Mars

 

August 11, 2006

 

http://cainer.com/ericfrancis/aug11.html

 

Dear Eric,

 

I received this PowerPoint presentation regarding planet Mars on the e-mail this morning… will it really appear the size of a Full Moon this month?!

 

Wow!

-- Maria

 

 

Dear Maria:

 

Yes, that PowerPoint is going around like then next great thing. But personally, I don't get what they're on about.

 

Mars never appears as big as the Full Moon. Quoting from a reputable astronomy web page:

 

"The Full Moon has an apparent magnitude of about -12.5 and Mars, at its brightest, has an apparent magnitude of about -2.8. This means that the Full Moon is about 10 (-12.5 - (-2.8)) magnitudes brighter than the maximum brightness of Mars. Each five magnitudes means 100 times more flux. Since 10 = 5 x 2, about 10,000 (100^(2)) times more flux reaches our eyes from the full Moon than from Mars."

 

In other words, even with Mars at its brightest, the Full Moon is 100,000 times brighter.

 

The truly big close pass of Mars to the Earth was during the Mars retrograde of 2003, the year everyone cooked in France, and the first summer of the Iraq quagmire. Now, every year, someone says it's gonna be even bigger yet.

 

Mars is visible when it's retrograde, or close to retrograde. This is because retrograde means "close to the Earth." But Mars is not retrograde now and it won't be for another year. Indeed, it's so close to the Sun right now, and on the other side of the Sun, that it's invisible. The Sun is aligning closer to Mars, getting not further.

 

My only explanation for this PowerPoint's extreme popularity is that with so many wars on the planet, people are obsessed with Mars and how beautiful it is. I highly recommend adding a little Venus to the mix.

 

ERIC FRANCIS