Why does it have to rain?

So we’re all in the car yesterday, and it is pouring down rain. Buckets of it. And my son asks “why does it have to rain now?”

“Because the clouds are full,” my wife answers. 

“That’s no fair,” replies my son.

This got me thinking. I’m familiar with the basics of the water cycle – I had to learn it in second grade. But, I was a little fuzzy. What actually causes rain?  And so, invoking the power of the Internet, I went to NOAA.

If you don’t recognize the name, NOAA is the National Oceanic and Atmospheric Administration. They’re a federal agency tasked with, among other things, weather forecasting and climate monitoring.   And on a SciJinks page titled What makes it rain?, they reminded me of some stuff I’d learned back in second grade and forgot.

See, we all know that heat makes water evaporate.  And warm air can hold more water than cool air. This warm air condenses around dirt and dust and pollen in the air, making clouds (or fog, depending on altitude).  

How long those clouds last is a function of air temperature, because cooler air will make water condense faster. When too much water has condensed to remain airborne, the water falls.

Voila!  Rain!

So why did it have to rain yesterday?  Because there was a lot of water in the air, and it was cold.


Do only people get chickenpox?

I haven’t the slightest idea what prompted this question.  My son was watching Peg + Cat on PBS Kids, and they weren’t even talking about chickenpox.  But he looks over at me and asks “do only people get chickenpox?”  And you know what?  I had no idea.  So, since I have the internet at my disposal, I decided to do a little research.  Shockingly, the Centers for Disease Control are a veritable goldmine of information on the subject.

Chickenpox  is the result of an infection by the varicella zoster virus, which is part of the Herpesviridae family of DNA Viruses.  It is one of 8 types of herpesvirus that infect humans.  The others are:

  • Herpes simplex viruses 1 and 2
  • Human herpesvirus 6 and 7
  • Epstein-Barr virus
  • Human cytomegalovirus
  • Karposi’s sarcoma-associated herpesvirus

Varicella zoster virus only infects humans, so technically only humans can get chickenpox.  However, there is also a Simian Varicella Virus that infects other primates, causing extremely similar symptoms.

According to the CDC, in the early 1990s an average of 4 million people get chickenpox each year in the United States alone.  Between eight and eighteen thousand of these cases are severe enough to require hospitalization, and between 100 and 150 individuals die from it annually.  The good news is that we’ve had a vaccine for it since 1995, which works by introducing a less virulent strain of VZV to the body so that the immune system can learn to fight it off.  Since it was introduced, there’s been an 82% reduction in chickenpox infections, and a 71% reduction in hospitalization rates for infections.  Deaths from chickenpox have declined by98.5% in individuals under the age of 20, by 96% in adults between 20 and 50, and by 49% in individuals over the age of 50.