On the left: light carries momentum as well as energy, so when it bounces off a mirror the mirror feels a force. This bit of physics is the basis for solar sails, a scheme of spacecraft propulsion. If humans ever make it beyond our solar system, they may be propelled by a solar sail. The Planetary Society is trying to build one.
On the right: This is my all-time favorite image taken by the Hubble Space Telescope - but it is not a picture of stars. It's called the " deep field " image,
and it was taken by aiming the Hubble away from the Milky Way, pointing towards a dark patch with no stars....which means (almost) everything you see in that
image is a galaxy! It's a profoundly humbling image - each dot is an entire galaxy of stars!
The Hubble Space Telescope is a spectacular engineering success. At its heart, though, is a fairly simple optical imaging system, a telescope built with mirrors. Although by no means the largest telescope in the world, the advantages of being above Earth's atmosphere have provided lots of important data (and popular, beautiful photographs.)
Lectures this week will be electromagnetism (including Maxwell's equations), and we'll move on to the last topics for this term: electromagnetic radiation, and light.
34.6, 34.7, and 34.8
Home page from weeks 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14
We welcome your comments on the class and this website. Send them to victor dot gurarie at colorado dot edu.
(Many thanks to John Price for the original construction of this page!)