From the TED-Ed YouTube channel:
Humanity has long been looking at the universe and asking the big questions: How did it begin? How will it end? Cosmologists are searching hard for the answers, but where do they even start? The answer is light. Pete Edwards outlines the six unique messages that light carries which, when put together, disclose a stunning amount of information to astronomers.
Lesson by Pete Edwards, animation by Bevan Lynch.