someone should remind the good doctor that PhDs are very similar to air conditioners running next to a open windows.
Jun 27, 2007 at 11:05 am rating: 90
#33
Bulbboy
Is this why politicians who blow hot air all the time are ineffective when speaking outside?
Jun 27, 2007 at 5:56 pm rating: 90
#34
xian
Most of these notes, while funny, are not passive-aggressive, unless we are redefining the term (see also ‘ironic’), but to mean… what?
Jun 27, 2007 at 11:50 pm rating: 90
#35
LK
i think this note is passive aggressive. the guy went into a completely unnecessary explanation with a completely unnecessary diagram, hinting that he thinks (sarcastically or not) that his roommate is extremely stupid. i think this makes it PA. if he had just said “hey don’t run the AC with the window open” then it certainly wouldn’t have been PA.
Jun 29, 2007 at 6:18 pm rating: 90
#36
conformist_panda
Writing: “Please do not run the air conditioner with the window open. You are killing the planet! (plus God kills a kitten.)” would be better, don’t ya think?
Jun 29, 2007 at 7:32 pm rating: 90
#37
RaggDolly121
He explains things too often.
Jul 2, 2007 at 2:11 pm rating: 90
#38
Jeff
So he’s a PhD, and he makes a drawing of hot air FALLING?
Actually, the hot air is not falling, it is being sucked into the window by the displacement of warm air inside the room… And I only hold a bachelor’s degree… In THEATRE! hehehehehe
Jul 2, 2007 at 6:44 pm rating: 90
#39
Jeff
Whoever is running A/C with a window open would probably fit right in with the comments. How fucking stupid do you have to be to do this? It’s like trying to carry water in a sieve.
Actually, I carry “water” in a “sieve” all the time. Its called a bank account.
Jul 2, 2007 at 6:46 pm rating: 90
#40
johnO
I dunno, I think you give the guy too much credit by calling him a PhD. There’s some questionable stuff in his “science”/reasoning.
But who has heard of a window with an A/C unit that can open??? This one gives me a BS-alert impulse.
Jul 2, 2007 at 11:18 pm rating: 90
#41
ThatGuy
I am smarter due to this note and I appreciate the sharing of such knowledge!
Jul 11, 2007 at 7:41 am rating: 90
#42
Midlife Crisis
If you wish to leave the window open, then the air conditioner should be reversed so it blows the cold air outside and the hot air inside. The cold air falls, mixing with fresh air, and then is drawn back into the room by the mild temperature gradient and stays close to the floor. Inside, the hot exhaust air rises quickly to the ceiling, forcing the cooler air down to where people are working. However, one must be careful not to over-cool the room because, depending on the relative humidity, ice may start to form on computer monitors and other electronic equipment causing an electrical hazard and subjecting workers to potential hypothermia.
Jul 16, 2007 at 6:52 pm rating: 90
#43
N8tiv tung
Bulbboy #39 This is part of the reason. Actually, most politicians are ineffective regardless of location, because they both suck AND blow. Administrators, too (although the two are not much different in basic composition).
Jul 17, 2007 at 8:36 pm rating: 90
#44
Jill
Methinks I should have written a diagram like this for my husband, who often is guilty of leaving windows open while the AC is on. Of course, I have no such knowledge of which way different temperatures of air flow…my reasoning is that it’s too damned expensive to air-condition all of VA (which is what he’s doing when he doesn’t bother to contain that pricey cold air in our home).
Now, where’s a note from someone who is tired of roommate/spouse running the AC when it is less than 50 degrees outside? THAT’S one I can’t wrap my brain around, either.
Jul 18, 2007 at 10:25 pm rating: 90
#45
Zelda
God I wish I could sneak a camera into my lab…I can’t think of a place more full of passive aggressive asocial weirdos. They put notes on EVERY piece of lab equipment. It’s like no one can communicate verbally… the signs in the bathroom are priceless. I may have to risk my job to document the insanity because it is just too good.
Jul 24, 2007 at 2:47 pm rating: 90
#46
jane
i’m going to print this out. my roommates always leave the windows open with the AC on.
Jul 30, 2007 at 9:19 am rating: 90
#47
Mishee
I’m going to comment on this just so it hopefully goes up to the “Stirring Up Trouble” – I want to see what our current gang of troublemakers can say about this post…
The diagram reminds me of my dad!
Oh, and that cold air is fucking delicious!
Nov 8, 2007 at 6:50 pm rating: 90
#48
Jodi Blaze
Doctor Doctor, Give me the news
I gotta bad case of drawing things
Nov 28, 2007 at 5:13 pm rating: 90
#49
Chrissie
The rules of air conditioning should be started in the by-law process. I have a similar problem, too.
Dec 7, 2007 at 12:53 pm rating: 90
#50
Nichole
I Don’t Know What I Can do to tell my Parent’s that I need my own Computer and I don’t Have Not enght of Money to by it and I Don’t Know What I Elease to Tell them. From your friend Mida Nichole
Dec 24, 2007 at 11:35 am rating: 90
#51
dsfkjdf;kjf;lkj
did no one notice the hair stuck in the piece of tape on the note? ewwwww …
Jan 6, 2008 at 12:26 pm rating: 90
#52
sir jorge
i’d shove that paper in that phd’s mouth.
Apr 23, 2008 at 6:52 pm rating: 90
#53
Cricket
Dear Stupids,
if you’re gonna run the A/C, keep the window closed.
-Me
Jun 12, 2008 at 2:31 pm rating: 90
#54
Cricket
picture pages, picture pages!
time to get your picture pages!
time to get your crayons and your pencils!
picture pages picture pages!
open up your picture pages!
time to watch this psycho
do a picture page with you!
