======Elastic Band Universe======


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**Materials: **{{$demo.materials_description}}\\
**Difficulty: **{{$demo.difficulty_description}}\\
**Safety: **{{$demo.safety_description}}\\
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**Categories:** {{$demo.categories}}
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**Alternative titles:** Expanding Universe Model
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====Summary====                   
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====Procedure====  
  - Take a long rubber band and mark several evenly spaced dots along its length to represent galaxies.  
  - Hold one end fixed and slowly stretch the other end.  
  - Observe how the dots move farther apart as the band is stretched.  
  - Measure how far each dot moves compared to its original position.  
  - Show that more distant dots move faster (they cover more distance in the same amount of stretch).



====Links==== 
The Rubber Band Universe - Libke's Earth & Space Systems: 
{{youtube>4AlfL7Y0KHI?}}\\


📄 Modelling the Expansion of the Universe - Cheryl Harper: [[https://www.cpepphysics.org/wp-content/uploads/2022/08/Student-worksheet-cosmological-redshift.pdf]]\\

====Variations====
  * Try stretching the band from the center instead of one end to show expansion is the same from any galaxy’s viewpoint.  
  * Compare a slow stretch versus a quick stretch to represent different rates of expansion.



====Safety Precautions====
  * Do not overstretch the rubber band—it may snap and cause minor injury.  
  * Keep the rubber band away from faces when stretching.




====Questions to Consider====
  * What does each dot on the rubber band represent? (Galaxies.)  
  * Why do more distant “galaxies” appear to move away faster? (Because the stretch adds proportionally more distance between widely separated points, illustrating the Hubble–Lemaître Law.)  
  * How does this model illustrate the cosmological principle? (Expansion looks the same from any chosen reference galaxy.)  
  * How is this model limited compared to the real Universe? (The Universe expands in three dimensions, not just along a line; galaxies themselves do not expand.)