Q: How to stay cool.  I did a test, and found that reversing a ceiling fan (air blowing up) cools a room better.  Craig, Downey, California

Ceiling fan. Photo courtesy of Lamp Depot.

A:  Testing makes sense; indeed, it is the only way to get results you want. 

People often wonder which direction the fan should blow in which season:  summer and winter. 

First, a word on terminology:  Some fans come with a forward and a reverse setting. On "forward", the fan blows the air down. Standing under the fan, you feel a breeze. On "reverse", the fan blows the air up. Now, when you stand under the fan, you feel no direct breeze. 

Warm air collects near the ceiling.  So, during the winter, turn the fan to "reverse" to circulate the warm air without blowing air down and cooling you in the process. A ceiling fan, running in reverse, gently mixes the air, and helps move the warm air down where you are. 

During the summer, on the other hand, turn it to "forward" to create a wind-chill effect as the air moves against your skin and cools you. 

Test, and feel the difference.  If you can't feel a difference, then it probably doesn't make any difference which setting (forward or reverse) you use.

Some fans don't have a so called "forward" or "reverse" setting.  Instead, while looking up at such a fan, it rotates clockwise or counterclockwise. 

So, folks want to know, 'Do I set it on clockwise or counterclockwise?' 

Unfortunately, this question has no consistent answer, because some manufacturers orient the blades so revolving clockwise sends air down, and others orient their blades oppositely, so revolving clockwise sends air up.  The real answer, again, is to stand under the fan, and switch the fan first in one direction and then the other, until you feel the effect you want.

Further Reading:

Fans FAQ, Lamp Depot

Energy Note by Subrato Chandra, University of Central Florida

Q:  What is a dream? I have always wondered but I have no clue.  (Madline, Gulfport, Mississippi)

Q: Why do dreams sometimes seem real? For example, if I fall in a dream, it can wake me.  (Rajesh, Chennai, India)

"The Aerial" conceived and designed by William Samuel Henson  Hand-colored lithograph by W. Walton, printer, 1843, courtesy the Library of Congress.

A:  "Dreams are the little dramas our minds make up when the 'self' system ['me'] is not keeping us alert to the world around us," says dream researcher G. William Domhoff, professor at University of California, Santa Cruz.  That's the simple definition of a dream. 

Moreover, dreams are thoughts that seem like real experiences because we perceive the thoughts with the same mental apparatus used to interpret inputs from our senses, when those senses respond to stimuli from the real world.  Also, a dream seems real because we are the main actor strutting the dream stage, and that actor often gets emotionally involved with the story. 

We don't actually have to be asleep to dream; we can "drift off and suddenly realize we have been dreaming," Domhoff says.  "Two careful studies have shown that people are awake (by EEG criteria) during these episodes."

Since nobody else can witness a dream, it is necessarily something we remember and then report.  So, in a sense, a dream is a memory.

By the way, dreams probably have no purpose.  They may just be absent-minded doodles the brain engages in to while away the night.  "We are thinking creatures," Domhoff says, "because thinking is a valuable adaptation, but that doesn't mean all forms of thinking have a function."

Trivia (from Domhoff's FAQ)

• People, after age 10, dream about 4 to 6 times a night.
• Recurring dreams are common.
• Dreams don't contain much about the events of the day. 
• Almost everyone sometimes dreams someone is chasing or attacking him.
• Blind people dream; their dreams don't involve seeing things, but rather tasting, smelling or touching things.
• Dreams are often about things that bother or preoccupy us, like an upcoming test or the one you love.
• We probably forget 95 % of our dreams, because we're not paying attention to them as we dream.
• Children under 9 years of age don't dream much.

He felt that his whole life was some kind of a dream and he sometimes wondered whose it was and whether they were enjoying it.    Douglas Adams, The Hitchhiker's Guide to the Galaxy

Further Reading:

Frequently asked questions by G. William Domhoff and Adam Schneider, University of California, Santa Cruz

The dreams of blind men and women by Craig Hurovitz, Sarah Dunn, G. William Domhoff and Harry Fiss

Readers' Answers:

•  In a waking state, we are conscious of the world because our sense organs send nerve signals to the brain, causing various areas to become active in response. Activity in, say, the motor areas of the brain can cause nerve signals to pass to the muscles, and cause movement. However just thinking about particular sensory inputs — a favourite song, for example — can cause areas of the brain to activate, just as they would with the real thing. Thinking about exercise, without actually moving your muscles, can still activate relevant brain areas, so mentally rehearsing an activity like playing a piano or kicking a ball can actually improve your performance.

  In the same way, dreams cause activation of various parts or the brain in much the same way as "reality" activates them, so it is really not surprising that dreams can be incredibly "real". If you fall, sensory signals from the balance organs in the inner ear activate areas of the brain that interpret the motion as a fall, and send neural signals to other parts of the brain to generate an alert state. If you fall in a dream the same areas of the brain are activated, and send off "alert" signals just as in a genuine fall.
  
  Geoff Shaw, Melbourne, Victoria, Australia
   

• Dreams are just a type of memory. When we are awake, the brain is flooded by sensory information and any memories or thoughts we have are a minor part of our total brain state. This allows the brain to know which is real, and which is a memory, simply by majority rule.

  When we sleep however, most our normal sensory pathways are blocked. The brain has little reality to compare the memory to. As a result, our memories become the brain's dominant reality. Once you wake, and real sensory data starts to flood the brain again, we instantly switch to believing the dream was only a dream, and not reality.
  Curt Welch, Vienna, Virginia
   

• Dreams are a look into our own minds. During the day we peer out at the world. At night, when we go into R.E.M. sleep, we get a clear look inside our mind. Our brains know what touching feels like, what it is to taste and to hear. Those feeling and images are replayed while we sleep.
  
  Morgan Parker, Hackensack, New Jersey

(Answered Oct. 2, 2006)