You might have heard that today’s a pretty special day, astronomically speaking. Venus is in transit between Earth and the Sun today, which is a once-in-a-lifetime event. Today only, right before sunset in the United States, if you look up at the sun, you’ll be able to see the silhouetted Venus passing between us and our life-giving star. And due to the differences between Venus’s solar year and our own orbit around the Sun, you’ll have to wait a hundred years until this event happens again.
In other words, if you’re American, you don’t want to miss this if you have any curiosity about the heavens at all. And luckily, there’s an app that will help you make sure you don’t.
The app is called Venus Transit, and it’s free on the iOS App Store. It’s pretty simple: you plug in your location, and the app spits out to you when the transit will start and end.
There’s more, though. During the transit, the phone app enables you to participate in a world-wide experiment: when the measurements of the times of contact from across the world are combined, the distance to the Sun may be found. In fact, the reason we know the distance from the Sun to Earth is because of the transit of Venus across the Sun back in 1769, when scientists around the world pooled their knowledge after the observation to answer a question that finally put into perspective just how small we really are in the grand scheme of things.
Of course, knowing what time to check out the transit is only part of the equation. You also have to be able to watch it safely, without burning your eyes out. Here’s a decent guide on how to do just that.
Can’t make the spectacle? Check out NASA’s live stream of the transit of Venus, live from Mauna Kea, Hawaii.