Tech WondersPlay

Space, GPS & MapsAstronomy

Looking Into the Past

You see the Sun as it was eight minutes ago

The sunlight on your skin left the Sun minutes ago. The stars at night are older still. How far back can a look go?

You'll find out

  • How long sunlight takes to arrive
  • How a laser measures the Moon
  • The oldest light anyone has seen

Why it matters

Every picture of the sky is a picture of the past. Knowing why turns a look at the stars into time travel.

About 3 min6 interactive slides · 5 questionsLesson 270 · Zone 30

Play this lesson

Free to play in your browser or on iPhone

More in this zone

  1. 262Genetic AlgorithmsEvolution Inside a ComputerNASA evolved an antenna that no engineer would have designed
  2. 263MechanicsLift a Car With One HandPulleys spread a heavy load across many ropes
  3. 264Ensemble LearningThe Wisdom of the Crowd800 fairground guesses, averaged, nailed an ox's weight
  4. 265HearingThe Sound Only Teenagers HearWe lose the highest notes as we age
  5. 266Hacking HistoryILOVEYOUA love letter infected tens of millions of computers in 2000
  6. 267Learning ScienceThe Memory PalaceMemory champions store lists by walking through imaginary rooms
  7. 268Machine LearningLearning From ExamplesMachines learn rules nobody wrote down by seeing examples
  8. 269Deep LearningHow a Machine LearnsA model improves by following tiny slopes toward smaller mistakes