NOVA Home Find out what's coming up on air Listing of previous NOVA Web sites NOVA's history Subscribe to the NOVA bulletin Lesson plans and more for teachers NOVA RSS feeds Tell us what you think Program transcripts Buy NOVA videos or DVDs Watch NOVA programs online Answers to frequently asked questions

The Light Stuff


Einstein's Big Idea homepage

Launch interactive The Light Stuff

Einstein was enthralled by light. Even as a teenager he pondered its properties. At 16, he imagined what it would be like to chase, catch up with, and ride on a light beam. When he started thinking more seriously about light, he questioned the thinking of his day—that it traveled through a medium dubbed "ether," and that its speed was determined by how fast its source moved through this mysterious substance. Einstein realized that the speed of light—about 186,000 miles per second—is constant whether it comes from a moving source such as a speeding car's headlights or an unmoving source such as a ceiling light. But here's the catch: The speed of light is constant only in a vacuum, a place where there's no matter, like the vast emptiness of space. Here on Earth, the speed of light can slow down. To see if you can identify what ordinary objects in your house can kick light into a lower gear, click on the image at left.—Karen Hartley


Note: This feature originally appeared, in slightly different form, on NOVA's "Einstein Revealed" Web site, which has been subsumed into the "Einstein's Big Idea" Web site.

  

Send Feedback Image Credits
   
NOVA Home Find out what's coming up on air Listing of previous NOVA Web sites NOVA's history Subscribe to the NOVA bulletin Lesson plans and more for teachers NOVA RSS feeds Tell us what you think Program transcripts Buy NOVA videos or DVDs Watch NOVA programs online Answers to frequently asked questions