What did you change in the model?
Labs / Astronomy
Expanding Universe
Space itself is stretching, carrying the galaxies apart. Slide the scale factor to run the expansion forward and back, then click any galaxy to see how far away it is, how fast it is fleeing, and how its light gets stretched toward red. Notice that the farther a galaxy sits, the faster it recedes — that steady ratio is the Hubble constant.
Labs / Astronomy / Expanding Universe
Expanding Universe
Space itself is stretching, carrying the galaxies apart. Slide the scale factor to run the expansion forward and back, then click any galaxy to see how far away it is, how fast it is fleeing, and how its light gets stretched toward red. Notice that the farther a galaxy sits, the faster it recedes — that steady ratio is the Hubble constant.
Why it matters
Why explore this?
Astronomy uses patterns in light and motion to explain objects we cannot touch directly. This model lets you change one part of a space system and see what the evidence would look like.
Explore
Try the model
d —v —z —H —
Investigate
Questions to test
Predict first, try it in the model, then use what you observe to answer.
What to try
- Click a nearby galaxy, then a distant one. Which has the larger redshift z, and why?
- As you push the scale factor higher, do the absorption lines slide toward red or toward blue?
- Pick three galaxies at different distances. Does the implied Hubble constant H come out the same for all of them?
- Crank H₀ up. What happens to a distant galaxy’s recession speed — can it approach the speed of light?
- Run the scale factor below 1 into the past. Do the galaxies crowd together toward a single point?
Explain
Make sense of what happened
Look for a cause-and-effect rule: what did you change, what responded, and what stayed the same? Astronomers use those patterns to infer how distant systems work.
Check
Before you leave
What visible evidence changed?
What rule could explain that change?
If you can answer all three using evidence from the model, you understand the main idea. If not, return to Explore and change one setting at a time.