Robert Hawkes suggests some apps for informal science learning.
The portability of tablets and smartphones enhance informal science learning in ways that are challenging in more formal settings. Efficient app distribution networks allow scientists and organizations to develop innovative apps without the cost of developing distribution networks. Tablets are easily shared for collaborative learning, and the touchscreen interface is a natural way in to interact with images and simulations.
Imagine being able to take a full planetarium into the outdoor night sky, and have it guide you to identify and find celestial objects. Astronomy apps like SkySafari  do that and more. You enter a search term (e.g. Andromeda Galaxy or Polaris), and arrows guide as you turn your tablet to locate the object in your local sky. The three models (basic, plus, pro) range in price from £1.99 to £27.99, with versions for both Apple and Android devices. The plus and pro give more celestial objects and higher precision simulation over longer time periods. This allows you to see how the moon will rise over Stonehenge on a date in 2500 BC, or watch a solar eclipse from a lunar perspective. The pro and plus versions allow control of many telescopes using the separately purchased SkyFi adapter.
Apps can use the microphone, camera, compass or accelerometer built into the iPad and iPhone for hands-on science investigations anywhere. For example Multi Measures  [£1.49] has an easy to use decibel meter so even young students can check noise levels. The app's tesla meter allows measurement of the three components of the magnetic field, while the seismometer allows measurement of accelerations. The app also includes timer, level, and an angle tool.
Leafsnap  [free] is an innovative tree identification app for Apple devices. You use the camera to take a picture of a leaf against a white background, and the app will propose identification. The project is a joint effort of the University of Maryland, Columbia and the Smithsonian Institution, and although the species provide best coverage for North America the app richly demonstrates an idea that could be applied to many areas of science.
You can safely investigate chemistry by discovery using the Thix Chemist  [£2.99] app. After selecting from a variety of beakers, test tubes, flasks, etc., you add chemicals and visual effects illustrate the reactions. Tools include a pH indicator, thermometer and match to test flammability.
Physics Pad HD  [£2.49] is an engaging way to develop intuition for mechanical interactions. After drawing objects of various shapes, connect them with ropes, rods, springs and gears, and apply physical properties such as mass, friction and elasticity. Running the animation shows how the objects interact. It is possible to record and plot parameters, and simulations can be shared with other users. Both Physics Pad HD and Thix Chemist are available for Apple devices only.
The tablet experience is ideally suited to interacting with images. Earthlapse  [£0.69] transforms your iPad into a seat on the International Space Station with breathtaking time lapse video. 3D4MedicalImages  [free] provides stunning 3D images of everything from red and white blood cells in a blood vessel to a flea about to bite.
Zite  [free] creates a personal magazine adjusted to just your interests. After selecting keywords, the app creates a frequently updated emagazine using online sources. The final result feels surprisingly professional and integrated. While you don't need to use a tablet to watch the TED talks  [free], the app provides a wonderful viewer experience for these inspiring and informative talks, and there is rich coverage of science and science policy topics. Zite is available for Apple devices only, while TED for both Android and Apple devices.