Saturday SAVY, Day 3 – Observing the Cosmos (5th/6th)
The final day of Observing the Cosmos began with a short review of cosmic expansion and our balloon demonstration from Day 2. This led into a hands-on Hubble Law observational activity where students plotted galaxy distances (comparing known distances to angular size) against recessional velocities (derived from measured redshift) and compared our results to Hubble’s original trend. Overall, our measurements trended similarly, but we found several outliers. This was a great opportunity to
discuss sources of error, such as measurement technique, ambiguous features in images, or misidentified spectral lines, and allowed for a discussion on why repeated measurements and careful methods matter.
Next, we switched gears to Mars landers and rovers. After watching Perseverance’s entry, descent, and landing sequence, students took on an engineering challenge: the Mars Egonaut Landers. In teams and with a fixed kit of materials, they designed landers to protect an egg payload during deployment. Teams were highly creative; three out of six egg landers survived the test. We discussed design improvements and emphasized that iterative testing and redesign are essential for real missions.
To finish the day, we briefly reviewed telescope types and built cardboard refractor telescopes. During testing, many students noticed the image appeared upside down. That observation led to a brief explanation of how a converging lens inverts the image at the focal plane before magnification. We then took the telescopes outside and tested them from the steps of Wyatt — even simple cardboard refractors with inexpensive lenses can be effective observing tools.
Thought Inspirations:
- What evidence supports the idea that the universe is expanding? (More distant galaxies appear to recede faster; redshift increases with distance.)
- When our Hubble-style measurements showed outliers, what could cause those errors? (Measurement mistakes, image quality, or misidentified spectral features.)
- What stages protect a Mars rover during landing? (Entry, parachute deployment, powered descent/retro rockets, and final touchdown or sky crane/tethering systems.)
- Why did the image through the refractor telescope appear upside down? (A converging lens inverts the image at the focal plane before magnification.)
- How did testing and redesign help teams improve their Mars Egonaut Landers? (Iterative testing identified failure modes and led to design adjustments for better protection.)
To The Parents:
It was an absolute pleasure spending time with your children. Seeing them make new acquaintances, collaborate, and solve problems was a highlight. Each student was sent home with The Astronomy Book: Big Ideas Simply Explained, which covers many of the topics we explored during the three days (i.e., spectra: pp. 124–126; blueshift/redshift: p. 159; Hubble and cosmic expansion: pp. 174–175; Mars landers/rovers: pp. 320+). I hope this book helps your child continue exploring the wonders of the universe.
I also promised to follow up on questions I couldn’t answer during class. Although there were too many to list, here are a few we selected with short answers:
- Why is wavelength represented by the Greek letter lambda (λ)? Greek letters are commonly used in science and math. Lambda corresponds to “L” and may have been chosen to represent “length” or “light,” though the exact historical reason is unclear.
- Why can’t we leave the gas-discharge tubes on for long? These tubes have a limited operating life and can overheat if run continuously. We use short bursts to prevent damage and allow cooling time between uses.
- What gases were in the tubes? We observed spectra for gases such as hydrogen, helium, neon, krypton, argon, and nitrogen.
- How is the James Webb Space Telescope (JWST) different from Hubble? JWST has a larger primary mirror (more light-gathering power) and is optimized for infrared wavelengths. Infrared light penetrates dust better than visible light, letting JWST see objects that Hubble (primarily a visible-light telescope) cannot.
Thank you again for letting me share the wonders of astronomy with your young scientists!
