….or maybe twice, if you happened to be in the right place in 2004. The planet Venus, as seen from the Earth, is passing in front of the sun for several hours tonight — an event which occurs in pairs about eight years apart, less than once per century. The next one is in 2117.
The first hour and a half of the transit was conveniently visible from our front porch.
The safest way to do solar astronomy is to project the image on a surface, such as this sheet of paper taped to the wall: