No, This Weather Really Blows

I have been teaching introductory meteorology and climatology courses for 23 years.  Read on for the most common misconceptions that my students have regarding science:

 

1)      Draining water spins differently in the Southern Hemisphere than in the Northern Hemisphere

It is true that there is an apparent force caused by the earth’s rotation called the Coriolis Force or Coriolis Effect that does cause rotation in large high and low pressure systems.  It is also true that these large rotating systems spin differently in each hemisphere (low pressure systems spin counter-clockwise in the NH while spinning clockwise in the SH).

What is NOT TRUE is that the Coriolis Force causes rotation in a sink or toilet bowl.  The earth can only rotate an object once per day.  Any body rotating much faster than once per day has forces that dwarf the Coriolis Force.  Water draining in a sink certainly spins at a much higher rate than once per day.  In reality, draining water can spin in either direction in either hemisphere.  Flushing toilets are a particularly bad example because the water there is forced in a specific direction by the jets underneath the rim!

For more information please see the excellent explanation titled Bad Coriolis from a former graduate professor of mine at Penn State.

2)      Rubber tires keep you safe in your car from lightning strikes

It is true that one is relatively safe in the car from lightning strikes.  However, the tires are NOT the reason.  Surprising to most is that the metal frame of the car actually keeps the occupants safe inside!

Electricity will flow along the surface of conductive objects such as metal or water.  This is known as the skin effect or Faraday cage effect.  That means that the lightning will flow along the outside of the car and eventually into the ground.  This is why one should never step outside a car with a live power line touching the vehicle and one should avoid touching anything inside the cabin that may be connected to the outside such as door handles, radios, shifters, etc.  Rubber tires offer much less resistance to lightning than the atmosphere it is passing through so if the lightning bolt can overcome the air, tires are a piece of cake!

Watch a car get struck by lightning!

 

3)      Heat lightning is caused by hot, humid summer evenings

It is true that hot, humid conditions are favorable for thunderstorms.  It is also true that lightning is caused by a thunderstorm.  However,  hot, humid air itself cannot generate lightning and there is no such thing as heat lightning!

When a lightning bolt passes through the air, it rapidly heats that air which causes the air to expand.  The rapid expansion generates a sound wave known as thunder.  Light travels 186,000 miles per second while the slow poke known as sound only travels at 1/5 miles per second.  (As an aside: if one sees lightning and then counts the seconds until hearing thunder, every five seconds equals one mile of distance between the observer and the lightning.)  Because of its tremendous speed, light from lightning can travel very far and very fast and is easily seen many miles away.  However, sound may never reach one’s ears.  The result is visible lightning but no audible thunder or what many people would call “heat lightning.”

4)      It is only possible to balance an egg on the fall or spring equinox

Many people believe that on two days of the year (fall and spring equinox) the earth has no tilt and one can balance an egg.  If one can balance an egg on the equinox, then one can balance an egg on any day!  The earth’s “tilt” is 23.5 degrees every day of the year.  Contrary to myth, the earth does not “lose its tilt” on these two days.  The equinox is special because every location on earth gets 12 hours of day and 12 hours of night.  That’s it!

Visit this link to avoid getting egg on your face!

5)      Low pressure sucks air into its center

Wind is caused by various horizontal forces.  One such force known as the pressure gradient force (PGF) causes air to move away from higher pressure and toward lower pressure in an attempt to equalize horizontal air pressure differences.  Simply put, higher pressure systems are blowing air outward.  Lower pressure systems are not sucking the air inward.

Moral of the story:

If somebody tells you “this weather really sucks”, you need to correct them by saying “no, this weather really blows.”