Vito Technology’s Solar Walk iPad app costs £1.99, and it focuses on our solar system. It lets you view and scale 3D representations of the Sun, planets, comets, and asteroids, view information about, and (in most cases) images of these objects, and view the solar system (or a planet and its moons) in motion. This impressive iPad app provides a good introduction to the solar system for younger students as well as newcomers to astronomy.
After the app's gorgeous opening screen, which depicts an artist's view of the inner solar system, the app zeroes in on Earth, showing satellites and their orbits around it, continents, vegetation, clouds, and seas, along with the lights on our planet's night side when you rotate it (by sweeping your finger across the screen).
One fun feature of Solar Walk is the time slider along the right hand edge, coupled with the digital clock in the upper right corner. By setting the clock for minutes, hours, days, months, or years and engaging the slider, you can make the Earth rotate (and watch artificial satellites in motion, at least at the slower speeds). If you expand the view by pinching, it will show the Moon in motion around the Earth as well. You can either control the motion by hand, or set the slider in motion by sweeping your finger upwards or downwards and letting go.
Your personal transporter
At the lower left of the interface there’s a Search button. This will transport you elsewhere in the solar system: To the Sun, the planets (Pluto is included as such), dwarf planets and asteroids (Ceres, Makemake, Haumea, Sedna, Eris, and Eros), and comets (Halley's Comet, Hale-Bopp, Borrelly, and Ikeya-Zhang).
Clicking on the information icon for a planet brings up some general information about it, various figures, some info on its internal structure, and a list of science missions to the planet in question.
By using the slider and clock, you can set these objects in motion as well, so you could watch, for example, the globe of Mars rotate (surface features are marked, and there's a 3D depiction of the Curiosity rover at Gale Crater). Alternatively, you can watch Jupiter's cloud belts rotating, and its four large moons in orbit – or the pear-shaped nucleus of Halley's Comet releasing clouds of gas and dust as it rotates. Expanding the Sun view shows you the planets in motion, although its scale is such that the inner planets vanish when you expand the view to encompass the outer worlds.
Also within Search are tabs marked Satellites, Geography, and Stars. With Satellites, you can zero in on specific Earth-orbiting artificial satellites, the most notable being the Hubble Space Telescope and the International Space Station (ISS). Clicking on a satellite name/icon will take you to a close-up view (a detailed 3D representation) of it in space.
By rotating a satellite and using the time slider, you can make it seem like the satellite is orbiting the Earth, with the ground, ocean, or clouds passing beneath it. (This works better with the ISS than with smaller satellites). As with planets and other objects, you can access an information page and image gallery.
The Geography tab gives you a choice of four locations: Mars, Earth, the Moon, and Venus. Clicking on one gives you a list of features, both well-known and obscure, in alphabetical order, which you can visit on the planet’s rotatable globe with a further click.
On the Earth map, most large cities are shown, although there are some notable omissions. New York, for example, seems to have vanished, as does Puerto Rico, Honolulu, and Dublin.
The Stars tab takes you to selected stars. They're shown in their true colours, more or less; for instance, Sirius is bluish, while Barnard's Star is reddish. They're all depicted at the same size – although you can adjust their distance (and therefore, their apparent size) there's no scale, so you wouldn't know that Sirius is much larger than Barnard’s Star by looking at them. They're all shown as single stars, whereas many are double (as is the case with Sirius) or triple (like Rigel Kentaurus, aka Alpha Centauri).
The astronomical data you can call up for each star does indicate which are multiple stars, as well as their mass and radius compared with the Sun – if you know how to read it. And although most bright stars are shown, as well as many fainter ones, once again there are some notable omissions, like the brilliant stars Antares, Rigel, Spica, Deneb, and Canopus (the third brightest star in the sky).
At the top left is a Share button that lets you send a screenshot to email or Facebook, tweet it, save it to camera roll, print it, and rate or gift the app.
The Movies section presents educational animations of some (mostly) basic astronomical phenomena. They include size comparisons of planets, and videos on the Earth's cycles, zodiacal Constellations, and more. These are brief and basic, but do impart useful information for people new to astronomy.
Solar Walk also runs on an iPhone, with the same basic features and functionality. Although it’s fine on an iPhone, the iPad's larger screen only serves to enhance the experience.
This is an impressive little app with some gorgeous image galleries. There are some curious foibles and omissions when it comes to Solar Walk's geography and star search features, but this app boasts some smart videos, search functionality, and social media integration – with a nicely modest price tag to boot.