• Closest planet to Sun

• Extremes of temperature:
  Greatest change in temperature from day to night
  (700 °F to -300 °F [1000 F° change]*)

• No appreciable protective atmosphere

• Has craters

• Quickest going around Sun (88 earth days for one revolution)

• Rotation on axis is about 58 2/3 earth days counterclockwise (anticlockwise) which is approximately 2/3 of its revolution rate.

• A Mercury solar day is about 176 earth days (Two Mercury years!).

• Greatest Elongation varies between 18° and 28°.
  NOTE: Greatest Elongation is how far a planet appears in the sky away from the sun. Since Mercury's orbit is inside that of the earth's orbit the number of degrees between Mercury and the sun depends upon where Mercury is in its orbit. The variation in Greatest Elongation is because the orbits of both the Mercury and the earth are ellipses rather than circles. Mercury's orbit is also inclined to earth's orbit.

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      This demonstration is best done with a class, however, it can be done with just
      one child and parent.

• Have one child stand in the center of a clear floor space in a room (or this can be done outside). Have the child be the sun. The parent or teacher will be Mercury.
• Mercury standing about 10 feet from the sun points with one arm directly toward the sun (best done facing directly toward child who is the sun). It is noontime for your nose (or where your arm is). Have other children stand outside of the circle (orbit) you will be making around the sun. You, Mercury, will be orbiting to your right (looking down on your orbit that would be counterclockwise). You, Mercury, will be rotating toward your left side (again looking down on your rotation, spin, that would be counterclockwise). Mercury rotates and revolves at the same time. Hold your arm straight out as you do this!
• When you start out point out that you are not only pointing to the sun but also to the background stars.
• When you are 1/3 of the way around in your orbit you will be pointing in the opposite direction (with your rotation being 1/2) to the background stars, however, the sun will still be above the horizon, to the right and in front of you.
• Continue rotating and revolving. When you are 1/2 way around in your orbit, rotating another 1/4 turn, the sun will be directly to your right. This is sunset on Mercury.
• Continue rotating and revolving and when you are 2/3 of theway around in you orbit you will be pointing to the same background stars as when you started. This is ONE ROTATION OF MERCURY! This is about 58 2/3 earth days.
• Continue rotating and revolving until you are back where Mercury started. You are now facing directly away from the sun and directly away from the first background stars and the time is Midnight for your nose (or where your arm is). It has taken 88 earth days to orbit the sun from noon until midnight on Mercury.
• Continue to rotate and revolve. At another 1/3 of the way around Mercury is back toward the first background stars and the sun is still "behind" you.
• Another 1/4 rotation to the second 1/2 way spot in your orbit places the sun directly to your left. This is sunrise on Mercury.
• Continue to rotate and revolve until at the second 2/3 spot in your orbit Mercury is againg facing away from the same background stars as when you started.
• Continue rotating and revolving until you are back at the BEGINNING. You, Mercury, are now facing the sun again and it is noontime after 176 earth days (88 earth days plus 88 earth days)! It has been a long time but you, Mercury, can now have LUNCH again!

• Repeat the process a second time having one child (or group) count the number of revolutions of Mercury around the sun (2) and another child (or group) count the rotations of Mercury on its axis (3).

  HINT:

  Draw a picture of the orbit of Mercury and place a circle in the center for the sun and another circle on the orbit to represent Mercury and an arrow pointing to the sun and lable this position 1. Go around counterclockwise and add position 2 1/3 of the way around with the arrow pointed in the opposite direction. Then add position 3 at 2/3 of the way around with the arrow pointed back to the position 1 direction. Then add a new circle for Mercury just outside position 1 and lable it position 4 with the arrow pointed in the opposite direction (away from the sun). Add a new circle for Mercury just outside position 2 and lable it position 5 with the arrow pointed back to the position 1 direction. Continue to add a new circle for Mercury just outside position 3 and lable it position 6. And then a "7" to position 1. Write in "88 earth days" and "176 earth days" at positions 1 and 7. Also write in 1/3 at positions 2 and 5 and write in 2/3 at positions 3 and 6.

  Don't worry, someday when I update this page I will include that diagram! Have fun and enjoy playing "Mercury and the Sun."