Grade Level

High School




Nathan Sanders, Kristen L. Cacciatore

Lesson Summary

In this lesson, students learn about current research into the forces acting on galaxies in our universe, including gravitational forces that attract galaxies to each other and a mysterious force that is pulling galaxies away from each other. Applying Newton’s Laws, students describe the motion of galaxies and the forces between galaxies that govern those motions.

Upon completion of this lesson, students will be able to: 

  • describe forces acting on galaxies.
  • compare the magnitudes of gravitational forces between different celestial bodies using Newton’s Law of Universal Gravitation.
  • discuss action-reaction force pairs in the context of force between galaxies.
  • describe hypotheses related to dark energy and the formation of galaxies.


Science and Engineering Practices:

SP5, SP7

MA Science and Technology/Engineering (2016):

HS-PS2-10(MA), HS-PS2-4

NGSS (2013):


Common Core Math/Language Arts Standards:



Newton's Universal Law of Gravitation, cosmology, dark energy, galaxy, gamma ray bursts, gravity

Educator SoundBites

"I had a blast teaching this lesson! Even though I was familiar with the topic from my own experience in college, I learned from the material as well. I am SO happy I used this in class--the lesson has definitely stuck with my students."
Michelle Smith, Coronado High School, Lubbock, TX

Lesson Documents


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Download PDF View Google Doc

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