One of the rarest celestial events viewable from Earth will occur Tuesday -- the planet Venus will make a trek across the face of the sun. Such an event has only been observed six times in recorded history, and the next occurrence won't come until 2117, so space buffs are gearing up for the big show.
One way to stay tuned -- and also help scientists record Venus' voyage -- is by using an app called VenusTransit. With this app, which is available on Android and iOS, amateur astronomers can join the ranks of historic explorers like Capt. James … Read more