RETROGRADE MOTION OF MARS

The retrograde activity of the planet Mars is discussed in my book, Unraveling the CHRISTMAS  STAR Mystery.  Basic astronomy is addressed in the book to allow readers background information. By learning a little about astronomy, the lay reader will better understand the celestial birth announcement of Jesus Christ.

Since Mars is further from the Sun than Earth, and it’s speed slower, Earth occasionally passes the planet.  Ancient astronomers didn’t understand why that happened. They thought Mars traveled backwards for a short period of time.  The loop the planet makes in that apparent backward path is called “retrograde motion.”

Retro-  refers to “backward.” The Second College Edition,  The American Heritage Dictionary defines the astronomical meaning of retrograde as: “Having a direction of motion opposite to that of the earth on its axis or of the planets around the sun.”

To give an example of the apparent retrograde motion, let me illustrate  with a common occurrence on earth.

When your car passes another on the highway, if you were in the faster passing car, you would see the slower car traveling in the same direction as yourself as you approached it.  When you were actually passing the slower car, the slower vehicle would appear for a short time to move backwards. As you move further on the highway beyond the slower vehicle, you would observe again that both cars would appear to be moving in a forward direction.

This is the same effect observed when Earth approaches and passes Mars.  The planet can be seen moving forward. As Earth passes it, Mars appears to move backward for a short time.  It does not actually move backward. This is the apparent retrograde motion that perplexed ancient astronomers.

Every planet beyond Earth’s orbit is passed by the faster moving Earth as our planet overtakes and laps them. Mars is the more famous planet for retrograde motion as it is more easily seen. 

An animated diagram/ visualization of that phenomenon can be found online at a website of the University of Colorado at Boulder. That link is: http://www.lasalle.edu/~smithsc/Astronomy/retrograd.html

The above copyrighted image is used with permission from Cenk E. Tezel.  The composite images of Mars are spaced 5-7 days apart from late October 2011 (top right) through early July 2012 (bottom left). The website address for Cenk E. Tezel is:  http://www.twanight.org/newTWAN/index.asp. 

Enjoy the predawn skies as you spot Venus and Jupiter this week.