Jun 12, 2008 at 2:36 pm rating: 90
#55
db
Also, someone want to translate this into Italian and post it on the Italian Regional trains? Each window has a huge sign saying the cabin is air-conditioned. No matter how nice and cool and refreshing it is in the cabin, some IDIOT always comes on and opens a window. I had my first real, sparks-flying argument in Italian over this. It was great! lol
Jul 10, 2008 at 5:42 am rating: 90
#56
Aww... Crapsticks
Firstly, the guy never called HIMSELF a Phd so all the “he ain’t so friggen smart” angst is a little unwarranted.
Secondly, this IS a passive aggressive note in it’s highest form- the key is in the subtle aggro.
Thirdly, I must be right in my assertions because I am making my points sequentially and starting them with linear numerical value. So you know I’m a clever fuck.
Jul 17, 2008 at 10:38 am rating: 90
#57
jimoser
Where I come from, if you open the window the A/C unit falls out crushing the unsuspecting students below. I’m not sure if that makes the room any warmer. Perhaps a diagram could could answer the perplexing question.
Aug 11, 2008 at 2:41 pm rating: 90
#58
SMF
Actually if that is a powerful enough AC unit it will Positivly pressurize the room and no air will come in that window.. Just like a Hospital Isolation room
Aug 26, 2008 at 11:44 am rating: 90
#59
chipmunk
A friend sent me this link… I guess people (my friend included) have way too much time in their hands to the point that actually can waste it to read these threads and comment on it… despite my remark, I could not resist leaving a comment… LOL
Get an hobby, or a life… whichever you prefer! ;D
Sep 9, 2008 at 11:57 pm rating: 90
#60 the nerd’s guide to passive-aggressive behavior
[...] related: when ph.ds get frustrated [...]
Dec 15, 2008 at 12:29 pm rating: 90
#61
Claire de Lune
I don’t have a PhD, but I DO know that you DONT run the a/c with the window open. You don’t need to draw me a picture.
Dec 25, 2008 at 1:35 pm rating: 90
#62
Jamey
But warm air rises. So the drawing is inaccurate: If the a/c unit is top-mounted, the “very hot air” exhausted would not magically drop down and reenter the room. Thus, the net effect really has little to do with the air exchanged by the a/c; it’s more a result of the temperature differential between the room and outside.
Jan 12, 2009 at 4:29 pm rating: 90
#63 sausage shaped, but lumpy
[...] when ph.d.s get angry extra credit: mcsweeney’s open [...]
Jan 21, 2009 at 1:50 am rating: 90
#64
Gillian
I read through almost all the comments, getting more and more perplexed til I got to #67 and #67.1, which said *exactly* what I was going to say — that the “ph.d” is just in the cute little title/caption *about* the note, not IN the note, so who the hell knows if the guy finished kindergarten?
And I vote for Good Intentions. I think the guy (or female — why does it have to be a guy? this is pretty much the exact note I would leave, and I’m not a guy) is probably mad as hell because every time s/he comes home, the a.c. is going full blast and the window is wide open and the place is hot as hell inside.
This nicely diagrammed note is probably the fifth version at least. The first version most likely said, “HEY YOU BRAINLESS ASSHATS WTF DID YOU DO WITH YOUR BRAINS?!?! MAYBE YOU FRIED THEM IN THIS MIND-INCINERATING HEAT?? WHEN THE A/C IS ON, KEEP THE WINDOW CLOSED!! HOLY MOTHER OF DUH!!!!!!!!” And then s/he thought that might not be so effective, and s/he gradually toned the note down until s/he got to this version, which is actualy polite as hell, considering the alternatives, which would be a shotgun or an eviction notice.
.02 :> *shrug*
Feb 9, 2009 at 8:29 pm rating: 90
#65
Janelle Holden
This is a classic case of logic getting in the way of impulsiveness. Awesome site!
Mar 5, 2009 at 6:56 pm rating: 90
#66
Susie_Paloosie
People! You are all missing the obvious. Read #66!
#66 jimoser
Where I come from, if you open the window the A/C unit falls out crushing the unsuspecting students below. I’m not sure if that makes the room any warmer.
Mar 21, 2009 at 6:06 pm rating: 90
#67
mike
are you assuming this person’s a doctor because they understand the basic concept behind how a window unit works?
i understood this in middle school when my dad explained it to me, and HE barely made it out of high school.
it’s really not that hard.
(is posting a passive aggressive note about a passive aggressive note postmodern?)
Apr 26, 2009 at 4:26 pm rating: 90
#68
COURTNEY
Amazing. I love the diagram.
Jun 15, 2009 at 2:21 pm rating: 90
#69
vapor cigarette
I thought it was a great note, and not all that passive aggressive, unless you consider the underlined portions. I think it was very charitable on his/her part to think his/her room mates could even read.
Aug 9, 2009 at 3:06 pm rating: 90
#70
niamh
why do most of the comments assume it’s a “he”?
Aug 10, 2009 at 6:25 pm rating: 90
#71
BoozeInMyBlood
im 87.6% positive that Ronald E. Dahlgren wrote that lil gem. He fancies himself quite the artist.
Sep 19, 2009 at 4:59 pm rating: 90
#72 I’m sure you guys can deal | PassiveAggressiveNotes.com
[...] When Ph.d.s get frustrated [...]
Mar 22, 2010 at 8:49 pm rating: 90
#73 Flowchart: "Hey, look! A coffee pot!" | PassiveAggressiveNotes.com
[...] When Ph.Ds get Frustrated [...]
May 13, 2011 at 9:04 am rating: 90
#74 Hmm, maybe a diagram would help? (Or a spoonful of sugar?) | PassiveAggressiveNotes.com
[...] related: The Ph.D’s approach to air conditioning units [...]
Jun 14, 2011 at 9:57 pm rating: 90
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