Retrograde and direct motion

High school (ages 12+)
Space & Astronomy

Name:

Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/retrograde-and-direct-motion

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. What is the planetary retrograde cycles?Mars exhibits retrograde motion approximately every 26 months, lasting about 10 weeks

Retrograde Motion: The apparent backward movement of a celestial body in the sky from Earth's viewpoint due to relative orbital speeds.
Direct Motion: The apparent forward movement of a celestial body in the sky, consistent with the general direction of orbital motion.
Heliocentric Model: A cosmological model with the Sun at the center of the solar system, around which planets orbit.
Epicycle: A small circle whose center moves along the circumference of a larger circle (deferent), used in geocentric models to explain retrograde motion.