Have you ever pondered the movement of a star A planet or a galaxy up in the night sky Have you ever wondered why the sound of a siren Is constantly changing as it passes you by
It's good to have many questions About the world that you face That's how all of human kind's Discoveries are made
The sound of that siren and light of that star Both are ever changing, it depends on where you are In relation to the source of sound or light alike The frequency that you receive very well might
Cause sound to become lower in pitch Or light to red-shift This change in observed frequency Found by Doppler, the physicist
Just as the sounds of sirens change As they come and go The light from other galaxies Helps us come to know
The universe is vast in size Growing all the time As shown by red-shifting light That's come to meet our eyes