Every so often I see a free app that is just dying to be used as an iPhone demonstration. The candidate for today is the American Museum of Natural History app called Cosmic Discoveries.
When you open the app, you see an image of Saturn. It's a bit crinkly, so you dive in for a closer look, dragging your fingers apart to trigger a zoom. What you'll find is that the image is composed of many hundreds of pictures that can be expanded to near full screen proportions. The zoom goes almost literally to infinity. Some of the pictures are historical photos of observatories or scientists, while many others are striking images of the planets and deep space objects taken by some of our best observatories, or the Hubble or Spitzer Space Telescopes.
You can explore the images and the attached information for hours. Alas, all things are not perfect. The app doesn't support the iPhone 4 Retina display. Another big foul up is that you're given the opportunity to share any image with someone via email, but when the image arrives, text is plastered across the middle of the image suggesting that the recipient download the app, too. It's hard to believe that the people who want you to enjoy the grandeur of the universe would deface their own images for some cheap promotion, which could have been handled in the text of the email and not in front of the image.
I hope that rather glaring fault gets fixed, but even so, this is a really cool program that you can explore at no cost. You're bound to learn a few things, and the gigantic zoom is just the thing to show off your iPhone. There's no iPad-specific version, and the app requires iOS 2.2.1 or later.