Our Expanding Universe - SMAP Live

While Sir Edwin Hubble is often associated with discovering that the Universe appeared to be expanding, it was Vesto Slipher who found around 1912 that the spectra of galaxies show a shift toward the redder end of the visible spectrum. Hubble correlated Slipher's measurements with distances he measured by other means to formulate his now well-known Hubble's Law. Doppler shift, red shift, blue shift, expansion of the Universe would become familiar terms in cosmology.
Our Expanding Universe SMAP lesson first explores the Doppler shift using sound, by measuring the changes in frequency from a stationary source by an observer in motion. Students use the free downloadable app, Phyphox and an on-line tone generator to collect data and, from their frequencies calculate the wavelengths of the approaching and receding frequency, and the velocity of their mobile phone in motion.
Invited talk and discussion by Purdue Physics and Astronomy Professor Dimitrios Giannios leads students, applying the same methods and mathematics used with their phones, to calculate the sub relativistic velocities of galaxies characteristic in our expanding universe.
The session wraps up with Edwin Hubble's discovery of the relationship between velocity and distance.
Two versions of our lesson, teacher guides, and supporting PDFs are available here, bit.ly/SMAPSelectedLessons.
Doppler Effect intro video (modeling Doppler effect with sound), is also on our channel, bit.ly/DopperBackground
Timeline
0:00 Introduction
1:15 Poll 1 - What are your thoughts about sound?
4:42 Intro to Phyphox
6:20 Breakout
8:38 Demonstrating the Phyphox technique
14:50 Setting up to calculate wavelength
22:30 Velocity of the phone in motion
24:32 Recap of sound waves
32:14 Poll 2 - Thoughts about light and space
34:20 From sound waves to light waves
38:55 Measuring expansion with redshift
49:50 Hubble's discoveries
52:25 Balloon expansion demo
58:05 Looking back in time
The creative thumbnail for our video was created by Jonathan Sullivan-Wood, Purdue Physics and Astronomy grad staff. Thank you Jonathan!