HAd a look on google earth sat website
1. When were these pictures taken? How often are they updated?
Our images are photographs taken by satellites and aircraft sometime in the last three years. The images in Google Earth are updated on a rolling basis.
2. Are Google Earth images captured in real time? No, they aren't. Our images are photographs taken by satellites and aircraft sometime in the last three years.
http://earth.google.com/faq.html