Transit of Venus app

The animated simulation means you can refine your skills before June 6. Credit: COSMOS

The Transit of Venus phone app allows users to do with the touch of a screen what astronomers risked life and limb to achieve in the past.

The rare event in which Venus appears to pass across the face of the Sun was hotly pursued in the 18th century as a means of accurately measuring the Astronomical Unit – the distance between the Earth and the Sun – using trigonometry.

However, for various reasons we were never able to be in the right place at the right time to successfully make a precise measurement.

Now on June 6, once and for all – and in solidarity with those astronomers who braved rough seas and typhus plagues to do the very same – we can finally use the transit of Venus to calculate the Astronomical Unit.

Never mind that we were able to come up with an even more precise method and measurement (149,598,000km) during the 20th century, when no transit occurred. This is about finishing off what we started.

The Transit of Venus phone app was developed by Dutch astronomer and app developer Norbert Schmidt, and the project was spearheaded by not-for-profit organisation Astronomers Without Borders.

The way it works is quite simple: while you are (safely) viewing the transit, you touch the screen at the moment of ingress (when the disk of Venus appears to enter the disk of the Sun) and egress (when Venus leaves the Sun). Your phone will vibrate to confirm your input has been recorded, the timing of which will be sent to a global database along with your exact GPS location.

If you’re worried about stage fright, don’t be: the app allows you to practice to your heart’s content using a simulator in the lead up to the real thing. The simulator even tells you how close you came to the exact time, so you can better refine your skills. And don’t worry if you never quite get it right in practice – the collated data from all of the participants will be averaged to account for human error.

Sure, we’ll be figuring out what we already know – but this app is far from useless. It’s a celebration of the incredible distance spanned by science and technology in just a century. Who knows what they’ll be doing to mark the event in 2117?

The Transit of Venus phone app is available for both iPhone and Android, and it’s free.