Rachel
About
Khan Academy on a Stick
Why cepheids pulsate
Why Cepheids Pulsate
Cepheid variables
Cepheid variables 1
Why cepheids pulsate
Why gravity gets so strong near dense objects
Your browser does not support Flash or HTML5 video. You can:
upgrade your browser
install Flash
try this direct link
If the above player doesn't work,
try this direct link
.