LOS ANGELES, CA (Catholic Online) - The transit is the product of a periodic alignment between Earth, Venus, and the Sun. To observers, Venus will appear as a tiny black dot moving slowly across the face of the sun over the span of several hours.

Such events are rare, occurring only every 121 to 105 years on a predictable pattern that repeats every 243 years. In plain English, this will be your only chance to witness this event, as the next transit will occur in December of 2117. 

Ancient astronomers did not observe transits of Venus, although they understood the motion of the planet quite well. Astronomer Johannes Kepler was the first to accurately predict a transit of Venus which occurred in 1631, although no European scientists could observe it because it occurred during night in Europe, and no expeditions were sent to Asia where it was visible. 

Still, Kepler was undaunted because he understood the transits occurred in eight-year interval pairs. Accurately predicting the second transit in 1639, a number of scientists observed the phenomenon. Using triangulation, scientists calculated the distance to the Sun. This calculation helped modern astronomers to appreciate the vast size of the Solar System.

Now, you can be a part of history by witnessing this most rare of celestial events. 

How to view it.

First, get the precise time for the transit at your location. The transit will begin and end at different times depending on your location on the globe. You can check that by visiting this site.

Second, viewing of the Sun is very dangerous and can cause temporary or permanent blindness unless safe viewing methods are used. 

Never look directly at the Sun with the naked eye. 

Never look at the sun through an optical device such as binoculars or a telescope as blindness will result. 

It is only safe to look at the sun using specially designed glasses (sunglasses won't work, don't use them), no. 14 welder's glass, or through a device with professional-grade solar viewing filters. 
An alternative and popular way to observe the sun is via "pinhole projection." An observer simply makes a pinhole in a card then allows the light from the pinhole to shine on a parallel flat surface.
 
So, get your observing time, choose your method, and prepare to be a witness to history!

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